Renovation & Design

Leaky foundations best fixed from outside

May not be necessary for minor seepage

Today we have two questions I have selected from the many I regularly get on everyone's favourite topic, especially this time of year, basement seepage.

I read your column on a regular basis, and I was hoping you'd be able to help me with my problem. My home was built in 1962, and has cement walls in the basement that are experiencing leaks in a few areas where the original wire ties stick out of the cement wall. I'm in the process of opening up all the walls in the basement to renovate, and wanted to check if there is anything I can do to repair the areas affected and also deal with the ones that don't currently leak from inside the home.

Thanks very much for your help.


--Roger Bouchard, e-mail

I experience occasional moisture in the basement, precisely along the joint between wall and the floor. I noticed the problem only along one wall, but it might be along other walls as well. I took the drywall and insulation down on the problem wall and it confirmed that there are no cracks on the wall and the problem is located within 20 to 30 centimetres of the floor. Also worth mentioning, the eaves were clogged for some time and last spring it was raining a lot. We are just doing roof and eaves replacement which will fix that problem, but I feel that still something needs to be done with the walls. The floor, which has a crack, has some moisture coming through it as well. My options are to do excavation from the outside and fix it by replacing the weeping tiles or an internal repair by removing part of the floor next to the wall, digging a trench beside the footing, and embedding weeping tile there directed to the sump pit.

Which one will solve the problem better?

--Mario Paskvalin, e-mail

Answer -- One of the most difficult problems to diagnose in homes is the exact location of moisture intrusion, especially in basements with partially finished walls. I am glad to see that both or you have decided to remove the wall coverings from the foundation areas in question before proceeding with any foundation repairs, which may be quite costly. Visual access to the inside of the concrete foundations is critical to pinpoint the areas of leakage and decide upon proper repairs.

As stated in the second inquiry, you have not seen any visible cracks that would account for the water leakage. Logically, you have then surmised that the water must be coming through the crack between the floor slab and the foundation wall but you may not be correct. Your description of the evidence of moisture being visible only at the bottom of the foundation may have other causes. As in Mr. Bouchard's home, you may have one or more rusted form ties that have disintegrated, leaving small holes in the foundation wall. The older snap ties, as they are also called, are typically installed in fairly straight rows along the length of the foundation wall. They often will rust and leak one after the other, forming a fairly regular pattern of moisture on the walls. Look for water stains, rust stains and efflourescence underneath these small holes, which may give some indication of the problem area.

Another very common factor in basement leakage, which is more typical with the leakage patterns you are seeing, is deterioration of the damp-proofing on the exterior of the foundation. This thin bitumen or asphalt- based coating will often wear out after several decades, allowing the concrete to absorb moisture from the surrounding soil. If this moisture exceeds the retention capabilities of the concrete, moisture will seep through, often detected first by flaking or spalling surface concrete on the inside. If this is evident on your foundation, after removal of wall coverings and insulation, it is just as likely a culprit as the crack at the floor slab edge. The interesting thing is that the most successful repair method for both causes of leakage is the same, which I will address later on.

As for patching the leaking form ties seen in the first question, this may depend on the extent of the leakage and deterioration of the small, metal wires inside the foundation wall. If there is only minor seepage or drip stains, patching the inside of these indentations with hydraulic cement may help, considerably. This patching material should be installed after chipping or grinding off the rusted metal and any loose concrete. If the seepage is more extensive and a visible hole is seen where the rusted wire used to be, then further repairs may be required. Often, these holes can be plugged by injecting epoxy from the interior of the foundation. If properly installed, the epoxy, along with improved grading water management outside the foundation, should provide a fairly permanent repair.

If the deterioration on the interior of the foundation is more extensive, the area around several form ties excessively worn, or several cracks seen that have evidence of leakage, exterior repairs may be required. Most exterior excavation repairs will include patching cracks and openings in the concrete, reinstallation of the damp proofing on the exterior and at the joint with the footing, and replacement of older, blocked weeping tile with modern plastic drainage piping. To answer both of your questions, this will be the best method for repairs of a leaking foundation, but may not be necessary if there is only minor seepage through a couple of rusted ties or small cracks. Internal weeping tile installation is not a good solution, in my opinion, as the messy and costly installation may affect the structural integrity of the basement floor slab and does nothing to stop further deterioration of the outside of the 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 ( Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, #110-2025 Corydon Ave., Winnipeg, MB. R3P 2G9. Ari can be reached at (204) 291-5358 or check out his website at .


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