Home Improvement Contractor - Licensed Contractors
Advice for improving drainage around home addition on a grade-beam.?
We have a 378 sq.ft. addition on our bungalow and live in a northern climate with central heat. The original structure has a full basement. The addition is built on a grade beam with concrete walls extending just below soil level. The soil conditions in our area are heavy clay (poorly drained). The contractor cut a hole through the basement wall into the crawl-space of the addition for plumbing and heating ducts and left considerable extra space for cold-air return from the crawl-space back to the basement (and furnace). We have had a problem since the addition was built with mice burrowing under the walls of the addition and getting into the main basement. As well, we have just discovered that the contractor lined the concrete walls with fibreglass insulation and gyproc which have become rotten and black-mold. We have pulled out all of the insulation and fibreglass. How can we improve the drainage to reduce the dampness in the basement, and how can we keep the mice out?
Public Comments
- Sounds like there wasn't a structural engineer involved in this project. If by heavy clay you mean a fat clay with a PI greater than 35, you may get some differential movement due to the volumetric changes in the clay as the moisture content of the soil changes. This will be magnified by the difference in the bearing depth. Clay being impervious and the near surface soil changing volume more often with greater magnitude than the soil at the bearing level of the original basement. And what about your code required depth of foundation to get below the frost line? You may also end up getting some differential movement due to frost heave. Is there ventilation in the crawl space under the addition? Seems like most of the problems you asked about are easily fixed. I suggest getting a qualified remodeling contractor out to take a good look and give you an estimate. If you start noticing resultant distress from foundation movement like doors going out of adjustment and drywall cracking, you may also want to talk with an engineer. Maybe a lawyer too.
