Adhesive Removers and Flooring

Whether the floor is going through an asbestos abatement or there is just a standard rip-up of old floor covering it may be tempting to use a chemical adhesive remover to clean the substrate. However, there are a lot of warnings from adhesive and floor covering manufacturers about this practice.

ASTM F 710 Concrete to Receive Resilient Flooring states; There are a number of commercial adhesive removers that will properly remove adhesive residue from a subfloor; however, there are concerns that these products may adversely affect the new adhesive and new floor covering.

The Resilient Floor Covering Institute’s (RFCI’s) recommended work practices for removal of ex-isting resilient floor coverings states; These products may leave a solvent residue within the sub-floor that can adversely affect the new adhesive or floor covering. Thus, the warranties provided by the manufacturers of new floor covering materials will not cover instances where subfloor conditions damage their products or effect their installation.

Armstrong Floors states; Many adhesive removal products contain solvents that leave a residue within the subfloor. This residue can negatively affect the new adhesive and bleed through the new floor covering. The warranties provided by manufacturers of new floor covering materials will not cover instances where existing subfloor conditions damage their products or affect their installation.

Tarkett states; Tarkett does not recommend the use of solvent-based adhesive removers. These products leave a residue within the substrate that can adversely affect the new adhesive and flooring material.

The problem is that chemical adhesive removers are made to dissolve old existing adhesive, and will impregnate the subfloor that will eventually work its way back out of the subfloor. If moisture is present in the substrate, which it always is to some degree, and the new flooring material is non permeable, either hard surface flooring or carpet tiles, a reaction is most likely inevitable that will cause a failure in the installation that is not covered by the flooring manufacturer.

If any residual is left behind on the substrate there is a risk that the new adhesive will be af-fected. Another potential problem is when adhesive remover is used to remove black cutback residue and the soup of old adhesive and the removal chemical settles into cracks in the con-crete. 

 

 Even if the cracks are patched this residue can work itself up to the surface and discolor the new floor from the bottom up. Flash patching the subfloor does not create a bar-rier to stop the migration of these products up through and affecting the new flooring and adhesive.

Mapei has just introduced two new products that will encapsulate the adhesive remover.

First, the slab must be cleaned using Mapei Planiprep SA which is a scouring agent that chemically etches the concrete for the next step.

Second, the slab is then treated with Plani-prep ET. Planiprep ET is a penetrating epoxy subfloor treatment that penetrates deeply into the concrete and strengthening and creating a suitable surface for application of all Mapei adhesives that are approved for use on non-porous substrates. If the slab would need smoothed out, prime the Planiprep ET with Mapei Primer T and skim coat over the Primer T.

Also, the system above provides subfloor moisture control for concrete slabs up to 12-lbs. Calcium Chloride and 90% Relative Hu-midity without the need for shotblasasdting the concrete.

Special Thanks to JJ Haines for the information

How Long Does it Take Concrete to Dry

 

A concrete surface may look dry, but the slab can still contain sufficient moisture to cause problems when covered. The term “concrete moisture” is understood to mean the total water used in the concrete batch, plus curing water, minus the water bound in hardened cement due to hydration. The amount of concrete moisture can be considerable. In practical terms, several pounds of water must evaporate from every square foot of concrete for the slab to be considered adequately dry for floor finishes.

Drying begins when water is no longer available at the exposed surface. If concrete is moist cured by sealing in the original mix water with wet burlap or plastic sheets, drying will begin when these covers are removed. Spray-applied curing membranes are somewhat breathable, and therefore, drying begins shortly after the membrane is applied. However, curing compounds can drastically reduce the drying rate and significantly extend the drying period.

A method of testing the moisture condition of a concrete slab is to measure the relative humidity of the air in the concrete pore system. This is done by placing a relative humidity probe into a hole drilled in the concrete. The relative humidity achieved within a concrete slab depends on a combination of factors including the initial water-to-cement ratio, drying history, pore structure, and concentration of soluble ions in the pore water solution.

Curing is one of the most important steps in concrete construction, because proper curing greatly increases concrete strength and durability. Concrete hardens as a result of hydration: the chemical reaction between cement and water. However, hydration occurs only if water is available and if the concrete’s temperature stays within a suitable range. During the curing period-from five to seven days after placement for conventional concrete-the concrete surface needs to be kept moist to permit the hydration process. New concrete can be wet cured using soaking hoses, sprinklers or covered with wet burlap, or as we see today, can be coated with commercially available curing compounds, which seal in moisture (can result in high rH and lower Calcium Chloride readings) and must be removed prior to patching the floor or installation of the floor covering. Any type of sealer or curing compound on the concrete surface can interfere with all of the non-destructive moisture tests. These surface treatments can also interfere with the adhesion of patching compounds and adhesives. Manufacturers will recommend that the surface treatments be removed before the flooring application.

Temperature extremes make it difficult to properly cure concrete. On hot days, too much water is lost by evaporation from newly placed concrete. If the temperature drops too close to freezing, hydration slows to nearly a standstill. Under these conditions, concrete ceases to gain strength and other desirable properties. In general, the temperature of new concrete should not be allowed to fall below 50 Fahrenheit during the curing period.

Concrete hardens and gains strength as it hydrates. The hydration process continues over a long period of time. It happens rapidly at first and slows down as time goes by. To measure the ultimate strength of concrete would require a wait of several years. This would be impractical, so a time period of 28 days was selected by specification writing authorities as the age that all concrete should be tested for strength (28 days does not mean it is dry). At this age, under the right conditions, a substantial percentage of the hydration has taken place.

If the drying period of concrete is critical then it should be protected from re‑wetting. Rainfall on the concrete slab, infiltration into joints and wetting of subgrades will extend the drying period. For floors, ideally the concrete should not be placed until the building has been enclosed.

The speed of the drying process is a function of many things, such as the following.

• Thickness of the concrete: Thicker slabs dry more slowly.

• Concrete density: Dense concrete will dry more slowly.

• Moisture content: More water content requires more time to dry.

• Temperatures of the concrete and the air above it: Heat energizes water molecules.

• Dew point temperatures of the air above the concrete: low dew points will encourage migration of the water

from the concrete.

If shorter concrete drying times are necessary then reducing the water-cement ratio is recommended. The use of admixtures can assist in reducing the water-cement ratio and maintaining the workability required. Reducing the water-cement ratio below 0.4, as no further reduction in the drying time was obtained. A water-cement ratio of 0.5 will generally allow drying within three months, and slabs with water-cement ratios greater than 0.6 will take an very long time to dry and cause adhesives or floor coverings, or both, to fail due to high moisture permeability.

The drying environment will also affect the time required for the concrete to dry. As lower relative humidity or higher temperature environment will allow faster drying. An air-conditioned space or one which is heated should reduce the drying time. Caution must be exercised if the surface is dried rapidly by the use of equipment such as heaters and blowers due to the increased risk of shrinkage cracking at an early concrete age. Also, while the surface or upper layer of concrete may indicate moisture levels acceptable for the installation of finishes, the moisture present at greater depths will re-distribute following covering of the surface. Depending on the drying time allowed, this may result in unacceptable moisture levels beneath the flooring and cause future problems. Measuring moisture content at the concrete surface (Calcium Chloride) will generally not give an accurate indication of the final moisture content, and whether the concrete is dry enough for the application of a floor finish or coating.

In new construction the excess water in the concrete needs time and conditions which allow it to dry out before

installing flooring. Placing high solids curing compounds on the slab to hold the water in to cure the concrete. This then prevents the slab from drying properly to flooring installation. An untreated slab with no moisture from the top or from below will take 60 to 90 days to adequately dry at 72 F and 50 % relative humidity. Curing compounds or cold weather can slow this process. If the moisture level in the air is high, water in the concrete evaporates very slowly, or not at all. This slows construction and increases the potential for mold.

An industry rule of thumb for estimating the drying time necessary for concrete floors to reach acceptable moisture content is 1 month of drying for each inch of concrete thickness. So a 6 inch thick slab, may take 6 months to dry sufficiently for flooring. Optimum indoor drying conditions occur at 30% relative humidity and 65to 70 F with constant airflow over the slab surface.

 

Special Thanks to JJ Haines for the information

Common Adhesive Problems

Adhesive concerns surface in all types of situations. Often, we believe that the only role an adhesive plays is to hold down a piece of material. But frequently, circumstances arise to create problems. The following are several of the more common adhesive-related concerns and their possible causes.

Bleeding of adhesives can occur for a variety of reasons.

Excess adhesive, from a trowel notch that is heavier than what was specified by the manufacturer of the adhesive or resilient material, can leave a film of adhesive that is simply too thick. This thick film tends to migrate when subjected to foot or rolling-load traffic.

Open time of the adhesive was not honored. With few exceptions, adhesives are designed to have open time. Open time allows the adhesive to lose some of its moisture and develop body. The professional installer must know how to judge the proper open time in accordance with individual job-related variables, such as temperature, humidity and substrate absorbency.

Moisture problems can impact adhesives within days of their application. The emergence of a moisture condition can cause the adhesive to re-emulsify and ooze.

A maintenance problem, often the result of either stripping the floor or starting the floor maintenance regimen too soon, can cause adhesives to bleed. New floors should not be stripped immediately. Strippers are highly alkaline, and their alkalinity attacks the adhesive – especially when the adhesive is new. Subjecting newly installed resilient materials to excessive moisture, perhaps by aggressively mopping the floor, will create the same effect as a moisture problem if the adhesive has yet to fully cure.

Compatibility of adhesives with the substrate Residues on the surface of the substrate can cause de-bonding, discoloration and adhesive deterioration issues. Any residue left on the surface of the substrate introduces one more variable that can cause adhesive failure. Some common residues, and the concerns they create, are as follows:

Oily residues create bonding and discoloration issues.

Sealers and curing compounds create bonding and adhesive compatibility issues.

Parting compounds create bonding issues.

Overspray of paint creates bonding and adhesive compatibility issues.

Gypsum wall textures/taping compounds create bonding issues.

Solvent spills create discoloration and adhesive deterioration concerns.

Heating oil spills create discoloration and adhesive deterioration concerns.

Existing adhesives can create compatibility problems with the new adhesive.

Bonding failures The causes of adhesive bond failures are varied. Some of the more common situations are detailed below.

Dirt and dust on the surface of a substrate can create enough of a barrier to negatively impact the adhesive’s bond and cause installation failure once the floor is placed into service. Dusty surfaces can also cause adhesives to “ball-up,” which creates a show-through problem in the finished floor.

Residues from sealers, curing compounds and parting compounds serve as just one more layer of a substance that can fail.

Insufficient open time for adhesives usually leads to bubbling, indentation of the material’s surface and adhesive migration.

Excessive open time usually results in a poor bond between the resilient material and the adhesive. This is usually the case whenever there’s a lack of adhesive transfer to the back of the material.

Moisture damage to an adhesive manifests itself in two ways: either in re-emulsification, or in a poor bond of the adhesive to the substrate. Either condition tells you that the adhesive was not allowed to cure. Adhesives that re-emulsify were exposed to moisture prior to the adhesive’s cure, meaning the substrate was too wet to install over. Adhesives that initially cured but were then subjected to moisture will usually de-bond from the surface of the substrate, leaving most of the adhesive stuck to the back of the flooring material

Alkalinity damage appears in two ways: the adhesive will have a crystallized appearance and be somewhat brittle, or it may virtually disappear and leave only a few traces of residue. Alkalinity attack on an adhesive can create the impression that too little adhesive was used. In reality, the adhesive was just eaten up by the alkaline salts.

Adhesives that dry too soon due to the effects of an overly absorptive substrate can cause the adhesive to appear chalky and somewhat crystallized.

Excessive adhesive application Excessive adhesive application is usually the result of the installer using an improper trowel notch for the job. In fact, the trowel is the installer’s single most misused tool. All adhesive manufacturers specify the trowel notch requirements for their adhesives and for the type of substrate to which the adhesive is used on.

So, why is there a problem? If your using a trowel with 1/16″ wide and 1/16″ deep notches spaced 1/16 ” apart, and the specifications for the adhesive required a trowel with 1/16″, 1/16″ deep notches spaced 3/32″ apart, you’d probably question what harm could come from using the trowel that had notch spacing a mere 1/32″ smaller what was specified. How could such a small difference affect an adhesive? The answer is almost 20% more adhesive will be applied to the substrate.

Excessive adhesive applied can be responsible for indentations in resilient material caused by static loads and rolling loads. Ridges may also develop in the adhesive during the rolling of the floor. Other problems caused by the application of excessive adhesive include oozing of adhesive, and bubbles in the floor covering.

The substrate’s porosity often dictates the type of adhesive to use and the amount of open time it requires. Many times, a floor in a renovation project is assumed to be porous when, in fact, the substrate is non-porous.

Rolling flooring into the adhesive I hear a lot of comments regarding the use of a roller. To get excess air out from beneath the freshly laid floor covering, some installers use a broom, a wet towel wrapped around a piece of lumber, a wall roller, their hands, and any number of other means. The bottom line is they are too lazy to carry in the appropriate tool – a roller – to complete the installation in the specified manner.

Why do you think a manufacturer would specify the use of a 100-lb. roller if a 25-lb. one would do the job? The reason is application of a specific, straight-line static load is necessary to force the material down into the

adhesive while maintaining a uniform pressure on the surface of the material. Do you think that could be accomplished with a broom?

Adhesive removal Removal of adhesives must be done with the greatest of care. Some adhesives must be completely removed, while others may be removed to a thin residue. In no case should a new adhesive be applied over the trowel notches of an old adhesive.

Adhesives should be removed mechanically, not by chemical means. Pay careful attention when dealing with old cutback adhesive, as it did contain asbestos. Consult your local authorities on the proper ways to safely remove it.

Chemical adhesive removers are not recommended by flooring manufacturers. The problem is that chemical adhesive removers are made to dissolve old existing adhesive, and will impregnate the subfloor that will eventually work its way back out of the subfloor. If moisture is present in the substrate, which it always is to some degree, and the new flooring material is non permeable, either hard surface flooring or carpet tiles, a reaction is most likely inevitable that will cause a failure. Beware of adhesive abatement companies that are not familiar with the flooring industry and its standards. These firms can leave you with what appears to be a clean substrate even when it is loaded with adhesive remover residues that are not readily identifiable. Other problems Trowel notch show-through. How many times have you walked into a supermarket and gasped at the trowel notch show-through you see in the floor? This occurs when the installer either uses a trowel with the notches spaced too far apart for the adhesive to be used, or his trowel had worn down and was improperly re-notched so that several notches were made deeper than the others. I have seen instances of this so bad that the vinyl composition tile (VCT) was cracked over the ridge the trowel left in the adhesive.

Material subjected to traffic too soon. Sometimes, after an installation is completed, other tradesmen working at the job site are allowed onto the floor too soon. When the entire job is completed and the floor is cleaned and polished with a high-gloss polish, a host of indentations and rolling-load marks immediately become apparent all over the new floor. This occurs because the adhesive was never allowed to cure before being subjected to traffic.

Manufacturers specify that a newly installed floor should be protected from foot traffic for 24 hours and from rolling-load traffic for 72 hours. It doesn’t matter whether the applied adhesive is latex, acrylic or an epoxy – they all need to be protected while curing. Adhesives generally take 5 to 7 days to cure at proper conditions.

 

 

 

Understanding Vapor Barriers

 Anyone that has had to face a moisture problem with a concrete slab understands the damage that excessive moisture can cause. Moisture in concrete can occur from a variety of sources: ground moisture that contacts the slab through either capillary action or as water vapor, high air humidity or drastic changes in relative humidity in its environment, leaking plumbing that passes through the slab, and more. Excess moisture can cause ph changes in concrete that adversely affect adhesives. Even an excess of moisture that was retained from the original concrete mixture will cause problems if the slab was sealed prematurely. Concrete starts wet. The water added to the cement, sand and aggregate mixture is necessary to form a good bond in the concrete, but it is also necessary that the moisture evaporate away from the concrete in order to let the concrete dry and to prevent flooring failures. Adding more water may make concrete more workable but it also means the drying time can increase to unreasonable levels as the rate of evaporation is dependent on a number of variables. While moisture can be added to the slab through a number of different sources, it can only evaporate away through the slab’s surface. It often can’t escape the slab without remediating treatment. In simple terms, a concrete slab in contact with moisture cannot be brought to dry conditions. Something has to stop the intrusion of moisture into the slab. The preventative measure most often used to try to stop these moisture issues is to install a vapor barrier. But what type and where it should be installed has been a subject of much debate. Some feel that vapor barriers contribute to curling in the slab and that simply casting on a granular slab should be sufficient. Others feel a vapor barrier is a critical element to protecting from flooring or adhesive failures, and even some environmental issues, as vapor barriers can prevent moisture-related mold and mildew growth or even block certain gases that can pose a health risk if they accumulate in a home or business. Any material that resists moisture passage is a vapor barrier, a term often used interchangeably with vapor retarder. Few are true barriers as they still have the ability to let water vapor pass through. This is often expressed as “perms” that allow for categories of permeability. The degree of permeability that is acceptable may depend on the application – for example, a water vapor permeance less than 0.3 perms is generally recommended but for residential use, a higher permeance rate is considered acceptable. What seems to be crucial is that the vapor barrier or retarder under the slab must have a lower degree of permeance than the flooring or floor covering above the slab. Otherwise, the potential for a moisture imbalance can still cause flooring failures over time.

Currently, a vapor barrier is typically applied over a layer of granular fill to try to minimize the wicking effect of ground moisture. Of course, if the vapor barrier is punctured, it will not be effective in preventing moisture migration. Seams must be properly sealed, heavy grade materials must be used where traffic may cause a penetration, and the lowest possible grade of permeance should be used. The concrete slab is then poured directly over the vapor barrier. Prior to the 2000s, a “fill” layer was recommended between the vapor barrier and the slab. But this practice changed as the difficulties of keeping the blotter layer moisture-free became impossible. It must be noted that this practice, though, causes slower drying times because moisture cannot leave a drying slab with the vapor barrier directly under the slab, moisture then has to move to the surface of the slab and evaporate from there. Placing the vapor barrier under the fill layer let contractors float the concrete sooner and appeared to dry the concrete more quickly because the base accepted some of the water from the original concrete mixture

 

Because there are pros and cons to both situations, accurate relative humidity testing is also necessary to be sure slab moisture conditions are ready for the flooring or finish application of choice. Moisture-sensitive adhesives and floor coverings can be just as adversely affected by a moisture level too high in the slab as they can by moisture-wicking problems due to an inadequate vapor barrier. Relative humidity testing can give an accurate picture of what the final result of a sealed concrete slab will be when it is fully equilibrated. There is only one chance to make the best vapor barrier choice, and obviously that is before the slab is poured. For each concrete slab, it is important to understand the best vapor barrier choice based on local conditions, recommended guidelines and careful application.

Special Thanks to JJ Haines for the info

The Wait For Concrete to Dry

 A building project is typically handled in a series of stages, each of which has its own manager. The goal is always to smoothly hand off each segment of a construction project from one manager to the next without any delays. But when moisture-sensitive flooring is involved, there’s one part of construction that can throw a wrench in the process: The concrete slab.

What’s Required to Achieve Successful Flooring Installation?

For flooring installation to be successful: The slab moisture content and pH levels need to be within optimal range;

The slab must be protected from external moisture;

Compatibility of the moisture level in the slab with both the specified floor covering and flooring adhesive needs to be achieved

Moisture-emission potential must be addressed.

What are the Factors That Delay a Slab’s Drying Time?

 

The procedures involved with pouring and drying a concrete slab are guided by many industry standards. But the drying time for each slab is almost impossible to predict. The factors which contribute to the slab’s drying time are unique to each and every installation. The drying time variables include:

The components of the original concrete mixture (water/cement ratio)

Ambient air humidity

Final service conditions

Surface finishes

Functionality of the HVAC system

Floating practices or rewetting

When any of the above-named factors are altered during the project, the concrete may require a longer drying time. Delays to achieving a properly dried slab can throw off entire construction schedules.

 

Is it Better to Wait for the Slab to Dry or Forge Ahead?

Lost man hours and additional costs are just two results of scheduling interruptions on a construction project. But the alternative, which is to push ahead in spite of the slab’s condition, leads to flooring failure. Ultimately, a moisture-related flooring problem is a no-win situation for everyone from the contractors and construction managers to the flooring installers, adhesive manufacturers, and facility owners. Experience has proven, that the results of forging ahead on the installation of flooring before the concrete moisture issues in the slab have been resolved , carries a much larger price tag than playing the waiting game and getting it right in the first place.

 

All Eyes on the Goal, Not the Clock

The ultimate goal in a construction project to end up with an installed flooring system that’s problem-free for the long term. When the construction schedule leaves no room for moisture issues in the concrete to be properly dealt with, there’s a temptation to rush the project and invite flooring failure.

How To Know When the Slab is Ready There are different methods which can help to speed along the drying time of the slab, such as desiccant drying

and surface treatments. But how can the flooring contractor be certain that the moisture levels in the slab are compatible with the moisture-sensitive adhesive and flooring to be installed on the project? An accurate monitoring of the relative humidity (RH) within the concrete slab is the best way to determine when the drying time has been completed. Surface testing only of moisture conditions of a concrete slab, such as calcium chloride testing, aren’t reliable, in spite of the fact that such methods have been commonly used in the industry for years. RH testing is superior to surface-only testing in that it reflects the final RH conditions underneath an installed floor. Supplied with accurate knowledge of a slab’s RH condition, the general contractor and flooring installer will know whether to allow for more drying time to reach adhesive/flooring specifications or to choose a different flooring adhesive or flooring product which is compatible with the slab’s current conditions. RH testing is a great benefit to the construction process, giving everyone involved the information they need to understand that it’s time to either wait or move on to the flooring installation phase of the project.

Concrete Prep

Installation success only happens with thorough subfloor and job preparation. Skipping a moisture test, not removing concrete curing or sealing compounds, not removing old adhesives, or not leveling a subfloor are easy steps to a costly job failure. Burnished or hard trowel finished concrete is a large and growing problem that we are receiving from the concrete industry. With the use of power trowels the concrete finishers are over-troweling the concrete surface, leaving a burnished surface. Burnished or hard troweled concrete is shiny and highly consolidated and presents several problems for the flooring industry. First, the highly consolidated surface severely slows the drying of the slab because the moisture is slow to pass through the consolidated layer. Second, moisture testing that is done at the surface (Calcium Chloride) will yield low readings or false positives due to the retarded moisture vapor flow and the short period of time the test is run. Third, some adhesives, especially epoxies and urethanes, will not be able to achieve a good mechanical bond to the concrete’s surface. These types of adhesives are designed for excessive abuse and require an open slab’s surface to attain this mechanical bond. Concrete curing or sealing compounds – ASTM F-710 states that if a curing, sealing or parting compound is to be used it should be removed. Problems begin as many flooring contractors do not realize that sanding with a buffer will not remove the compound. Sanding will only scratch the curing, sealing or parting compound. Other installers believe that curing or sealing compounds will either walk-off or degrade from either UV exposure or oxidation. While this is somewhat true, the exposure does nothing to the pores of the concrete that is filled by this same compound. These compounds also slow the migration of moisture and retard drying. This is another reason why surface moisture tests must be ground to open the pores of the concrete’s surface. Going directly over a curing or sealing compound is foolish. There have been situations where the residual solvent in a heavily applied cure ‘n seal attacked the applied adhesive about nine months after the installation. Buffing or sanding the surface of the concrete – Installers will give a concrete slab a quick sanding with an 16 or 24 grit open coat sandpaper, thinking they have taken care of anything that might prevent a good bond. On the contrary, sometimes scratching a latent substance that is present on the surface of the concrete will only allow it to de-bond faster from the concrete surface. Situations like these de-bond sometime after the slab is in use and the flooring has been installed. Poorly finished concrete – Poorly finished concrete is generally dusty and very absorptive. Dust will cause the adhesive to ball-up and also to dry too fast. Usually, concrete like this will require a primer to slow the absorption and drying time. Latent substances on the concrete surface – Many times in new construction a lot of mud can be tracked onto the concrete surface. If the mud is clay-like or high in fines it can stick to the surface like it is part of the concrete. A solution for this would be to use a buffer sander to remove this laitance, or a layer of weak powdery material on the surface. Concrete mitigation treatments – Many contractors are automatically planning for moisture treatments from past experiences with moisture. When an installer arrives at the jobsite, make sure he is aware if the slab has been treated for moisture. Otherwise he may disturb the ongoing mitigation treatment. The installer also needs to be aware of is if the slab is non-porous and needs to be treated as such. Other factors the installer should be aware of include whether the job will feature a specialty flooring or specialty adhesive
that needs to be installed over a non-porous substrate. Concrete to have epoxy applied – Some slabs are either going to have an epoxy adhesive used under a resilient flooring product or have an epoxy coating applied. In either of these situations it is necessary to be able to achieve a good mechanical bond between the adhesive and the substrate. Choosing the correct CSP profile – When should you abrade the concrete surface? For proper bonding of concrete overlays and coatings, it’s important to give the surface the correct concrete surface profile, or CSP. To help contractors make this assessment, the International Concrete Repair Institute (ICRI) has developed benchmark guidelines for CSP—a measure of the average distance from the peaks of the surface to the valleys. They range from CSP 1 (nearly flat) to CSP 9 (very rough). As a general rule, the thicker the overlay or topping, the more aggressive the profile needs to be. A skim coat, for example, may require a light CSP of 2 to 4. For thicker self-leveling or polymer overlays, acceptable profiles generally range from CSP 4 to 6. Achieving surface profiles in the higher ranges often requires roughening by shot-blasting or scarifying. With existing adhesives, the majority of the adhesive must be scraped to a thin residue before shot-blasting to prevent the shot from gumming up or bouncing off the surface of the adhesive. Please note to make sure the existing adhesive does not contain asbestos. Asbestos was used in the Black Cutback Adhesives up until around 1983. Do not use adhesive/mastic removers. The purpose of surface preparation is to provide sound, clean and suitably roughened surfaces on concrete substrates. This process includes the removal of unsound concrete and bond-inhibiting films, strength verification, opening the pore structure and establishing profiles suitable for the application of the specified flooring system.

Resilient Concerns

 

I am sure you have heard “The new floor is only as good as what you cover,” and that is certainly the case. Here are problems that can cause a lot of resilient floors to fail.

 

Concrete; Failures that are moisture or pH related continue to be a problem. Testing can detect elevated moisture conditions before they become problems and it can also be another source of income for the professional installer who knows how to do the testing properly. ASTM F 1869 (Calcium Chloride Test) is a test for vapor emissions from the concrete surface and ASTM F 2170 (Relative Humidity Probe method) measures moisture inside the slab. There is no correlation between these two tests. Both provide valuable information about the condition of the concrete. There is a growing awareness of these test methods so it pays installers to learn what testing methods are out there and how to do them.

Patching Compounds; Over watering is the number one cause of patching compound failure. Today’s patches are modified with polymers that give them tremendous strength and bonding power, but the chemistry of these products is compromised if too much water is added to the mix. The finished patch layer will be weaker, not as hard and more porous – three characteristics that can adversely affect the floor covering or the adhesive. Another cause of patching compound failure is applying it in too thick a layer so that cracks or it is not dry when the floor is installed. Check the manufacturer’s specs for how thick the patch can go down because most of them can’t go much over 1/2″ in a single application. Finally, there is a big misunderstanding out there about skim coating in commercial applications directly over an existing floor like vinyl composition tile. Read the book – chances are the patching compound manufacturer does not recommend this procedure, although many dealers and installers think they do. The reason for this is due to rolling loads possibly breaking up the skim coat over the existing vinyl.

Adhesive Residue; In renovation work, failure to remove the old adhesive can cause problems such as indentation of the new flooring, chemical reactions between the old adhesive and the new adhesive, patch blowing off the floor or complete failure of the new adhesive. If you are just pulling up that old floor, skim coating and installing the new floor, your installations are a problem waiting to happen. Read the instructions and you’ll find that the patching compound manufacturer wants most, if not all of the old adhesive removed from the floor before the patching compound is applied. And, don’t use chemical adhesive remover to do the job because they can cause problems later on with the new adhesive. Use mechanical methods to remove the adhesive residue.

Plywood Underlayments; Today, the three most common panel underlayments are plywood, lauan, or fiber reinforced panels. Most resilient flooring manufacturers are no longer recommending lauan as an underlayment. Lauan tends to be soft and susceptible to denting and crushing under concentrated loads such as furniture legs or high heels. Many of these panels have caused severe problems such as discoloration, delaminating and adhesion failures. If you are using lauan, the flooring manufacturer may not cover any failures and the manufacturer of the panel will be nowhere to be found if you have a problem. Plywood is a superior product to Lauan. Real three-ply or five-ply 1/4-inch-thick underlayment products (like Ultraply XL) are readily available today from flooring supply distributors. These branded products come with instructions for how to install them and have a solid manufacturer’s warranty. Fiber reinforced panel underlayments are common in the stone and ceramic industry and are starting to gain popularity for resilient flooring as well. These products remind one of drywall in appearance and in their score and snap method of cutting, but they are designed to be underlayments so they carry the performance characteristics and warranties for use under resilient.

Adhesive Issues; Adhesive selection and adhesive use are often misunderstood in the process of specifying and installing resilient flooring. For example, although it’s tempting to save money and time, you can’t use clear thin spread to install solid vinyl tile. So, before the job is even quoted it is important to match the adhesive to

the job and quote the job accordingly. Once the adhesive is selected, proper application is critical. The trowel is an application device that puts adhesive on the floor and is also a measuring device that precisely meters the amount of adhesive being applied. Every manufacturer has specific trowel notch recommendations. One trowel for everything will not work for you. I have often seen the results of too much adhesive – sheet vinyl with indentations, tile with adhesive oozing between the joints, lumpy, bumpy cove base, stair treads that shifted because the excess adhesive didn’t dry, and epoxy that doesn’t cure. The idea that more is better is a huge mistake to make with resilient flooring products. The cost of a trowel is a tiny part of the installation cost. There is no excuse for not having the right trowel on the job.

 

Seams; There is an art to cutting and seaming products. Seams are what most end users and home owners fear. Today’s products are more flexible and easy to cut, but that does not make seaming technique any less critical. Some products are seamed by the double cut method and others by under scribe or straightedge and butt methods. Knowing the difference can make you or break you as far as the finished installation goes because different products have different cutting methods for making a seam. For example, cutting seams in natural linoleum is different than in vinyl or rubber sheet goods. It tends to shrink in length and grow in width, so linoleum seams are often cut slightly open on side seams and not on cross (end) seams. On the flip side, some of the flexible vinyl and rubber products today work best with a double cut seam and the traditional inlaids work best with recess scribing. In these cases, the seams will be net with no gaps. Where to cut the seam is an issue in the case of patterned materials with a grout line. Do you cut the seam in the middle of the grout line or on the edge? This will vary from product to product. Today’s fiberglass Loose-Lay floors require seams to be double-cut.

Pay attention to the details and refer to the manufacturer’s guidelines. Specialized tools are available for trimming sheet goods and cutting seams so make sure you are ready by having the right equipment. As far as seam sealers, I have seen a lot of split seam failures caused when the seam sealer applicator tip does not penetrate into the seam. This means that the sealer is left only on the surface rather than inside the seam holding the two pieces together. On the commercial side, failures in heat welded seams are often caused by leaving a gap when the flooring is installed so that the welded seam is not as strong as it would be if the two pieces are butted together before welding. Cutting too wide a groove, moving too fast with the welding gun, or having the wrong temperature on the gun are all causes of heat weld failures. Training is available from a number of manufacturers and there is always scrap material to practice on.

 

Maintenance; Maintenance related complaints are almost as frequent as installation complaints these days. I have found these problems are often the result of misunderstandings because of a lack of written instructions, or because someone who sold or installed the material gave the wrong advice. If you don’t know, don’t answer. If you give the wrong advice and something goes wrong with the floor, you could be held liable. For example, cleaning for no wax vinyl is often misunderstood. Soap based cleaners can leave a dulling film, where a mild detergent will not. Another example is real linoleum, where the use of strong alkaline cleaners can cause cracking, shrinking and possible discoloration. Yet another example is cork flooring, a resilient flooring material that acts a lot like wood. Using a lot of water on cork can ruin the floor. In all cases, how the floor is cleaned can cause permanent damage. The use of the wrong chemicals or the wrong cleaning or scrubbing pads can ruin the floor. The best advice to an installer as far as maintenance is, if you don’t know, don’t tell. Somewhere in the manufacturer’s material you bring to the job will be a phone number or website address. Find it and give it to the customer. This is one good time to “pass the buck” to the manufacturer, or back to the dealer so the maintenance is done correctly.

Proper Installation of Solid Hardwood Flooring

 Most all wood floors will have an occasional squeak, pop, or creak. This is considered an acceptable condition that does not make the floor fail to perform. But like a lot of things that go into homebuilding, it’s often the things that the homebuyer doesn’t see that really count. And this is particularly true when it comes to fastening wood floors. It takes the right combination of materials, tools and techniques to properly install a wood floor. Done right, the homebuyer notices only the beauty of the floor itself. Done wrong, the problems stick out like a sore thumb: creaks, pops, moving boards, uneven boards and ugly nail holes. You only have one chance to get it right. So, use care and attention to detail, along with the right materials, tools and techniques, and you’ll win every time.

The subflooring itself can contribute to noises. Particle board is well known for fastener movement and resulting squeaks. Some OSB products have shown low fastener retention as well. When coupled with typical moisture events during construction, OSB subflooring is at risk for producing noises related to moisture-induced thickness swell associated with reduced density and irregular flatness. Plywood on the other hand may show some delamination which affects fastener holding.

 

Since wood flooring is normally placed in homes that are not designed to meet the bare minimum subfloor performance requirements, a system that exceeds the minimum is recommended by NWFA. The APA has a recommended system called a Code Plus System that shows the use of thicker panels, a step above the minimum performance rating. A subfloor system should be sufficiently stiff to allow minimum movement.

 

The NWFA recommends the following for acceptable subfloor/truss systems;

 

1. On truss/joist spacing of 16″ o/c or less, the industry standard for single-panel subflooring is nominal 5/8″ CD Exposure 1 Plywood subfloor panels (CD EXPOSURE 1) or 23/32″ OSB Exposure 1 subfloor panels, 4′ X 8′ sheets.

 

2. On truss/joist spacing of more than 16″, up to 19.2″ o/c, the standard is nominal 3/4″ (23/32″ T&G CD EXPOSURE 1) Plywood subfloor panels, (Exposure 1), 4’ X 8′ sheets, glued and mechanically fastened, or nominal 3/4″ (23/32″) OSB Exposure 1 subfloor panels, 4’ x 8’ sheets, glued and mechanically fastened.

 

3. Truss/joist systems spaced over more than 19.2″ o/c up to a maximum of 24″ require nominal 7/8″ T&G CD EXPOSURE 1 Plywood subfloor panels, (Exposure 1), 4’ X 8′ sheets, glued and mechanically fastened, or nominal 1″ OSB Exposure 1 subfloor panels, 4’ x 8’ sheets, glued and mechanically fastened — or two layers of subflooring. Or brace between truss/joists in accordance with the truss/joist manufacturer’s recommendations and with local building codes. Some truss/joist systems cannot be cross-braced and still maintain stability.

 

The reason for the thicker requirement for OSB is that tests have shown the thicker 3/4″ (23/32″) OSB holds wood flooring fasteners only as well as 5/8″plywood. Better nail holding produces a quieter floor with less movement among boards. Less movement among boards for site finished flooring also produces less finish separation or flaking along board edges.

 

We hear the term, L/360, as the term for the greatest allowable deflection at center span. This means that for a span of 20 feet, the deflection can be just over 5/8″ at center span. Today in order to accommodate the wide-open areas in homes, these and longer spans are typical, thus significant deflection can occur along the length of joists. For less deflection a stiffer joist system is needed, such as L/480 or L/560 and greater. In addition, wider spacing than the traditional 16″ On Center between supporting joists allows for even more variation.

These systems all pass building codes and support the intended loads; however, with hardwood flooring the

expected performance may not be achieved with maximum joist spacing, maximum spans, and minimum thickness subflooring.

The stiffer systems are also generally also recommended for engineered flooring, since these products are normally thinner and add minimally to the strength of the system. Manufacturers have specific subfloor specifications, so always follow the manufacturer’s recommendations.

Prior to the flooring installation, the house environment must be at near occupied conditions. The subflooring should be clean dry and flat. Flat for the minimal framed system may not meet the minimum requirement. For the L/360 and a 20-foot span, the 10-foot deflection allowed can be 1/3-inch, which is more than the 1/4-inch most commonly required for flatness. Further, the subfloor may be flat enough before it is loaded with flooring, furniture, and people, but not after the loads are applied. Again where a minimum system is in place, inform the customer that the final performance may not meet their performance expectation.

 

The wood subflooring materials must not exceed 13% moisture content. Using a wood moisture meter, measure the moisture content of both the subfloor and the hardwood flooring to determine the proper moisture content. The difference between the moisture content of the wood subflooring and the hardwood flooring must not exceed 4% for strip and 3% for plank flooring.

 

The actual flooring fastener can contribute to noises if improperly placed or an incorrect fastener is used. Over driving the fastener has been shown to split the flooring tongue away from the board and compromise the fastener connection. Smooth shanked brads and other small nails don’t hold well and can contribute to noises.

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Before installing 3/4″ Solid Wood flooring, place an approved vapor retarder over the wooden subfloor. Some examples of acceptable vapor retarders over wood subfloors include: An Asphalt-saturated kraft paper such as AquaBar B or #15 felt that meets ASTM Standard D-4869 or UU-B-790, Grade D.

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Before installing 5/16″ & 7/16″ Solid

Wood flooring, place an approved vapor retarder such as a 6 mil poly over the wood subfloor.

Hardwood flooring can be affected by varying levels of humidity within homes. Maintaining the homes air relative humidity levels within the 35–55% range help protects the hardwood flooring. Advise your customers the following; 

Heating Season (Dry): A humidifier is recommended to prevent excessive shrinkage in hardwood floors due to low humidity levels. Wood stoves and electric heat tend to create very dry conditions.

 

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Non-Heating Season (Humid, Wet): Proper humidity levels can be maintained by use of an air conditioner, dehumidifier, or by turning on your heating system periodically during the summer months. Avoid excessive exposure to water during periods of inclement weather.

 

Tips on Solid Hardwood

As a general rule, a 3/4″expansion space must be left around the perimeter and at all vertical obstructions. The thickness of shoe molding is not an acceptable expansion zone.

Random-width plank is laid out with alternating courses varying by widths. Start with the widest board, then the next width, etc., and repeat the pattern.

Layout: Avoid “H” patterns. Stagger end joints of boards row to row.

 

 

Moisture Meters VS Relative Humidity Probes

 As a concrete slab dries, there is a gradual and diffuse process that must take place before it is ready for a flooring or coating application. When concrete is freshly poured, liquid water must evaporate from the surface. As that liquid evaporates, more liquid moves up through the slab to continue evaporating from the surface until only water vapor remains to move through the slab in the drying process. But by its very nature, the process means that a slab‟s surface will be “drier” than deeper into the concrete. And it is the amount of water vapor, or relative humidity that must be monitored in order to meet ASTM standards and to ensure a proper flooring application.

Keep in mind that an uncovered concrete slab will indeed have a relative humidity gradient (typically drier at the surface; much wetter at depth) throughout its thickness until a floor covering is put on top. Under normal conditions, the RH at roughly 50% slab depth will be significantly higher than the surface unless the slab has been down for a long time, and a vapor retarder is directly underneath the slab. This normal relative humidity gradient is why problems occur when relying on the use of surface tests.

 

Concrete “Moisture meters”, no matter what type, fail to provide consistently accurate „moisture‟ readings across the different mixes and densities of concrete. Additionally, other components (metal reinforcing bar, aggregate size and amount, etc.) can cause false indications of „moisture‟ especially with non-pin meters. Pin-type „moisture‟ meters are also not practical for moisture measurement because variable chemical and physical characteristics in concrete can cause false readings due to changes in electrical resistance that have nothing to do with moisture.

 

The calcium chloride test method (moisture vapor emission), and the UK-based „hood‟ method (RH) both have the same problem. They are surface tests and in reality, the surface of the concrete will more closely reflect the RH in the room or building than the conditions down inside the slab.

 

The only way you can get the true “moisture” picture, then, is by putting a probe down into the concrete and actually measuring the relative humidity within the body of the concrete. The industry standard (developed at Lund University in Sweden and adopted by the ASTM) demonstrates that a probe set at approximately 40% of the concrete‟s total depth provides the best indicator of the final equilibration once a floor covering is applied, and an accurate indicator of the conditions that will be in contact with the final flooring or coating.

 

As surface moisture tests, hand held meters (qualitative), or calcium chloride or hood method tests (quantitative) are fine, if recommended by the flooring manufacturer. But if you want the true, critical moisture picture of what‟s happening deeper in the concrete, you have to get below the surface with an in situ relative humidity probe. An accurate relative

 

Special Thanks To JJ Haines for the Article

Avoiding Slab Moisture Problems is Crucial

 In construction, if floor covering fails to remain bonded, it will quickly become the most expensive post-construction nightmare short of an earthquake. Floor covering material bond failures over concrete represent a multibillion dollar price tag to every kind of facility from homes to hospitals. Imaging having to shut down a busy facility, move patients out to another location, remove all objects in the room and then deal with the construction process needed to remedy and replace everything. The downtime costs, frustration levels and legal pursuits are historic. The only thing that is not well known about this problem is why it occurs so often.

All concrete slabs emit moisture in the form of water-vapor from the surface. If the volume of moisture exceeds the dissipation ability of the floor covering placed over it, moisture becomes entrapped between the slab and flooring. In time, the volume of moisture and the chemistry of the substance will destroy the bond of the flooring, resulting in bubbles, seam splits, curling and other physical signs that ultimately result in trip hazards, breach of sterility, and aesthetic and performance loss.

 

Most people in medical building design and construction understand the devastating effect of unwanted moisture moving in through roofing, walls, windows and HVAC systems. In fact, unwanted moisture intrusion like this represents a substantial number of construction litigation cases. Great measures are taken to minimize the potential for roof and wall system moisture, but when it comes to the concrete slab the misunderstanding is actually amazing.

 

When a slab is poured on the ground, it is usually placed over a sand layer that is on top of a plastic sheet or over a sand-bed. This plastic sheet is commonly called a vapor barrier, is better termed a retarder. (You can never stop ALL moisture vapor from entering a building, only minimize its volume to where it’s not a problem.) This measure is taken to reduce the long-term intrusion of moisture from the ground. Underslab vapor retarders however, have no effect on controlling the moisture that was inside the concrete during its construction that still has to escape.

 

The time it takes for a concrete slab to lose enough water-of-convenience to be acceptable to floor covering installations is usually considerably longer than the construction schedule. Building envelopes are supposed to be just that, but cannot become an envelope or internal environment until they are enclosed and the HVAC system is put into operation. It is then that many slabs begin to dry.

 

Those with experience in this realm already know that the floor covering material is one of the last things to be installed in a new facility and in most cases just a few days after the building has become an envelope, if even then. The acclimation of an interior creates an environmental effect on the building that draws moisture vapor out of concrete. How much moisture comes out of a given slab is governed by many variables, beginning with water/cement ratio, followed by surface profile, and ultimately drying time.

 

In most cases, buildings that are under fast track construction schedules are at risk for having all the right ingredients to create a floor bond problem. The American Concrete Institute long ago created a general rule on concrete slab drying.

When it is 70 degrees or warmer with no more than 40 percent relative humidity nor more than a 15 mph wind, concrete slabs will dry at a rate of 1 inch thickness per month. If the slab becomes rewetted anytime during the initial drying process, double that time.

 

The problem with moisture-related floor covering bond failures is discussed by every manufacturer of flooring products and is often a crowd-gathering subject when presented at seminars in the construction industry. The issue isn’t whether or not there is natural moisture to a slab that can affect the bond of the floor down the road; the issue is really whose moisture it is.

Some years ago, the floor covering community governed by the World Floor Covering Association, banded together and published an industry position paper that is easily available at their website today. This paper summarizes very well the complexities involved in achieving floor/slab compatibility but also outlines the responsibilities they feel should be taken by all construction parties.

The owner drives the construction schedule in most cases, and needs to learn that concrete will dry on its own time, governed mainly by the environment. If the slab cannot achieve a moisture condition within compliance for flooring, the owner can elect to prolong the construction schedule or pay for additional costs needed to seal the slab from the surface to render it compliant for safe installation. Those are the only choices.

However, in most cases the awareness of this potential problem is not discovered until the last hour of construction when the floor covering is ready to be installed. The floor covering contractor who is diligent and cares about their own liability, will ensure moisture tests be conducted before laying a single tile on the ground. If the tests show everything is okay, they can proceed safely. If not, it becomes an interesting problem almost immediately. In most cases, it becomes an emotional issue. The flooring contractor wants no liability for a failure and will ask the general contractor to sign off on installation. The expectation is, the sign off will protect them legally from damages if they proceed to install anyway, even over a known problem condition. If the floor contractor refuses to install until the situation is fixed, it leads to delays and sometimes incompletion damages placed on them.

The only way to address the problem is to be proactive in the specification process and to understand the time lines, the environmental conditions, and to have a plan to remediate the moisture condition prior to floor covering installation should test results come back high or unsafe. If the level is low, the allocated funds will not need to be spent. If they fail, meaning the slab needs to be sealed, then the money was already in the budget and the time was put into the schedule to fix the problem correctly. Unfortunately, in most cases the general contractor is blamed for making a bad slab when they are the first to bring up the subject of high moisture test results at the last hour. The general contractor is forced to pay more money to render it compliant for flooring, even though the fault is best contributed to the age of the concrete, not the concrete itself.

Facilities cannot afford to shut down and move out because of the floor problem, and that should be the foremost thought on the minds of everyone in the construction process. If the issue is left to blame on the general contractor or flooring sub, it doesn’t eliminate the risk or the experience of a failure, regardless of fault.

In every floor failure, the owner of the facility would confess that if they had known and understood the risk factor, they would have taken whatever precautions they could, rather than experience a costly failure and in some cases biological growth of bacteria and mold which can destroy a building. Hospital administrators are forced to lay off staff, move patients into other facilities and are at a loss to understand what happened, who is at fault and what to do next. The frustration levels are understandable, often unbearable.

So what to do? First, understand that the problem of floor moisture is one of nature, not necessarily some particular party’s fault. Second, consider the construction schedules, concrete mix designs, placement specifications, building acclimation issues and floor covering sensitivities. If there clearly is risk involved, the owner needs to have the architect specify a treatment that is proven effective to solve the problem and then pay for it. The solution has to be viable, which is another complicated subject best saved for another time.

In many cases where a plan for remediation has not been thought of and budgeted beforehand, the owner forces the architect, general and subcontractor to absorb the cost. Their attitude is that they paid to have a building made, and that’s that. But somewhere in the mix, because they are driving the construction schedule ultimately and not giving the concrete time to dry, they are forcing an unrealistic expectation. Building owners, architects and contractors need to be on the same page when it comes to this rather misunderstood but all too common problem. That starts with admitting it exists, believe it or not. Too often one hears, “We have never had a

moisture problem” only to discover that they just haven’t heard about it, for it may take a year to occur, another year to figure out what happened, and yet another year to learn enough to finally make it a legal pursuit.

The problem is far more complicated than the physics. New slabs don’t dry fast even with all the precautions taken to put vapor retarders under them. But who gets to pay for resolving the issue is an ongoing argument that occurs every day somewhere in our nation, as well as in other countries. This thing affects the homeowner to members of the Fortune 500. No one and no organization is immune. If the architect and owner agree to specify and install a remediation system then it should be done and its costs become just another part of the building. If they didn’t plan for it in budgeting but discover the potential for a problem, then again the owner should pay for a solution or perhaps give the building an unrealistic year to dry out. The moisture belongs to the owner, not the architect, general or floor subcontractor.

It’s when nothing is done that the flooring contractor is put in to a NO WIN situation and may be forced to install and risk the liability for a failure. Likewise for the general contractor, they get blamed for doing something wrong and look for the cheapest solution possible whether it’s viable or not since they have to pay for it, leaving once again the owner to suffer the consequences of downtime.

There is no excuse for a floor failure, other than ignorance. The physics are not complicated, but the social issues have always been and that is why moisture related floor covering failures continue to occur.

 

Special Thanks to JJ Haines for the Information