Wet basements and settling foundations are a common problem in the Ottawa area. Whether it’s a poured concrete, block or stone foundation, there’s a good chance you have experienced moisture or water issues in your basement.
There are several ways to waterproof a foundation. While every home is different due to soil types and drainage systems, there are a few common ways water enters a foundation. This simplified diagram below demonstrates how humidity and water can enter a basement:
1) Water entering from above the footing.
2) Water entering under the footing then seeping through the floor slab.
3) Moisture can find its way through cracks in the floor, especially if the slab is poured directly on soil (slabs should be poured on a proper base with drainage using 4-6″ of clear stone).
4) Basement windows must have a 6″ minimum clearance from the exterior grade, otherwise windows should not be installed.
5) Water can find its way around pipes that are penetrating the foundation walls (such as a/c units, hydro or water lines, etc.).
6) If grading around your foundation is too high, water can seep over the sill plate.
7) Damaged mortar joints or wall fractures are common causes of humid and wet basements.
8) Defective or under-sized sump pump.
9) Damp air from humidity or condensation.
10) Walk out basement stairs.
There are three main types of waterproofing solutions, depending on your needs. They are described below.
A fracture found in a foundation can be sealed with an epoxy or polyurethane injection if the foundation is done settling, the crack is relatively narrow and it is a poured concrete foundation. Epoxy injection is a simple method that offers a quick and easy solution. However, the cause of the crack should always be investigated to ensure the integrity of the structure is not compromised. If the crack appears in the first year after construction, it is most likely due to the concrete shrinking and settling, but if it’s getting larger over time then it could be a serious matter. If a whole section of foundation is settling, you may need to carry out underpinning of the foundation. Not all cracks can be permanently sealed with injections, but it is an inexpensive first step.
Interior Water Control System
Interior water control systems are practical in situations when excavating from the exterior is not an option. Obstacles such as interlocking brick or pavers, blockage by structures, insufficient room for machinery, and even soil containing too many rocks can get in the way of an excavation. What’s most appealing about this interior method is that you can waterproof from the inside while your exterior stays intact and save money on the overall project.
Adding a weeping tile is one step in the process of interior waterproofing. Weeping tiles are also used when underpinning a foundation. They are added along the perimeter of a new grade when your new floor height is a lower grade than your existing footing.
If you are already in the process of underpinning your foundation, it is likely that your new floor height would be a lower grade than your existing footing, which will require a weeping tile running along the perimeter of your new grade. At this point, it’s a great time to go the extra step and waterproof your interior foundation walls since half the work is already done (weeping tile).
First things first: ensure your foundation is structurally sound. If you’re working with a block or especially a stone foundation, you will most likely need to do some repointing. If you’re working with a poured foundation, fix the cracks if there are any. Once your foundation is structurally sound, the next step it to install the drainage board. Your drainage board doesn’t necessary need to go right up to the ceiling, as long as you’re above the exterior grade. And it should run down to your weeping tile. Termination strips should be installed along the top of the drainage board and be fastened with concrete nails. Once fastened, the top of the termination strip should be sealed with caulking. Any edges or overlaps of the drainage board should also be finished with termination strips.
The next important part of this system is the weeping tile. First and foremost, ensure that it’s entirely embedded in clear stone, and running along any exterior wall you want to waterproof. It also needs to be slightly leveled towards your discharge point which, in most cases, is a sump pit. A very, very small slope is sufficient; some engineers are even satisfied with no slope, as long as it doesn’t slope the opposite way. Also make sure that there are no inclines anywhere, or any sort of “bump”. All of this is done prior to the installation of the basement floor slab. So in theory, once the weeping tile is installed, the entire basement floor area should have 4” of crushed stone, ready for your slab to be poured. You should test your system by flooding the area near your weeping tile. You should slowly start seeing water draining into the sump pit. If that’s the case, chances are that everything is done correctly. Don’t be surprised if you see only small amounts of water, as it will take a good deal of water to fill the entire weeping tile enough to overflow into the sump pit.
This is a great alternative for waterproofing your foundation. It can be a cost effective option, especially if done at the same time as an underpinning.
A commonly known method is undertaken from the exterior by adding membranes and drainage to the foundation. Below are pictures of recent exterior projects showing all three foundation wall membranes with a good 24″ base layer of clear stone covering the weeping tile. The layer of clear stone gets covered with a geotextile fabric to prevent soil from clogging up the drainage tile. Even though the weeping tile already has a filter fabric, it is also important protect the clear stone.
Some of these repair methods can be costly. However it's not rocket science and with a little research and elbow grease, it can be a DIY project.