The Importance of Waterproofing Your Concrete Foundation for Winter


Most people understand the necessity of having a structurally sound and damp-proof basement foundation.

What many people don’t immediately recognize, are the signs which signal the need for proper concrete foundation waterproofing. This can result because of finished interior basement walls, or simply the fact that many people don’t spend a great deal of time in an unfinished basement environment.

As a result; it becomes a good idea to incorporate into one’s regimen of maintenance inspection; checking the basement floor, interior basement walls, exterior foundation walls, and associated downpipes, which exit into the in-ground drains near, or at foundation walls.

In some areas of Toronto, homes are located in very close proximity to one another or are virtually touching one another. Such design configurations can be difficult to inspect, and even more difficult to perform concrete foundation waterproofing.

Under such circumstances, it can be possible to waterproof from the inside of the building. For most homeowners with conventional construction homes, exterior waterproofing is the desired course of action.

Enlisting the services of a professional masonry and waterproofing contractor is the best course of action, to receive an accurate appraisal of the scope of work necessary to correct any such concrete foundation deficiencies.

Signs that you require waterproofing assistance include; the appearance of efflorescence (white chalky marks on interior concrete basement walls), visible internal cracks, damp or wet areas visible on basement walls or wall to floor junctions, dampness or musty smells, or evidence of mould on finished basement wall surfaces.

What is required to complete comprehensive concrete foundation waterproofing?


The first step is to determine how extensive an area requires waterproofing. It is often possible to do one side of a home if the budget is a consideration, and carry on with other perimeter sides when a homeowner’s budget would permit. This approach assumes that there is no visible evidence of leaks found on adjacent foundation walls.

If undergoing a strategic concrete foundation waterproofing repair; it is advised to go from one exterior corner to another as a minimum, and to wrap around the opposing corners, even if only one or two feet.

Most typically; concrete foundations are more vulnerable to leaks after twenty years, but some newer construction builds have exhibited problems in less than ten years if the workmanship has not been of the best initial quality.

Other common sources of leaks around concrete foundations can be traced to sumped, basement window wells, and in-ground drains which have become corroded over time. Many older homes have clay tile pipes below grade as an example; which can break down over decades.

It is also important to maintain grading away from the foundation, so that groundwater has a path to shed away from the home’s concrete foundation. Cracks and shifts in the structure of the concrete foundation are obvious vulnerable points for water ingress. Such repairs can be made using hydraulic cement, and or injecting epoxy if the cracks are small enough.

In severe circumstances where concrete block foundations have shifted over time; strategic concrete block replacement may form part of the remedial strategy before actual waterproofing can begin.

Excavation of a trench around the specified concrete foundation wall must be completed to reach the footings of the foundation. Part of the excavation can include carefully removing finished hard surfaces such as poured concrete walkways or interlock paver walkways. The easiest excavation involves the removal of sod and related earth.

Also to be considered in this step of construction is where removed materials can be placed. If there is only three feet between houses; materials have to be transported and located temporarily elsewhere.

Under such circumstances; one must also consider the integrity of a neighbour’s foundation located in close relationship to the one being worked on. Many neighbours will consider completing their respective sides in tandem; which can serve to help both parties reduce some costs associated with excavation.

It is important for a neighbour undergoing such work to be cautious that the adjacent neighbour does not assign blame for concrete foundation leaks that they may have, as a pre-existing condition. And particularly after their own waterproofing has been completed. Therefore; it is advised to extend the courtesy to one’s neighbour by a), advising them well in advance that such work may be undertaken, and b), that they may wish to have their basement /concrete foundation, pre-inspected to identify any issues for which they may take advantage of better pricing, or to exonerate the professional contractor doing such work, and minimizing any potential blame for themselves from that neighbour in the future.

Excavation work is often accomplished using machinery, but in some instances requires hand digging. Soils such as clay can be slow and difficult to extricate. Once the excavation is complete; the next step involves wire brushing and or power washing the exterior concrete foundation surface. This reveals cracks, or structural deficiencies that need attention, and permits a clean wall surface for eventual application of waterproofing materials.

Once strategic structural repairs (if required), are completed; the actual waterproofing may begin.

It is often best to apply a new parged coating of concrete over the existing concrete wall surface. This is particularly suggested if the wall is constructed of concrete blocks. A bonding agent is used to provide for proper adhesion. This must-have time to cure properly. This process is not always required, but under some circumstances can be a must-do step.

A bituminous liquid coating, specifically designed for concrete foundation waterproofing, is then liberally applied. It is most often trowel-applied, but can also be spray applied in multiple coats until the desired thickness of the coating is achieved. A polyethylene barrier is then applied to the wall surface, and recoating of the wall takes place. The waterproofing should extend above the finished grade.

The next process involves the application of a dimpled plastic membrane which acts as a secondary waterproofing barrier and protects the coating beneath. This product is mechanically attached and extends downward to the level of the foundation footing.

At the base of the foundation, a new weeper (plastic corrugated drainage pipe) is installed in an initial bed of aggregate to facilitate drainage. The weeper pipe is covered in a filter sock, which helps prevent debris from entering the pipe and creating future clogs. The characteristic of the weeper pipe is that it has small perforations that allow accumulated groundwater to escape into the surrounding aggregate materials. The weeper is adjoined to an adjacent pipe on connecting foundation sections or terminated away from the foundation under particular circumstances.

An additional volume of aggregate is then applied over the weeper and further compacted to six inches. Previously removed soil can then be restored into the trench and should be re-compacted. Often there is a need for new earth to be added to allow for the result of compaction, and to permit proper grading away from the concrete foundation wall.

Where possible; downpipes exiting from the gutters should be re-directed away from a home’s foundation by at least five feet where possible. Older in-ground drains designed for downpipes should be capped off. Another option for the drainage of roof-related water,  can include rain barrels and or pop up diverters embedded in one’s lawn, well away from the home’s foundation.

As foundation leaks are typically at their worst during winter melt periods, spring runoffs, and prolonged periods of rainfall, it is best to schedule such work in advance of the winter season before the ground becomes frozen.

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