# Garage footer / slab advice



## smaj100 (Oct 17, 2012)

Ok folks I need some advice from those who have done this and are much smarter than I am.

Sitrep: We are building a 30'x40' steel square tube garage in a few weeks. We are in Middle TN, soil is heavy clay with A LOT of rocks. The site has about 5' slope from front to back. I know I am going to need 60-80 ton of rock to fill in the site once we decide on the footer.

Problem is I've had 2 different concrete guys give me 2 different solutions for the footer/slab.

Guy 1: Monolithic slab, in my mind this will just be resting on the surface as the way it was explained to me everything is formed on grade and built up. This is super expensive as the amount of concrete is massive.

Guy 2: Dig in traditional footers, build up the retention wall in the back with cinder block and around the sides, then pour a 4" slab after leveling with rock. Cheaper sounds more stable to me. 

My concern with 2 is it will be almost 7-8 rows of cinder block on the high side at the back wall. That is alot of pressure from the rock and slab pushing out on the wall. I'm not an idiot but know when I am outside of my area of expertise. Can I save some money by doing some of this work myself and try to strengthen the structure myself?

I am wondering if I drystack the cinderblock on the footer using the rebar they will set in the footers and then pour concrete in every few voids of the cinderblock to tie them together and bind them into a more solid structure?

Any suggestions or advice is greatly appreciated.


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## TheLazyL (Jun 5, 2012)

I'd get a third Contractor. I wouldn't tell him what the first 2 said to see if his proposal aligns with one of the first 2.


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## camo2460 (Feb 10, 2013)

Number 2 is how I did it when I built my house. I had a 3ft. slope from front to back, I built a retaining wall in the back, leveled it all with gravel and then poured the slab after digging footers. I only had to dig three footers as the front of the house sits on bedrock. I still have some of the steel form stakes that I drove into the bedrock at the front of the house, which I had to cut off, because I couldn't pull them out with the truck and a chain.


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## bacpacker (Jul 15, 2011)

Our basement back wall sits 10 courses below grade. It on footers with rear and poured the voids in the blocks. It hasn't moved in 20+ years. We have heavy clay at the house as well.


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## smaj100 (Oct 17, 2012)

I'm no mason, are these blocks drystacked or traditionaly done with mortar joints?


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## bacpacker (Jul 15, 2011)

Mine has motar. I wouldn't trust dry stack with several feet of dirt leaning on it.


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## Caribou (Aug 18, 2012)

Either way should work though I agree with backpacker that I would not dry stack the cinderblock. If you go with the cinderblock then mortar the joints and use rebar and fill those voids. If the wall gets very tall you might want to consider weep holes and/or a deadman. You will need to give any mortar and concrete time to cure before you proceed to the next step.

You need to level the ground before you pour the slab. Your options are to build a retaining wall or count on a shallow embankment for your ground stability. Either option will work if done properly. A long slope will not fall over and a wall is less likely to be damaged by rain or flowing water.


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## IlliniWarrior (Nov 30, 2010)

keep in mind you're in the Madrid Fault area .... wouldn't be going with just a slab - especially with that much slope .... footings down well into that clay .... either the block & rebar or a form a poured concrete wall - they have the insulated styrene forms now that are almost DIY .... 

check the overall cost of boosting up that 4" slab - that's not much support for the bigger vehicles ....


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## cowboyhermit (Nov 10, 2012)

I am no concrete expert, and most of what I do know is based in a crazy climate. If you build a retaining wall apart from the building then there are a lot of ways to build a good retaining wall, many of them cheaper than cinder block, even tires for instance or the interlocking blocks. Or like mentioned above, just mellowing out the slope so one isn't needed (2:1 or whatever is appropriate to your area).

Personally, what we have done in similar circumstances, is just pour a pony wall or two, tied into the slab. We have not had great luck with cinder blocks though, so maybe there is a bias.

Despite supposedly being in the flat prairies, finding a level spot on our homestead is a fool's errand so pouring a slab is never a simple thing.


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