"Wing" insulation, drainage and parging.

With the foundation insulation done, it was time to turn my attention to insulating the ground around the foundation. This insulation for the ground is sometimes called "wing" insulation and is an important part of the FPSF foundation design. The wing insulation effectively protects the shallow footings from frost heave by raising the frost line towards the surface. In my case the insulation plan called for R20 insulation extending outwards 4' from the footings but 6' at all corners (except where the footings were more than 6' below final grade).

The colder the climate, the higher the R value the wing insulation must provide to keep the earth below from freezing. Also, the colder the climate, the further the wing insulation must extend outwards from the foundation. When the underside of the slab and footings are insulated as well, the R value of the wing insulation must be increased more still since reduced heat loss from the underside of the foundation will contribute less towards keeping the earth under the footings from freezing.

Installing the wing insulation was pretty straight forward. I prepared the ground around the foundation using a 36" landscaping rake. I worked at the gravel to create a slight downward slope away from the foundation then raked the surface smooth. The wing insulation should slope slightly downward away from the foundation so as to prevent water that soaks into the soil above from pooling against the foundation. Once the surface was prepared, it was a simple matter to lay out the insulation boards. Once the boards were layed out I applied a peel-and-stick water proofing membrane over the boards and partway up the slab edge insulation. The membrane is very useful here in that it creates a drainage plane, protects the rigid foam and helps tie all the boards together to make a "skirt".

Peel-and-stick membrane does a great job of tying the insulation together into a "skirt". I extended the membrane 6" up the slab edge insulation - 2" higher than the 4" weeping tile shown in this photo. There were no issues with the "skirt" coming apart or pulling away from the slab edge.

Once the "skirt" was completed, I used an acrylic parging compound to finish the rigid foam at the slab edge and at the top of the basement walls. Because of the heat last summer, I spent my mornings and evenings working on the south facing surfaces and the middle part of the day on the north, east or west facing surfaces. Nevertheless, I had to work quickly since the parging compound would set up quickly even when not exposed to direct sunlight. Lastly, I installed 4" weeping tile around the entire perimeter of the foundation and then drained the weeping tile down slope to daylight.

In this photo you can see how the "skirt" varies in width from 4' along the edges to 6' feet at the corners. I applied 2 coats of  parging to the slab edge insulation along the walk-out side since this side would be backfilled to final grade straight away. We backfilled by first raking out a layer of sand over the "skirt" to the depth of the weeping tile then followed that with a layer of clay. The waterproofing membrane and sand work together to facilitate drainage away from the foundation while the clay cap helps keep water from penetrating through the surface. The backfilling was done when the weather was dry. Work with clay - especially grading with a rake - is best done when it is dry and "crumbly".

I applied only one coat of parging to the top of the wall prior to backfilling since this portion was backfilled only to within about 18-20" of the top of the basement walls. Final backfilling and grading will bring the final grade to within 12" of the top of the wall, and I will be applying a second coat of parging prior to this operation. 

Do You Recall - Royal Wood

I saw Royal Wood live (as a solo act) in Thunder Bay over the weekend and really enjoyed the show - he's definately worth seeing if the opportunity presents itself.