Print This Page

DayCreek Journal

October 24 , 2011

Garage / Workshop - Part II
FPSF - Frost-Protected Shallow Foundation

After weighing whether to do another rubble trench foundation or FPSF (Frost-Protected Shallow Foundation), I decided to go with the FPSF for a few reasons:

  • As I found out when we built our house, there's a ton of rock buried deep in the soil. Not that this was a show-stopper, but it made the rubble trench wider than it needed to be, requiring more fill.
  • Being a mostly unheated structure, putting down foam board around the perimeter seemed a better solution to frost-heaving.
  • Since I had never done a FPSF before, it's always been an option that I wanted to try.

Here's a pictorial of how the foundation was constructed:

breaking ground

In August, an area approximately 60' x 50' was excavated, leveled and filled with washed gravel. This was left to settle for about a month before any concrete work was to commence.


In September, the footing was poured for the back wall of the foundation. As in most of SE MN, nothing is flat and our only option for the garage was to build it into a hill. This required a 4-foot high wall.


back wall being poured

The back wall being poured.


Post bracket

Here's the back wall with post brackets in place. These are set directly into the concrete . This makes for an incredibly strong connection between the posts and foundation. If I were building a tradional cordwood structure, I wouldn't have bothered with these beefy brackets, but this structure needs to stand on it's own w/o cordwood walls.


garage floor drain

One thing for sure...this garage is having floor drains! It's a major pain to constantly have to squeegee water off of garage floors during the winter -- this will definitely help.


radiant floor installation

At this point, I'm not 100% sure how much and what part of the garage/workshop will be heated, but I wasn't going to have a garage floor poured w/o the tubing underneath. Ya can't go back and add it later!


garage floor being poured

The floor gets poured in early September.


The perimeter of the foundation has drain tile installed to move water out away from the building.


foam board insulation underground

After the drain tile was laid, a layer of gravel was put on top followed by foam board.


landscape fabric applied over drain tile

A layer of landscaping fabric is put down over the foam board to prevent silt from clogging up the drain tile below.


drain field

A drain field was dug into a low spot outside the foundation perimeter for the garage drains.


foundation complete
Here's an image of the foundation/floor completed. Lots of gravel was used to create a large drain field as well as to cover the foam board installed below grade around the perimeter.

So there you have it. Next year once the ground has compacted/settled over winter, I'll pour a driveway apron for at least the 2-car section of the garage and maybe the single bay as well.

Now onwards to building the frame of the structure...

—Alan Stankevitz