DIY – Polished Concrete flooring over gypsum underlayment

Gypsum cement floor underlayments and radiant floor heating systems are being specified in multi-level condominiums, hotels and high-rise buildings in conjunction with stained concrete flooring or polished concrete flooring. Past technology did not allow concrete overlays or micro-toppings to be installed directly to the surface of a gypsum substrate. Duraamen’s concrete micro topping has been successfully installed over gypsum based underlayments. Once the gypsum based sub-floor is properly installed and cured in accordance with the manufacturer’s directions, preparation for the installation of concrete overlay may begin.

Recently, Ms. Kelly who resides in Palmer, Alaska completed a stained concrete flooring installation over gypsum sub-floor. Kelly is a DIY enthusiast who has a done a commendable job in following instructions but also showing creativity with the use of Aquacolors (water based stains) over concrete overlay or micro-topping. The following steps are recommended in the installation of Skraffino micro topping –

1. The underlayment must be sufficiently dry and properly cured to manufacturer’s specifications for permanent, non-moisture permeable coverings.
2. If the gypsum underlayment is installed over wood or plywood subfloor, the deflection shall not exceed 1/360th of the span. The surface shall be dry and free of all grease, oil, dirt, dust, curing compounds, waxes, sealers, efflorescence, old adhesive, gypsum-based patching compounds and any other foreign matter.
3. Apply at least two coats of acrylic coplolymer based primer, Cp1000 allowing at least 6-8 hours between the coats. If the substrate is porous more than two coats may be required. A rule of thumb is to see a nice uniform sheen which indicates sufficient priming.
4. Apply Skraffino, concrete overlay as per the technical data sheet. A minimum of two coats are necessary.
5. After Skraffino is cured for 18-24 hours, it is ready to accept water based stains or even chemical stains (acid stains).
6. After allowing the concrete stains to dry for at least 24 hours (may be more or less depending upon the ambient temperature), the surface is sealed with acrylic, epoxy or polyurethane topcoats.

For residential applications two coats of water based acrylic sealer are sufficient. However, for residents having pets or young children we recommend epoxy and polyurethane sealers. Kelly used one coat of water based epoxy primer/sealer, Perdure E32 and one coat of water based aliphatic polyurethane, Perdure U46 for low maintenance.