AVOIDING WET BASEMENTS – Part 3 – Drainage under your homes concrete floor

Draining under your homes concrete floor

Wet basement floors are common in this part of the country and most contractors will tell you every home should have a sump pump. I have a different opinion as I see hundreds of dry basements that have been designed correctly and are therefore dry and they don’t have a sump pump. I hear the phrase often, “well it couldn’t hurt could it?” well in fact I believe it might, here’s why. If you jack hammer into a perfectly good basement floor you are now exposing the home to whatever might be under that floor. I have been in homes where you can hear the weeping tile running but the home has never had a leak in its 35 year history. If you disturb this process you may be opening up a can of worms you don’t want to deal with. I always say don’t fix it if it is not broke! By opening up the floor you are now directing the flow of water to the sump and relying on a pump to do what other systems have successfully done for decades. If and when your sump pump fails you now have a problem. I always look at the history of the home to tell me if changes are required.

On the opposite side of the coin you may live in a damp basement that has little or no water control systems. As a result your basement floor might have significant amounts of efflorescence (white powder) on it and you are experiencing a musty smell. Obviously something must be done and a sump pump is an obvious solution, or is it? I have experienced many damp basements that have a dry sump. The problem is this, the water under the basement floor is not free to travel to the sump. Instead of migrating under the floor to the sump pit, the water simply pushes up under the slab.

Many of the early basements models were missing two critical components that we use today, a thick layer of crushed rock and vapour barrier. The problem with most basements from the 70’s and prior, is that they did not provide a pathway for water to travel under the slab without touching the bottom of the concrete floor. Even if gravel was used, it was often pushed into the clay and became ineffective as a drainage plane. When the water table is high as it has been in recent years, the ground under the concrete floor becomes saturated. This excessive moisture often looks for the path of least resistance and that is usually up through the unprotected concrete of your basement floor. Today we add a layer of vapour barrier and 6-12 Inches of clean crushed rock that provides a pathway to the drainage system for the water rather than just letting it sit under the floor.

Adding a sump pump in an older home may help alleviate some of the water issues but don’t count on one sump in the corner or anywhere for that matter, solving your water problem. As I mentioned above, the water will take the path of least resistance and that is often up through the floor rather than across the basement to a sump. When I see this type of home and problem I will always look to the outside to see if there are any means of controlling the surface water to reduce the load on the basement. Often the slope needs correcting and the downspouts can be better arranged. If your home is built in a hole at the edge of a swamp you may have issues that require extensive repairs at a high cost. For most city dwellers however, the answer may lie in the exterior grade and water control systems. In a worst case scenario jack hammering out the floor may be necessary in order to get control of the water issues under it. As always feel free to contact me for free advice. If you require a home visit I charge $150 for a comprehensive assessment of single component systems.

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