Last Updated: , Created: Saturday, December 30th, 2000

Gumbo Clay and what it does to your house.

For those of you who have move into the area spreading roughly from Winnipeg to Regina, but you have not grown up in this area, the living nature of the soil itself may surprise you. Clay soil under and around a house can cause problems anywhere in Canada, but in this region there is a special clay commonly called Gumbo Clay. It's main characteristic is that it will expand a lot with moisture and shrink a lot when dry and keep on doing that cycle for ever and ever. Hence, houses built on and in Gumbo Clay never seem to finish their problems of settling.  

Yes it is true what the locals will tell you that in a dry fall you must water your house before winter, that is water the soil immediately around the house. If you do not you will discover that the soil pulls away from the foundation, often leaving a gap an inch or two wide open between the soil and the foundation. That not only let's heat out and cold in, but if you were to drop anything, especially rocks into this gap, in the spring the soil will push back against the foundation and possibly force that rock right into the concrete, cracking the wall. So you should never fill in that gap, you should water the soil before it freezes so that it hugs the foundation itself.

If you have this same Gumbo clay under the house, and if the water table changes its level, as is often the case, then you can expect the floor as well as the teleposts in the middle of the house to move up part of the year, down part of the year, and they just keep on doing that season after season. You will first see this with sticking doors in the middle of the house. This tends to present less of a problem for the foundation wall and the outer doors and windows because this part of the house is very heavy and tends to stay put. The middle of the house is not so heavy and moves more easily with the gumbo clay. The best solution I ever saw for this was to string a long copper wire the full length of the main beam in the basement, attached at the two ends near the foundation wall, and floating about an inch away from the beam. This needs to be done when the clay is just at the right place and no doors are sticking, not too wet nor too dry. Then two nails were installed, one a quarter inch above the wire and one a quarter inch below the wire. A low voltage light system was wired into the system so that when the post in the middle of the house shoved the beam upwards, a light in the kitchen told the homeowner it was time to adjust the telepost one quarter of an inch shorter. When it dropped, the other light would let them know to raise the telepost a quarter of an inch. Small movements like this frequently throughout the year are easy to do and nothing gets forced or cracked.

Gumbo Clay requires an active homeowner because it never settles down.

 


Keywords: Cracks, Foundation, Common Questions, Clay, Soil, Environmental, Mystery

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