30' X 40" Garage into a hill

[blake616]

I am in the early planning stages of getting quotes to have a 30' deep X 40' long 3 car garage built. The garage will be set into a hill. The back wall of the garage will mostly be poured walls with side walls that will need to be tapered to match the grade of the hill. Looking for suggestions as to how this should be constructed and quoted?
Has anyone ever built or seen a garage like this? I would like to have one 18 x 8 double door and a 9 x 8 single door. I'd also like to have a service door on one end.

Any help, thoughts or advice would be appreciated.
I can certainly post a picture of the area that the garage will be build on?

 

[73RR]

Easy enough to construct if the GC is talented. Most permitting agencies will want a stamped drawing for the retaining wall, some will accept the designs from the CRSI manual of construction if your soils are similar to the canned designs.
Do not expect the retaining wall to be inexpensive.

How tall do you think the retaining wall will be?

 

[blake616]

I would expect the retaining wall to be at least 10' tall. I have 8' doors planned and would guess that I need at least 10' walls in order to give me room for installation of the doors.

 

[John in OH]

Should be easy with a competent concrete contractor.

BUT, water is your enemy!!! Make sure you put LOTS of drainage on the outside of the walls!! Install perforated drain pipe at footer, partially backfill with gravel, install a second run of pipe mid-way up retaining wall, add more gravel, and place a third run of pipe about 1' below grade at top, and top off with gravel. Route drains to open discharge away from building. Bottom line .... allow NO WATER to accumulate behind the walls!!

Parge retaining wall well before doing any backfill.

Set garage floor top-of-concrete as high as is practical. Excellent builder told me once that 90% of folks set their foundations and floors too low.

By the way, you can get better answers specific to your question if you add your location to your profile.

 

[bjcouche]

It's unclear by your statements if you are trying to build a retaining wall, or you are trying to use the back garage wall to retain the earth. At 8' height, I would suggest using the building as the retaining wall. I would DEFINITLY have this engineered and have the plans stamped by a PE even if not required in your area. Basically you are looking at a structure that's like a house with a walkout basement. Poured concrete is the way to go here. You will require substantial footers as well to keep the wall upright and prevent the wall from toppeling into the garage. I built my 40X64 into a hill and the back wall is 8' tall. The front in the photo is 4' but it's just for show from the front. The front wall could have been 1' tall but I wanted to see the 4' of textured concrete like for wainscoting affect. Based on the cost increase of my building, I'd expect a garage into a hill like that would cost 2-3X that of a garage on flat ground.

Brian

 

[blake616]

Should be easy with a competent concrete contractor.

BUT, water is your enemy!!! Make sure you put LOTS of drainage on the outside of the walls!! Install perforated drain pipe at footer, partially backfill with gravel, install a second run of pipe mid-way up retaining wall, add more gravel, and place a third run of pipe about 1' below grade at top, and top off with gravel. Route drains to open discharge away from building. Bottom line .... allow NO WATER to accumulate behind the walls!!

Parge retaining wall well before doing any backfill.

Set garage floor top-of-concrete as high as is practical. Excellent builder told me once that 90% of folks set their foundations and floors too low.

By the way, you can get better answers specific to your question if you add your location to your profile.

Thanks John.
I am not familiar with the term "parge" in your comment related to the drainage. Also, I will add my location to my profile. I am located in northeast Indiana.

 

[blake616]

It's unclear by your statements if you are trying to build a retaining wall, or you are trying to use the back garage wall to retain the earth. At 8' height, I would suggest using the building as the retaining wall. I would DEFINITLY have this engineered and have the plans stamped by a PE even if not required in your area. Basically you are looking at a structure that's like a house with a walkout basement. Poured concrete is the way to go here. You will require substantial footers as well to keep the wall upright and prevent the wall from toppeling into the garage. I built my 40X64 into a hill and the back wall is 8' tall. The front in the photo is 4' but it's just for show from the front. The front wall could have been 1' tall but I wanted to see the 4' of textured concrete like for wainscoting affect. Based on the cost increase of my building, I'd expect a garage into a hill like that would cost 2-3X that of a garage on flat ground.

Brian

I am using the back wall to retain the earth from the back of the garage. Looks very similar to the lay of the land in your picture. Can you post more picture of your garage that I could use as reference when getting quotes? Thanks...

 

[John in OH]

Parging - noun A thin coat of plaster, mortar or asphalt emulsion for giving a relatively smooth surface to rough masonry or for sealing it against moisture.

https://basc.pnnl.gov/resource-guides/damp-proof-exterior-surface-below-grade-walls

 

[finn]

I looked at a shop like that before I bought my building.

Seemed dry and well constructed, but I concluded that the seller priced the building based on what he invested to construct it, rather than what nearby buildings on flat ground were going for.

Besides pricing, the other deal killer was lack of utility from the rest of the lot, because of the hilly topography.

Conclusion: you're going to spend more than you'll recoup when you go to sell it.

 

[hoho98925]

Look at the concrete portion of my build thread.

 

[bjcouche]

Blake, The majority of the cost in building into a hill like I did was the concrete and dirt work. You can figure out if your general contractor is giving you a reasonable price or not by simply looking at the detailed, engineer stamped plans. calculate how many cubic feet of concrete is specified for , convert that to "yards" of concrete and see what that cost is. Then for the labor of installing the concrete, assume that will cost about as much as the concrete itself. For the building going on top of the concrete walls, well that's about the price of a normal garage on level ground. be prepared for lots of concrete and large footers. Footers will be larger than normally used for a house basement.
Brian

 

[damnet]

Blake,

I'm not sure whether or not this is somewhat your vision. If so, my main expense was dirt, lots and lots of dirt




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[ryan77]

you basically build a basement, then pole barn on top of the stem walls