Does this sound like enough for a garage foundation.
First would like to say that ive never posted but have learned alot just reading tips and ideas from all on these forums so thanks to you all.Im building a two car garage and was wondering about the slope of the site.From front to back the grade drops about 7 feet over the 24 foot length of the slab.Is it ok to block this up and then backfill with gravel to pour the slab on top of or is there a better way.I was just worried about the block staying true with all that fill and gravel being compacted down then a pad on top of that.Any input would be greatly appreciated.Thanks
Replies
7'
7" in 24' is a lot of fall.
If you use block on a poured footing, you will need to fill each course with concrete and set the bock over #5 rebar stubed out of the footing at 16" o.c.. You will also need horizontal reinforcement in the block. A lot of labor intensive work, when there is an easier solution.
Pour the footing and then a poured foundation wall on it. You will still be contending with the unequal backfill loading, but a poured wall is stronger in resisiting lateral forces than a block wall. Cost wise, if you select a good contractor for the concrete work, you are only looking at a less than $1K increase in cost.
If you do a search of HUDs' web site you can find the federal standard for foundation walls with unequal backfill. I've used the site to check on steel schedules for jobs similar to yours. In addition to the reccomendations there, i would add #4 or #5 rebar at the top of the foundation wall, turned out into the slab (we call them hairpins).
With proper steel placement and cure time after the pour, your job is doable.
You either need to build a full reenforced foundation (with footing to frost depth), or an engineered retaining wall. Then fill needs to be added and properly compacted.
Not a job for a DIYer.
Engineer
Get one, they will know the local code requirements, be able to analyse the soils, and get you a cost effective solution that will last.
Thanks guys for the help.I checked it with a transit today and it ended up being about 50 inches so not quite as bad as I first thought.Im going to be meeting with the inspector and see what he says.I appreciate you all taking time to respond.
Sounds like a good place to do an over and under garage, depending on the land elevations and house.