garage footings

[garageonslope]

I've been lurking for a while but had a questions I can't find an answer to but I'm sure someone on hear will know.

I am planning a garage build on a slopped yard. Garage size is 24 x 30 and slope from back to front is about a 3 ft drop.


I was hoping to pour a stem wall on footings around the building to a height about 2 ft above grade and pouring a floating slab inside. My question is will i need to pour these footings below frost level (42 inchs) or can i pour the footings just below the bottom of the slab. If i were to go to below frost my back stem wall would be 8ft tall and would add a lot of cost to this project.

Any help would be appreciated.

Thanks

 

[ConCretin]

That would be pretty unorthodox and likely to result in problems from differential movement.

Placing walls to frost depth might not be that much more expensive. A little more excavation, a few footing steps and 3 or 4 yards of wall concrete but the cost to run 8' panels isn't much different than 4' panels.

Another option would be a monolithic slab on a structural fill that levels up the pad. The cost shouldn't be too bad but the pad and slopes will take up some space.

 

[u2slow]

I was hoping to pour a stem wall on footings around the building to a height about 2 ft above grade and pouring a floating slab inside. My question is will i need to pour these footings below frost level (42 inchs) or can i pour the footings just below the bottom of the slab. If i were to go to below frost my back stem wall would be 8ft tall and would add a lot of cost to this project.

My building dept/permit required the stem wall to go below frost level. It only goes about 1 foot above slab where its mostly flat. The back wall is nearly 3' above due to the slope.

Have you had your site work done yet? Mine needed significant excavation and proper fill brought in and compacted. Otherwise one side of the shop would have had 12' stem walls in order to land on anything solid.

 

[jkeyser14]

Yes, they would need to go below the frost line.

 

[brownbagg]

it depends on your building code enforcer, I have seen some in a garage that was just a mat, and the whole building rock and roll during the freeze, that because the building is not a resident and most time be unheated. it depends on your local. another way would be to use sonic tube piers and grade beams

 

[rburke65]

OP....have we done this before?...any construction experience?

 

[LoTec]

My shop addition is on a significant slope. The original grade dropped about 32" over the 24' width from north to south.

It's a pole building. I set all the poles 4' deep. The treated posts for the south wall also serve as a retaining wall. The bottom 32" of the posts (above the original grade) have foundation grade treated 2x6s nailed to the inside surface, covered with a heavy poly sheeting and 2" high density foam. Between the posts are "bookshelf" 2x6 girts (treated 2x6s the bottom 32", and filled with 5-1/2" of styrofoam). The outside is covered with pole barn steel sheets.

I had about 40 yards of fill sand delivered and spread to level the floor inside. Before the sand was added, for extra bracing I installed a "deadman" anchor: a 16' 4x6 treated post laid on the original grade about 8' back from the retaining wall, thoroughly staked so it can't move, with steel rods attaching it to the wall posts. The wall did not bulge when the fill was added & compacted, or since.

It's been five years, and the wall and fill seem to be working out well. I just got around to pouring a concrete floor this summer. We'll see how it holds up.