How To Prepare For Moisture Prevention Before Sealing Your Concrete Basement Floor

Posted on: 30 May 2017

A damp concrete floor can provide a perfect environment for mold and mildew, along with the possible allergic reactions and foul odors that accompany them. The first actions you need to take is to eliminate, or at least reduce, possible sources of moisture. You can then apply sealant to the floor to both keep moisture away from staining the unfinished concrete and also to keep moisture from leeching from the floor itself.

What are the possible sources of moisture in your basement?

Overflow from downspouts

If your downspouts are clogged or blocked at ground level, water can accumulate around the foundation of the home and eventually find its way into the basement. Clean leaves and other debris that may have been washed down the spout and solidified into a solid mass that blocks or redirects the flow of wastewater from the home. You may also need to re-position the downspout and the bracket that secures it to the wall if they have been pushed out of place by bad weather or an accidental bump.

Warm air entering the basement

Warm, humid air will produce condensation when it enters a cooler basement, so sealing around any possible apertures such as pipe abutments is crucial for keeping moisture out. Expanding foam insulation will provide the necessary protection, but use it sparingly, because it expands several times its size when applied.

Cracks in basement walls or floor

Concrete sealer should be applied to fill in all cracks in the walls or floor and allow to cure according to the manufacturer's specifications. Additional time may be required if the walls or floor crevices are damp,but this can be ameliorated by the use of fans or a dehumidifier both before and after application of the crack sealer.

Applying a floor sealant

Although you can move all of the items in the room to one side and seal the basement floor in two parts, it's must simpler to remove all of the items from the room. If there is molding along the perimeters of the floor, it should be removed with a pry bar before cleaning has begun, because there is likely to be a lot of dirt, dust, and dead bugs behind the molding.

The floor must be cleaned and vacuumed thoroughly to allow proper adherence of the sealant. If you mop the floor to remove any remaining contaminants, it must be thoroughly dried before applying the sealant.

What type of sealant should you use?

You should use a water based sealant for interior concrete sealing, because solvent based sealants are hazardous to breathe as well as extremely flammable. Your choices range from the least expensive acrylic sealants, which form a thin coating over the concrete that is more easily worn away than other types of sealants, to more expensive polyurethanes and epoxies, which provide a more durable surface and a brighter sheen.

Acrylic sealants may actually be preferable in homes with concrete floors that leech moisture from improper curing when the concrete was originally poured, because acrylics are more permeable than some other sealants, allowing moisture to be released from the concrete instead of being trapped below the sealant layer.

You may also choose a sealant that helps to block radon gas from entering your home through the pores of your concrete floor. It is an odorless, invisible gas that is formed by the breakdown of uranium in the soil under your home, and is a leading cause of lung cancer. These sealants also penetrate deeper into the concrete to provide additional protection against moisture.

However, if radon blocking is your primary motivation for choosing a sealant, your home should first be tested for high levels of radon before choosing this option, because you are spending additional money with little return on your investment if the radon levels are low in your home.