Winnipeg Free Press - PRINT EDITION
ASK THE INSPECTOR: Brick foundations pose repair challenges
QUESTION: In a previous column for the Winnipeg Free Press you gave some advice on repairs to leaks for non-stone foundations. In that article you wrote that epoxy injection is not an option for stone foundations.
What options or advice would you recommend for a brick foundation built in 1925? Marg Friesen
ANSWER: The advice I would give to anyone living in a home that was almost 100 years old in our area with a brick foundation would be to move or sell. While I am obviously kidding, this advice is not far off the mark, unless you live outside the Red River Valley where soil conditions may be more favourable to brick foundations. Certain types of repairs to some foundations are not practical. For the same reasons, some types of materials used for foundations in the past may not be worth repairing. Clay brick foundations fall into this category. There are two main reasons why this is the case: structural problems and moisture.
The main problem with brick foundations in our area is the inability to withstand the tremendous forces they face from our expansive clay soil.
Because brick walls are constructed from layer upon layer of small individual units held together with mortar, they have a tendency to have very limited flexibility and lateral strength.
Over time, the forces of the soil outside the foundation will cause the walls to bow inward as the mortar ages and wears.
While this should not initially compromise the vertical strength of the foundation, further deterioration may lead to serious movement in the home. While it may be possible to do repairs similar to other foundation types, by exterior excavation, reapplication of damp-proofing and bracing the interior, complete replacement with new concrete walls may be the only solution in the worst cases. Even in moderately damaged foundations, the second property of brick walls may make standard repairs prohibitive.
Clay bricks are porous and absorb moisture. While this may be a good property for an exterior product used for siding, it is not desirable for any material to be used below grade. Even with a heavy application of a bitumen-based damp-proofing material, clay bricks eventually deteriorate due to ground moisture. As the waterproofing layer and mortar joints wear out, and the foundation walls allow moisture to penetrate the clay bricks, deterioration can accelerate.
Even if the walls are several courses thick, deterioration to the outside course will compromise the strength of the inner layers. This will allow more water to penetrate the foundation during heavy precipitation, creating more inward movement, more mortar damage, and an escalating cycle of deterioration.
The only way a brick foundation on a home your age can be repaired is if you live in an area with highly sandy soil conditions. If the soil is quite sandy, rather than clay-based, then lateral pressure may not be a major consideration.
Also, sandy soils drain much better than other types, minimizing the amount of moisture that can be forced into the bricks from hydrostatic pressure. If that is indeed the case in your home, I could see how this type of foundation has survived for almost a century without collapse. In that situation, any possible repairs would only be attempted from the exterior.
Excavation outside your foundation will be the only practical way to not only prevent leakage and further deterioration, but also assess the condition of the brick walls. Even with sandy soil conditions, there may be considerable deterioration to the bricks hidden below grade. Digging down in a few test areas, where seepage is the worst, may give a rough idea of the current state of the foundation. If there is no serious damage to the surface of the exterior course of bricks, and minimal inward bowing, typical repairs may be possible.
Remove all dirt, debris and loose mortar before repairs begin. After this is done, fill all worn mortar joints, followed by a complete parging coat of mortar over the entire foundation.
If a limited number of bricks are badly damaged, loose, or missing, these can be replaced prior to the parging coat.
Once that is completed and the mortar has cured, covering the foundation with a waterproofing membrane is the next step. Use of a more modern membrane system, such as a blueskin or semi-rigid dimpled sheathing should be superior to a simple bitumen coating.
Following the membrane installation with a thin layer of rigid foam insulation will give added cushion and protection to the brick walls. Replacement of a plugged weeping tile system, if one was even installed, with modern corrugated plastic drainage piping will be the final piece of the repair puzzle.
Because of the nature of brick foundations, simple, inexpensive repairs are not normally possible to stop seepage and movement issues.
Depending on the soil conditions, repairs may vary from exterior excavation and repairs detailed above, to complete removal and replacement with modern reinforced concrete foundation walls.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the president of the Canadian Association of Home & Property Inspectors - Manitoba (www.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 www.trainedeye.ca.
Republished from the Winnipeg Free Press print edition August 3, 2013 F10
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