Recycled buildings

Buildings that were once factories, mills, breweries or warehouses are increasingly being converted to occupied space.

Christopher Capobianco

Sometimes a company expands office space into the warehouse or an old factory is converted into retail, offices or apartments. This is a way of recycling old buildings and the practice is widely known as “adaptive re-use.” Often existing wood or concrete floors that had never been covered before are being covered with a variety of floor coverings.

Proper testing, preparation and planning will prevent poor performance and the results will be something to be proud of.

In the case of concrete slabs, the assumption is often made that an old slab has “cured” or “dried” a long time ago, so there should be no problems as far as moisture is concerned.

Nothing could be further from the truth. Moisture-related failures happen frequently in old buildings when someone assumed moisture testing was not necessary because of the age.

If the slab is on or below grade, meaning in contact with the earth, it may have been designed without a vapor retarder under the slab. The vapour retarder blocks moisture vapor from passing through from the ground through the slab during the process of evaporation. Whether the building is in a desert or right on the water, there is always water in the form of vapour moving from the ground to the sky, and the vapour retarder slows down that process. Of course, if the slab is intended to be left “as is” (such as a warehouse, parking area, a patio or sidewalk), the extra time and cost for sub-slab moisture protection would be necessary. However, if you cover that slab with any type of floor covering, you trap the moisture and the alkalinity that often travels to the surface with it, and all kinds of problems can develop.

In this old building, extensive repairs to the existing concrete were needed. To prepare for floor covering installation, the slab must be treated with a moisture mitigation system first.

So, before starting to work on a space that’s never had a floor covering, ask questions, do moisture tests and prepare for a possible moisture mitigation project. This applies regardless of the type of floor covering being installed. For example, don’t assume that so-called “waterproof” floating LVT or a carpet over pad would be immune to moisture issues. Moisture underneath a floor covering can lead to issues such as mold or bacterial growth, even if the floor covering itself is “waterproof.”

Never forget that the industry standard, ASTM F710 (Preparing Concrete Floors to Receive Resilient Flooring available at is very clear; “Concrete floors to receive resilient flooring shall be tested for moisture regardless of age or grade level,” and this applies to every other type of floor covering too, not just resilient. Second, when in doubt, check with manufacturer for guidelines on what the moisture limits are for patching/leveling compounds, adhesives and floor coverings.

Another potential problem with concrete slabs can be contamination. Existing dirt, paint, sealer, adhesive or residue needs to be cleaned off. Just patching over it is not enough because the patching compound may not adhere to whatever is there; abrasive cleaning such as bead blasting or grinding may be necessary. In severe cases, oil or chemical contamination from some kind of manufacturing or other use of the building in its past can really create complications.

Over old wood subfloors, a careful inspection is the first step before planning the floor installation. Whether the existing floor is a board subfloor or plywood, all loose boards need to be re-nailed into the joists and any damaged or rotted sections must be removed or replaced. If the subfloor is over a crawl space, an inspection needs to be done beneath the floor as well.

Moisture related failures can happen regardless of the age of the building. In this case, adhesive beneath a vinyl plank floor could not tolerate high moisture levels.

A well-ventilated airspace with a vapour retarder over the ground is a must. Without it, moisture has nowhere to go but up, which can affect the entire flooring system, causing swelled underlayment, soft spots, squeaks or worse – rot or mold.

The next step will depend on what the finished floor will be. In the case of resilient flooring, the total thickness of the subfloor and underlayment should be at least 1 in. If the new floor covering is going to be fully adhered, you will almost always need to install new underlayment that is specifically made as a resilient floor underlayment, with a manufacturer’s warranty.

Over a board subfloor where the boards are 3 in. wide or less, 1/4 in. thick plywood is the minimum. For boards wider than that, 3/8 in. or thicker is required. Over old plywood, use a thickness that will get you over the 1 in. minimum.

Christopher Capobianco has been in the floor covering industry since the 1970s in various roles including retail and commercial sales, technical support, consulting, journalism, education and volunteer work. He currently is part of the sales team for Spartan Surfaces in New York City. You can reach him via [email protected].

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