How to Insulate the Floor of a Crawl Space in Alberta, Canada

Insulate the walls of your crawlspace from the outside.

Alberta winters can be cruelly cold. You can save money and keep your tootsies toasty by insulating the crawlspace of your home. Because crawlspaces often contain ducts and pipes that must be protected from freezing, Natural Resources Canada recommends insulating the walls of a crawl space rather than insulating the floor above the crawl space. Insulating from the outside will decrease moisture problems inside your home and, if the footings of your crawl space are above the frost line, prevent frost heave.

Things You'll Need

• Shovel<br /><br />Tarp<br /><br />Wire brush<br /><br />Scraper<br /><br />Parging material<br /><br />Waterproofing compound<br /><br />Flashing<br /><br />Exterior caulking<br /><br />Measuring tape<br /><br />Rigid insulation (glass-fiber or polystyrene board)<br /><br />Utility knife<br /><br />Corrosion-resistant fasteners and washers<br /><br />Protective coating for insulation

Instructions

1. Dig a trench around the outside of your house. This can be done by hand using a shovel or by using a back hoe. Never dig down past the footings. Store the excavated dirt on a tarp at least 24 inches from the house. Protect the trench from the elements and people from falling into it.

2. Clean the surface of your foundation with a wire brush and scraper. Check for any cracks, holes or other damage and repair as necessary.

3. Parge any uneven surfaces and allow to dry.

4. Apply two coats of waterproofing compound to the outside of the foundation from grade level to the top of the footings.

5. Ensure that any penetrations through the foundation wall are sealed, removed or will extend far enough past the insulation.

6. Install flashing approximately 6 inches above the header area. Use "Z" flashing if the house is sided. For a brick house, use a metal "J" channel or wood flashing. Wood flashing should be installed after the insulation. Seal the joint between wood flashing or "J" channels and the house with exterior caulking.

7. Cut the insulation to the correct height, measured from the flashing to the top of the footings. Start at a corner and keep the boards as close to the wall as possible. Overlap the insulation at each corner. Hold the insulation in place at the top with the flashing and corrosion-resistant fasteners and washers. Insulation below-grade will be held in place by soil.

8. Protect the exterior of the insulation from sunlight and other damage by applying a covering from the top of the insulation to approximately 1 foot below ground. Options include polymer parging material, pressure-treated plywood, siding to match the house siding or metal lath with cement parging. In all cases, follow manufacturer's instructions.

9. Fill the excavated hole. Use 6 inches of gravel over the drainage tiles and then add the soil incrementally, tamping it every so often. Ensure the soil slopes away from the house--8 inches over the first 6 feet is a good guideline.

10. Cover the excavated area with a surface of your choice, allowing sufficient time for the soil to settle.

Tips & Warnings

• Insulating a crawlspace from the outside can be time consuming, hard work. Allow several weeks to complete the job.<br /><br /><br /><br />Insulate from the inside of the crawlspace wherever there are obstructions preventing exterior insulation, for example a porch.<br /><br /><br /><br />While you are excavating around your foundation, check the condition of your drainage tiles and enlist the help of an expert if there appear to be issues.<br /><br /><br /><br />Some insulation experts recommend applying two layers of insulation board so that seams can be overlapped to prevent air and moisture leakage.

• Consult an expert if you live in an area with unstable soils, as the excavated area will require bracing.<br /><br /><br /><br />Do not use rigid glass fiber board insulation to insulate the exterior wall of your foundation if you will not be applying the insulation all the way to the base of the foundation, if there are no drainage tiles or if there will be horizontal seams in the insulation.<br /><br /><br /><br />Make sure surface water is routed away from the newly insulated foundation.<br /><br /><br /><br />Ventilate your crawl space in the spring and ensure that vents are closed and sealed before winter.

References

• Natural Resources Canada: Keeping the Heat In