Don has spent 28 years in the flooring industry honing his craft and accumulating a great deal of experience and know-how along the way. Having installed carpet, vinyl, hardwood, commercial flooring, tile and stone, he is a valued authority on a wide range of flooring subjects.
His Moto: “The question you ask is free…the question you don’t ask is expensive!”
So, in an effort to save you some money, we’re going to ask the questions…
· The substrate was not tested properly (moisture / alkalinity testing).
· Inadequate substrate preparation.
· Improper material mix.
What can be done to address these issues?
· Test the substrate in accordance with the NFCA Floor Covering Reference Manual instructions.
· Follow proper rules of preparation as per the industry standard.
· Read the instructions of the material you are applying. Products vary in many ways from manufacturer to manufacturer. There is no one way for all.
What are the most important things to consider when specifying cementitious underlayment over:
1. New concrete
Confirm the concrete is dry. Concrete cure time is not the same as dry time. While fresh concrete may cure to design strength in 28 days the dry time can be as long as one month (or more) per inch of slab thickness depending on the concrete mix. There are two tests that are supported by our industry:
a. Anhydrous Calcium Chloride Test (ASTM F1869)
b. Relative Humidity test (ASTMF2170)
Details and specifications for these tests can be downloaded online at www.bcfca.com or found in the NFCA Floor Covering Reference Manual.
2. Existing concrete with old flooring still attached
The ideal scenario is always to start with a newly prepared, clean and stable substrate. Leveling compounds have limitations and they too are only as good as what they bond to. Old adhesive residue or contaminants on the slab surface can interfere with short and long term bond strength of new adhesive. This often results in the floor covering bubbling up, shrinking, gapping or releasing.
If in doubt, clean the surface and get down to the grey stuff (for example shot blasting) before installing new product.
3. Concrete on grade.
As with new concrete moisture is the concern. Concrete on grade comes with the risk of wicking moisture up from the ground beneath. Low-lying areas such as Richmond and Delta are notorious for this.
Cement levelers can be sensitive to hydrostatic pressure if they are encapsulated and not allowed to breath. Always moisture test the slab and understand the leveling compounds limitations before applying.
4. What advice can you give to specifiers when choosing a concrete underlayment?
Choose a product with a track record, good rep support for the intended area (geographical) of use and with clear instructions regarding correct use and application. Know what floor covering application / product is going to be used, as this will influence product choice. For example, concrete levelers for floating floor applications do not have to be as strong as those intended for use in glue down applications, i.e. wood flooring glued directly to a concrete underlayment exerts a lot of stress on the floor system below as it shrinks and expands naturally through the four season cycle. Linoleum shrinks and expands too…same issue.
Selecting the right cement-based underlayment should be determined by intended use (type of floor covering and type of installation) and the budget. If budget alone dictates the choice of product then your risk of problems and failure will be high.
5. Can you share a story involving a product failure and the resulting effects?
Our industry is full of failures - mostly caused by the same simple mistakes being repeated and often due to deadlines forcing bad decisions. Floorcoverings are “the” most visible form of finish, and basically the last thing in a project next to touchup paint and a set of keys. So, why don’t we spend the time and money on installing them properly?
I recall a project of significant size, where a new slab exhibited a high moisture reading even after 14 months of dry time. The moisture readings were monitored and registered at above maximum levels. The general contractor and owner were presented with the problem and advised to either wait until the moisture readings came down to an appropriate level or add a moisture control system. Both options were rejected and the installation went ahead anyway. The floorcovering was a commercial grade Linoleum. Two years later, it had to be removed and replaced due to a health and a safety hazard…health because of a mold issue and safety because of the many trip hazards where the flooring was lifting. The solution would have added a 3% cost overrun on the flooring budget, but they opted for the risk. The result was10 times that amount and took months of disruption to correct.
When the time came to replace the flooring, an Epoxy Moisture Control System was used to remediate the moisture issue followed by a new floorcovering installation. Currently on year 6 of its life, the floorcovering is performing to its full potential without any further issues.
6. Is temperature and relative humidity a concern with concrete leveling products?
Yes - temperature and humidity are always a concern with concrete leveling products. Portland cement products normally require an ambient temperature of 50 degrees F and rising during installation and after for a period of 48 hours, in order for its ingredients to properly hydrate and reach sustainable strengths.
7. Are primers a must when choosing a product?
In most cases, “Primers” are required. But this will depend on the manufacturer and the product. Think of “Primers” as the vanilla cream that sticks the 2 wafers of an OREO cookie together…would the wafers stick together if the cream wasn’t there?
8. Fly Ash concrete - is this a concern? If so, what leveling product / type should be specified and why?
Fly Ash is a residue of the carbon arc furnace process and usually refers to ash that is produced during the combustion of coal. It is often used to supplement Portland cement in concrete production and Portland cement based patching/repair materials and has been around for many years.
Some authorities have expressed concerns over the possibility of higher levels of contaminants. Most manufacturers of fly ash materials have disputed this position and have mixed the fly ash with proportional levels of other materials to bring the fly ash ingredients to a non-hazardous level.
The two types of fly ash that are readily used are Class F and Class C fly ash. If there are concerns and issues over how much fly ash is in a concrete mix, I would recommend asking the concrete company what the mix in question consists of and then contact your local underlayment representative to confirm their acceptance of that application.
The bottom line is don’t just assume the leveling compound will bond. Do a bond test and if in doubt ask!!
9. What’s new in concrete leveling technology? Has there been anything you’ve seen that’s proven/tested that you’ve been impressed with?
Recently, I have been impressed with the advanced use of polymer technology in some of the newer self-leveling products now available. With these new products, the benefits are faster curing and turnaround times.
10. Finally, if you could change one thing with regard to concrete leveling in the flooring industry, what would it be and why?
If I could change one thing, it would be to gain cooperation of all of the manufacturers in the industry in agreeing on a uniform/mandatory procedure(s) for surface preparation guidelines.