Getting ready to build a freestanding shop building in my backyard, this spring. Everyone recommends going with a conventional wood framed floor for comfort (easier on the legs and joints). With that in mind, I’m thinking of going with a crawl space. Conventional wisdom in SE Michigan is to use an 8″ wide by 42″ deep trench footing filled with concrete and no reinforcement mesh or rebar. This footing then gets three row of block to create the code required 24″ height clearance in the crawl space. BTW I have heavy clay soil, high water table, and a 42″ frost depth.
Does this setup sound like a reasonable way to go? Do I need some type of mechanical attachment from the footing to the sill plate? Or will foundation bolts grouted into the top row of block do the trick? Any ideas, alternatives or suggestions are much appreciated!
Replies
Greetings Marty,
This post to your question will bump the thread through the 'recent discussion' listing again.
Perhaps it will catch someones eye that can help you with advice.
Cheers
Block yuk, concrete good. For a deep frost line like that, the cost difference can't be that bad. Price out the entire process for both and see. Also check out ICFs.
A less expensive alternative to either block or poured concrete of the normal depth would be a shallow frost-protected foundation. Your footings are very close to the surface with a corresponding reduction in man hours and concrete expense.
If your build site is on somewhat of a then a slab on grade with hydronic radiant heat is an excellent option, whereas a lower build site almost requires a bit of a crawlspace to free up dirt for a proper sloping grade around the building.
We recently built a 1000 square foot cabinet shop utilizing a shallow frost-protected foundation, FastFoot footing liner, Arxx ICF walls, hydronic heat and a window arrangement that gives a moderate dose of passive solar. The result is a basic shop that is very comfortable year round with heating costs near zilch despite being in a windy and cold Wyoming location over 7000 feet in elevation. This is a very good system for cooler climates and can be cost competitive, especially if you are doing much of the building yourself.
Cheers,
Can you give us a website that tells more about the FastFoot thing?
Martyrg,
What size shop are you planning to build? One story tall or two? Sounds to me like a single story building.
Me personally, I would opt for a rubble trench foundation....dig your foundation depth (42 inches) but instead of concrete, backfill this trench with 1-1/2 to 2 inch diameter stone. Install a perforated drain pipe ("French Drain") in the bottom of this trench prior to backfilling, and run this pipe out and away from the site; so as to carry water away from the foundation.
The purpose of this type of foundation is to allow groundwater near the foundation, to have a place to drain. In the winter, the water won't heave up through the rubble stone. By utilizing this system, you would not have to fill the entire 42 inch trench with expensive concrete. For a single story structure, 12 to 16 inch thick pour should more than do it. But, I would run 2 parrellel rods of 1/2 inch rebar in this footer. Put the rods approx. 4 to 5 inches from the bottom. This will add strength to the concrete footer.
You could forego the concrete block and simply build larger forms and pour a single stemwall on top of the rubble trench.
In any case, I would use an anchor sysytem that bolts the wood bottom plate down solid to the actual foundation. I like using 1/2 inch or 5/8 all thread.
If you use block on top of a concrete footer, I would have all- thread rod embedded in the footer, then the block's cell grouted in, and then the wood plate bolted down onto that all- thread. I think that method keps the building tied down better against high winds.
Just my 2 cents.
Davo