Foundations and basements are not synonymous however we group them as they are most commonly found together in our climate. The foundation wall rests on a footing and acts as the support the home carrying its weight below the frost line. It prevents the house from moving as a result soil movement acting as a retaining wall resisting lateral pressure from the soil. The basement on the other hand is merely the space created by the foundation walls. Other types of foundations include crawl space and slab on grade (monolithic, or, supported on a foundation for example).
The material used for foundation walls include stone, brick, block, concrete, and, wood. Piers, made from similar materials, rest on a footing below the frost line. Pile foundations on the other hand can be made from similar materials, or steel, and are driven into the ground. They are often used when the soil is poor at the upper layers.
Wet Basements — Perhaps one of the most important areas associated with an examination of the foundation include looking for signs of moisture/water penetration and the structure itself. Water penetration through a masonry foundation can ultimately deteriorate the foundation wall reducing its strength allowing movement in the wall itself. Generally, this can be a long and drawn out process.
Removing/reducing surface water by ensuring, proper exterior lot grading, and, that gutters and down spouts work properly and divert water at least 6 feet away from the home for example, may assist with water/moisture problems. Ground water on the other hand may require significant work such as water proofing the basement walls, sump pit and sump pump, drainage tiles, etc. Ensuring that sump pumps are working properly, that sump pits are clean, and, that weeping tiles are free of debris may assist in this regard as well. How do you clean weeping tiles? Sometimes you can clean them by forcing water through them with a power washer if they can gain access.
Many basements are known to have leaked at one time or another during their life span. It usually occurs on an intermittent basis, perhaps after a rain or as snow thaws. It may start soon after a rain or after longer heavier periods. Often water leaks are not a structural concern and can be controlled quite economically.
Cracks In Foundation Walls — are they alive or dead? That is, are they still moving? Movement often determines if there are further structural concerns with the crack as the damage itself is already present. To check for this try placing a vertical line on each side of the crack (see diagram) and measure the distance between the two lines over a period of time. Sometimes these cracks will open and close with the seasons or simply continue to open up/widen.
A crack in the foundation wall, uneven settling, and walls being out of plumb are just a few items which may indicate a problem.
Crawl Spaces — ventilation in crawl spaces is very important. Without proper ventilation damage, structural and/or otherwise, can occur from moisture.
A general rule of thumb is that a minimum of one square foot of venting should be provided for each 500 square feet of the crawl space. At least two vents should be used to maximize airflow. The vents should be located as high as possible to catch naturally occurring breezes. Increased ventilation for crawl spaces with dirt floors is recommended. Insulation and vapour barriers in the crawl space may also be a factor.
Venting of unheated crawl spaces should be provided at all times. This may be in conflict with maximizing the efficiency, and/or the operation, of any heating/cooling equipment contained within the crawl space. Crawlspaces that are heated should have air circulation / cold air returns, insulated walls / floors and appropriate vapour barriers. Vents for these areas should be open in the summer and closed in the winter.
Condensation — sometimes condensation can fool people into thinking they have a leaky basement. This moisture however can be caused by a number of things. Opening basement windows in the summer time is a classic way to get condensation occurring on cold water pipes or your cool foundation walls. How? It’s created when warm humid air meets the cooler basement foundation walls. To check your foundation walls try taping a clear plastic sheet tightly to it. After a couple of days check it and you should be able to see if the moisture is accumulating on the outside or inside of the plastic. If it’s on the outside it’s condensation. If it’s on the inside you may have a leaking foundation wall.
Water/moisture can also promote mould, mildew and fungus growth — all it takes is a warm moist environment. CMHC has information contained within two booklets called “Cleaning Up Your House After a Flood” and “Clean-Up Procedures For Mould In Houses” that are good resources on this topic.
Tip: Keep basement windows and cold cellar vents closed in the summer to reduce condensation and the chance of mildew/mildew growth.