Studio: The Foundation
Updated: Mar 12, 2019
Of all the problems this project faced in the planning stages the foundation was the most complex and difficult to resolve. I wanted to build as responsibly as possible and I wanted to avoid concrete as much as possible but the city insisted that the use of concrete was inevitable.
I received numerous quotes for a poured concrete pad which I desperately wanted to avoid. Most of the quotes I received were $4000-$5000 for an 11' x 16' pad. It seemed incongruous to pay that much for something that I didn't want in the first place that in the end would leave me with very cold feet and the earth beneath me with significant damage. There is also an issue of water in the easement of the property that originates from a creek that ran through the property prior to the development of the neighbourhood in the 1950s. We have minor flooding at the far end of the property every spring. That flooding never reaches beyond the easement but as waters rise and climates change around the globe I pause to think.
In light of potential water encroachment I thought my best option would be an above grade pier foundation. Sonotube Piers would be an option. My builder, Sebastian had previous experience working with Perma Columns https://www.permacolumn.com/, an alternate pier system and suggested that it might be a good solution for this project. Both options would use far less concrete than a pad would. Both options would leave a considerably smaller footprint I chose Perma Columns trusting Sebastian without a full understanding of the construction technology. He had done everything up to that point working with us to gain my confidence and I trusted his experience.
In preparation for the foundation I marked the property, easement and hydro clearances and the anticipated footprint within that using stakes and string. My plan was to dig 4"-6" in the area of the studio's foundation of 176sf (16' length x 11' width) and then fill the void with pea gravel hoping that this would help mitigate potential water issues. The labour involved in the removal of 700CF of grass and dirt was again, more than I had anticipated. I enlisted the help of a friend, a professional landscaper and we completed the job together in about a day and a half. We dug to a depth of 4", with a deeper trench around the perimeter and used one yard of pea gravel to fill.
For the foundation I hired a two day labourers for one day. The process was remarkably simple, very straightforward and completed to a high standard. There would be a total of 6 columns. The holes were dug by hand along the edges of the perimeter that I had prepared. The Perma Columns are pre formed concrete and steel posts that are designed to stand on top of heavy concrete circular bases. The bases are lowered into the holes by hand, below the frost line and the columns are positioned on top of the bases. Once everything is squared the dirt is thrown back in the hole to support the columns. From there. they proceed with the framing of the subfloor using 2" x 8" treated lumber, 6" above grade.
For insulation of the subfloor we used 3 x 1" layers of closed cell polyisocyanurate foam core, http://wall.atlasrwi.com/products/residentiallight-commercial/energyshield/) which will provide an approximate thermal value of R20.
Much to my delight the cost of the Perma Column foundation including all materials and labour saved me more than 50% of what a concrete pad would have cost. In this climate and on this property there are a multitude of advantages being above grade. One of the most satisfying aspects of the Perma Column foundation is that there is no permanent footprint and the entire foundation can be dismantled and removed without tools or equipment of any kind.. It is a brilliant system and should I ever build another small structure my first choice for the foundation would definitely be Perma Columns.