We are new to Winnipeg, trading in the wild, west coast with its rain for the sunny, snowy climes.
This winter we have experienced a couple of noticeable cracks in two walls. One is in our great room, which is an addition, and one over the doors of one of our en-suit off the bedroom. The bedroom door has gotten tighter also. This, in the midst of renovations where the basement has been finished, under the bathroom and bedroom, but none near the great room. We did have a sump pump put in and the foundation was opened in the new area for plumbing work. Otherwise, we don’t see what might be causing any movement except for the snow load. The bungalow has a low-pitched roof, was initially well built in ’72 with the great room added in the late 80’s onto the back wall of the kitchen. We are currently finishing the basement and retrofitting the kitchen.
Any help in thinking through this problem will allow us to proceed in fixing it.
Being new to our fine city, you may not be aware that homes in this area are prone to a large amount of settlement due to our clay soil. This is particularly noticeable with the change in seasons, due to frost heaving and changes in moisture levels in the expansive soil. This is likely the reason for the newly visible cracks, which may not be new, but are opening up after repeated patching and painting.
Foundation movement, or settlement at it often referred to, results from expansion or shrinking of the clay soil with changes in moisture content. Often the soil will expand in the spring due to snowmelt, frost expansion, and spring rains and will dry out toward the end of summer and fall. This can cause the footings that support the foundation walls and beams in your home to move up or down, somewhat. There may also be considerably more movement in the footings beneath the concrete basement slab than those below the perimeter foundation walls. This can cause bumps in the floor as well as the cracking and stickiness in the interior doors you are observing. Because of the age of your home, you should have adjustable steel teleposts sitting above these interior footings and minor adjustments may be required to minimize this movement.
The only thing that may have affected your home in the recent renovations is the addition of the sump pit and pump. Depending on how this is installed and how much it has operated since installation, it can have a significant effect on the interior movement. If this newly installed system is collecting considerable amounts of groundwater, that used to remain in the soil under the basement floor slab, and pumping it outside it may cause the soil beneath the floor to dry excessively. This is not normally a concern, but your home may have become accustomed to this high moisture content in the soil in this area and a sudden change may cause movement in the footings. Again, telepost adjustment may be the answer if this is the case.
None of what I have stated so far is unusual or overly concerning for a home your age, but if the cracks are not as I perceive them, there may be a larger problem at work here. Often additions will have differential settlement to the original structure that they are built on to. By this I mean that the addition may settle at a different rate than the original home or more likely, stay put while the original house continues to move. This is because most properly built additions in Winnipeg have poured concrete piers installed to support their grade beam foundation walls. This will make the addition foundation much less prone to settlement than the original one.
It is very common to see exterior cracks in the walls where an addition meets the original structure due to the aforementioned reason. Unfortunately, these cracks may also appear in the drywall of the interior walls. If the cracks open up to a large enough size that water or pests may be able to infiltrate the wall cavity or home, then repairs may be required. In this case, installation of expansion joints or other modifications may be required to prevent further damage. I would certainly undertake these repairs, if needed, before continuing with the kitchen renovations.
If the cracks are diagonal or horizontal in direction and more than hairline, further evaluation may be required. A visual inspection by a CAHPI Home Inspector or a Licensed Structural Engineer may be in order. The inspector should be able to determine whether repair or remediation is required or if the cracks are just cosmetic in nature. If the cracks are deemed to be serious, a Structural Engineer should be able to provide a detailed plan of remediation.