Flooring Forensics: Installing new flooring over old floors – Oct 2019

Floor Focus Interview with Lew Migliore

Installing new floorcoverings over old floors isn’t anything new. Carpet over carpet, tile over tile, sheet vinyl over sheet vinyl-all of these installations have been done. The key to success is the integrity of the existing flooring, existing installation and of the substrate.

Years ago, one of my mentors developed a peel and stick mesh material for installing carpet over carpet. Shaw also had one of these products, and a few of the installation methods still exist. It was intended primarily for commercial carpet being installed over existing carpet to save money and time. The existing carpet did require cleaning prior to the installation of new carpet. This could also conceivably be accomplished with carpet tile using tabs to install carpet over carpet or over hard surface flooring.

If you’re gluing the new flooring over the top of existing flooring, the old flooring must be clean of all contaminants and bond breakers. If you’re planning to leave old carpet down, the old carpet must be cleaned first. Also, if carpet is to be installed over carpet, there must be a component to allow it to adhere, unless the installation is to be done with tackless strip.

However, with new floating flooring systems and flooring materials that don’t use adhesive out of a bucket, this poses new questions as to how viable and prudent it is to do this. Both hard and soft surface flooring is capable of being installed this way. So, let’s ask and answer some questions regarding installing new flooring over old existing flooring.

Q: What drives the decision to install new flooring over old flooring?
Time and money are the drivers, as they are with most flooring installations, especially that of commercial flooring. The belief is that it is faster and cheaper to keep the old flooring in place and install over the top of it. The thought is you don’t have to take the time or spend the money removing the old flooring. You still have to clean and prep the surface if you plan to glue anything to it, even if the installation is to be a floating flooring material.

Q: How do you determine if the old floor has to be removed prior to installing the new floor?
If the old flooring is solidly installed, shows no signs of coming up and is above grade, it may be a good candidate to install over. If the flooring is on or below grade concrete, then you have to think again about doing this.

An example is an old vinyl tile floor; it may or may not contain asbestos, may look like it’s down tighter than two coats of paint and research may tell you it’s been down for decades without any issues on the old substrate. So, now you remove all the old floor finish, prep the floor and install the new flooring material. A year later the new flooring is reacting by coming loose, raising or developing some other distortion compromising its adhesion.

What you’ve done is place a moisture vapor retarder, or even a barrier, over an existing floor that was intact despite moisture below and in the slab. Once the floor has been covered, you’ve changed the dynamics and instead of the moisture vapor venting, it is being trapped. The result is both the old and new flooring are now coming up.

If the old floor was vinyl asbestos tile with cut back adhesive, you’ve just stepped into a quagmire. Remember the time and money you thought you saved? Well, you’ve just escalated the repair costs. Not only does all the flooring have to go, but you’ve also got to do asbestos abatement and then install a complete moisture mitigation system. The cost will be astronomical, and the time to fix everything will be extensive. Don’t think that floating a floor over old flooring in this situation will be better as it likely will not. The reaction may take longer, but the result will be the same at some point in time.

Q: When it comes to transitions into other rooms or with outside doors, how do you work around the increased elevation of having a second flooring layer?
You’ll have to raise the elevation with some type of shim material or leveling agent. If angling down, you’ll have to remove substrate material and patch and undercut door jambs to make the transition. At any rate, some type of substrate adjustments will have to be made. The job will dictate what has to be done, and you’ll have to figure out how to do it in order for the transition to work. A good installer will know how to make the transition work.

Q: What can be used to make sure old flooring patterns or grout lines don’t telegraph through the new floor?
The old flooring must be cleaned of any coatings so the leveling material being used to fill grout lines will bond, and there are a number of leveling materials on the market for this purpose.

Q: Are there squeaking issues to consider?
If you’re floating a floor, there are always going to be squeaking issues to consider, whether it’s installed over an old floor or an existing substrate. Since all floating floors use some type of an engagement system and they will all move to some degree, there is always the chance of squeaking or crackling noises. This is a very common issue. A simple fix is to put talcum powder in between the joints of the flooring material to stop squeaking.

Q: If you have to remove an old floor, what steps must be taken to prep for the replacement?
In this case, all of the old adhesive must be removed. The substrate, if concrete, must be tested for moisture-if wood, it may require a sealer. The floor prep guidelines specified by the manufacturer must be followed.

Q: Are there other factors to consider in a commercial environment?
Flooring over flooring guidelines should be the same. The biggest difference is the amount of traffic the flooring will be subjected to and whether installing flooring over flooring makes sense relative to any risks that may be involved. So, the type of flooring being installed over existing flooring must fit the application. In a commercial installation, there is always a risk when installing flooring over flooring, but the feasibility must be determined on a case by case basis.

Q: From your experience, what is the most common mistake made when installing one surface over another?
The biggest mistake by far is not considering the real consequences of installing new flooring over old. Again, this is especially significant with old slab on or below grade. Covering the old flooring with anything, whether a membrane of some kind or new flooring, is a gamble at best. If the building is older, the first step is to go outside and look at the gutters/building drainage, grading, irrigation system and perimeter of the foundation. If water is capable of hydrating the slab from any, all or a few of these sources, you can’t install flooring over the top of flooring for this application or use a membrane of any kind, as failure is inevitable. Rarely is looking outside first considered or thought of when installing flooring material.

Q: If in doubt, what resources are available?
If you ever doubt installing anything anywhere-stop. The act of installation constitutes acceptance, making you liable for any failures thereafter regardless of how well you may argue your case. You won’t, at any rate, escape unscathed. Don’t be an island; there are always answers to your questions, and they don’t always come from the manufacturer. You can contact us, and we’ll answer your questions with answers you can trust; it’s what we do.

Copyright 2019 Floor Focus 

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