In keeping with our do-it-yourself motto of “you’ve got to try it at least once” today we’re going to be parging our foundation.
After a home’s foundation has been poured, and the plywood forms removed, the homeowner is left with an exposed concrete wall that isn’t so attractive. In order to remedy this situation, since there’s often 30-36 inches of exposed wall between the grass and the siding, the contractor will apply a thin coat of a cement product called pargemix.
The same situation exists with today’s foam foundations. Whatever portion of foam that isn’t covered by siding, will need to be sealed with a parging compound.
Because all homes settle a bit over time, this thin coat of concrete can develop a few hairline cracks. As water and moisture enter these cracks, thereby infiltrating this cement layer, the parging will tend to break off in small chunks over time, once again exposing the foundation’s rough surface.
The good thing about the task of parging is that it’s a non-structural operation. Parging is essentially a decorative, or esthetic feature. So, if the parge mix happens to fall off in a month or two, or your habit of creating cupcakes with lopsided frosting tops somehow transfers to a foundation wall that is somewhat less than perfectly smooth and level, only your pride and status as a true do-it-yourselfer will be hurt.
However decorative, parging is still the first line of defence against water penetrating the foundation. So, and regardless of the fact a foundation simply looks better after it’s been parged, parging does serve a purpose.
When parging a concrete foundation wall, first tap off or chip away any loose pieces of existing cement with a small hammer and concrete chisel, then sweep things clean using a steel brush. Other tools for the job will include a clean 20L. pail, 24” drywall mixer, 4”x12” cement trowel, 4”x9” sponge rubber float, a notched trowel, margin or pointing trowel, and a tin can or similar type container for scooping.
The drywall mixer attaches to any standard drill, and is essentially a giant beater blade that will blend your pargemix compound in the same manner a power mixer stirs up a cake mix. Besides saving you time and energy, the mixer is key to avoiding further wear and tear on those achy shoulder and elbow joints.
Once the concrete surface has been brushed clean, rinse the area to be covered with your garden hose. Next, pour four litres of water into your pail, then slowly scoop the 30 kg bag of pargemix into the pail, while at the same time operating your drywall mixer. To increase the sticking power of your pargemix, you can replace one litre of water with a one litre bottle of “All-Crete”, a concrete adhesive designed especially to encourage new concrete to stick to old.
Mix the pargemix/water solution for about five minutes. With the pargemix at a nice, spreading consistency (add more water if it’s too thick) use your smaller margin or pointing trowel to gather up a load of pargemix out of the pail, then place this mass on your 4”x12” cement trowel, then apply it to the wall. Start at the bottom (grass level) spreading the pargemix onto the wall as you move your trowel vertically upwards. Perform a few more vertical strips, then work your trowel horizontally to spread things out. A dampened sponge trowel will further help smoothen the parging compound.
Pargemix should be applied no more than half an inch thick. If your foundation wall is severely pitted, you can apply a thin coat on day one, then a second layer a day later. If a second layer is in the plan, etch your first layer with a notched trowel before it dries. This will give the second layer something to grab onto.
If you’re parging a foam foundation, prepare the surface by fastening diamond lath to the foam blocks using deck screws and foam washers.