Exterior repairs the way to solve moisture

Hey there, time traveller!
This article was published 30/06/2017 (3090 days ago), so information in it may no longer be current.

Question: I purchased a house a year and a half ago and discovered a large section of one wall of my poured concrete foundation (behind the furnace) where the paint and cement are deteriorating. I’m certain moisture is coming through the concrete and had a contractor come to give me an estimate on weeping tiles. The price is way out of my budget and I was wondering if there was some other way I might be able to dry out the cement or repair the problem? You had mentioned something in a 2012 article about a local entrepreneur that may have come up with an innovative way to solve this problem. Any information would be greatly appreciated.

Thanks so much.

— Tammy Cheguis

Answer: There may be several options for repairing wet or leaking concrete foundation walls, but the only proper way is from the outside. Other, less costly options may help manage the moisture, but will do nothing to prevent further deterioration to the concrete, itself. For that reason, I always recommend exterior repairs whenever possible.

There are several likely factors that may be contributing to your damp, spalling foundation wall. These may range from plugged or damaged weeping tile, deteriorated damp proofing, rusted and leaking form ties, cracks, and poor water management on the outside of your home. The only two of these issues that may be repairable from the inside of your basement are the form ties and some type of cracks. Improving exterior grading around the home, and diverting downspouts further from the foundation, may also be within your power to easily accomplish and help prevent wet walls.

If you have visible foundation cracks, even hairline vertical ones under basement windows, these may be responsible for some moisture intrusion from the soil outside the house. Also, small round metal pieces embedded in the concrete, referred to as form ties or snap ties, may also leak if excessively corroded. Both of these issues may allow a small passageway for moisture from the exterior of the concrete wall to the interior. These areas, if not covered, are often readily visible due to rust stains, efflorescence, or flaking paint and surface concrete around or below the area. If you see any of these specific indicators, there may be one internal option for repair.

Injecting small holes or cracks in concrete foundation walls is a possible way of preventing seepage or leakage during heavy rains or snow melt. This is most commonly done with epoxy, but can also be done with other compounds that are more flexible. Because epoxy is even stronger than the surrounding concrete, once cured, it may also help to strengthen the foundation walls, bonding it together on either side of the cracks. This material can be injected under pressure from the inside, after drilling small access holes in the damaged areas. The other major benefit of this type of repair is that the injected material should completely fill the openings in the foundation wall, preventing further expansion and contraction of these gaps due to the freeze/thaw cycle.

Other interior systems, such as the one you mentioned from a previous column, are normally restricted to situations where there is little possible way to access the exterior of the foundation. They may also be used as a preventative measure for new foundations, to prevent mould growth due to condensation. These systems may help dry wet concrete, but will primarily be collecting moisture after it has already passed through the wall. Because of this, the moisture can still remain in the concrete and small openings, allowing further freeze/thaw cycles to continue expansion and contraction of that moisture. They will do little to prevent further deterioration of the concrete itself, which can lead to future structural concerns, not just moisture issues.

For that reason, exterior foundation repairs are always a better choice. While the cost will be higher, due to the increased labour involved, it is a much better investment for the future of the home. The benefits of exterior repairs are primarily that the moisture can be completely prevented from entering the foundation walls, rather than managing it after it has seeped into the concrete. This can be done with replacement of non-functioning weeping tiles with modern, plastic ones, that should work well for decades. That will remove excessive moisture from the soil surrounding your home. Next, higher quality waterproofing membranes can be adhered to the foundation wall, further preventing moisture intrusion through hydrostatic pressure from the soil. Finally, the expansive clay soil surrounding the home, which may be responsible for the foundation cracks, can be replaced with granular fill that will prevent excessive soil pressure on the walls.

Exterior foundation repairs may be the most costly type, due to the need to remove the soil for approximately one metre outside the complete foundation wall being fixed. This will allow access, right down to the footing, for proper repairs and weeping tile installation. While this may not appear to be within your budget, spending money on any interior repairs may be a temporary solution, at best, and often a waste of resources that could be applied to a better exterior foundation repair.

Just because you have a minor moisture issue in an exposed foundation wall, including peeling paint and flaking concrete, that does not mean you can do a minor repair. If this issue continues, or worsens, proper remediation will require exterior excavation to access the outside of the wall for a proper weeping tile replacement, damp proofing upgrades, and soil replacement, to ensure you have a long-lasting, dry foundation.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.

trainedeye@iname.com