Building a Garage Into a Hillside

[300Deluxe]

Getting ready to have some dozier work done on my property in preparation for a 40x60 garage. I wanted to get your opinion of building a garage into a hillside, below grade of the high side.

I will be demo'ing an old unfinished house foundation that was intended to have a basement. So my plan is to somewhat replicate the block foundation shown in the pictures below, but on a larger scale, and obviously taller. The old block walls form a 30x50 footprint. Mine will be slightly larger at 40x60.

My garage door(s) will be on the gable end, and the slope shown in the pictures will be hogged out into a flat area in front of the garage. I'm thinking a retainer wall will be necessary there, perhaps an extension of the wall against the hillside.

My question to you is, if properly executed (french drains, etc.), will I have moisture issues building my garage into this hillside? My budget isn't big enough for fill dirt to bring the low side level with the high side, and I would worry about settling issues.

Please disregard the "graffiti" on the old walls here. It's not visible from the road.... The brush will also be cleaned up, obviously.

 

[Richard Cranium]

Just remember that the wall on the hill side is a retaining wall and should be engineered for the type of soil load.

 

[300Deluxe]

Good point.

I should also note that the dirt work will be performed at least a year ahead of any footers being dug, or any other necessary subsequent work. So I'm likely looking at have a skid steer touch up any run-off or fall-in of dirt from the weather.

 

[jmarkwolf]

We had a two story garage when I was growing up, with 3 walls into the hillside similar to your scenario.The added space afforded by two stories was wonderful. 4-stalls of space in a 2-stall footprint.

I try to convince anyone building a garage or shop with a walk-out scenario to make it 2 stories, rather than just a foundation and a single story. Although it does complicate options for the floor of the upper story. I didn't have a walk-out scenario so I had to build my new 2-story shop "upwards".

http://www.garagejournal.com/forum/showthread.php?t=221281

Can't comment on the specific construction details of my dad's garage, as it was built before my time (some time in the 1940's), other than walls were cement block, the floor poured concrete, and the floor of the 2nd story was wood, as was the frame, walls, and roof.

I remember it being damp in the "basement of the garage" but my dad had installed a gas furnace that made it nice and toasty when needed.

Enjoy your project, and keep us posted.

 

[jwhcars]

I'd cut the hillside back as far as you can, no dirt against your walls. I think with proper drainage you will be ok. If you can't grade the hillside then you may need a proper retaining wall.

 

[Pen & Wrench]

My brother-in-law did that, a little smaller, 25 by 50, two story. His wall is poured concrete, designed to take the hillside load. His turned out very nice. Upstairs has some living space which my wife & I have stayed in several times. You're gonna love yours.

 

[dutchgray]

I'd cut the hillside back as far as you can, no dirt against your walls. I think with proper drainage you will be ok. If you can't grade the hillside then you may need a proper retaining wall.

This if you can afford the extra digging and retaining wall. Don't have dirt against a building wall above floor level unless its your only option.
Many ways to build a retain.

 

[300Deluxe]

Thanks for the input guys.

I could cut back the high side, but the road is about 60' away, and the slope would need to begin at the road. I think that would be a bit of an eye sore and would eliminate what little bit of flat lawn I currently have (hilly here in middle TN).

My fear is having dampness issues and/or a leaky wall, similar to a basement scenario. Although, I would have two walls completely exposed. I'll talk to some block guys regarding proper reinforcement for soil loads. The current old block walls are split an are caving in.

 

[theoldwizard1]

I am no soils expert, but I would be very concerned about that hill moving. Of course, if it has not cracked the wall that is there, then I would feel much better. Still, I think I would want some tieback/deadman buried in the hillside and connect to a some reinforcing steel (C channel) on the inside of the garage.

As for water proofing start with drain tile just below the level of the floor on the hillside and come around both side of the garage and run it to daylight. I prefer the solid kind with a sock over it. The walls need to have a "good" asphalt based coating and then drain board. Back fill with gravel.

 

[theoldwizard1]

I'll talk to some block guys regarding proper reinforcement for soil loads. The current old block walls are split an are caving in.

Block may be cheaper than a poured wall, but you need it tied to the floor/foundation with lots of rebar. Get a quote on running rebar in every cavity and then filling every cavity all the way to the top.

You still will need some deadmans installed in the hillside and connected to steel on the inside.

Hillsides that have been cut into move over time. Period.

 

[ScottsGT]

My house is built this way. 10" of poured concrete walls for the foundation that come about 24" above the soil on the high side.

 

[crazytrain]

I see no problem at all with what you are doing as long as you take the time and plan the build. I would go with poured walls engineered for the soil load, then spend the time and money to properly water proof them with tar/water proofer. Add drainage pipe to carry the water around and away from the foundation and back fill with compacted stone. I would also recommend the foundation be at least 1-2 feet above grade to keep water from getting up under the siding. Water run off should pass through the stone and be carried quickly.

 

[ScottsGT]

^^^ Exactly how my house is done with the drainage.

 

[Denwood]

My folks' garage is exactly this. 30x30 on the main floor (garage) with the top floor a large wood shop. It's built into a hillside with block walls. About 25 yrs and counting with no issues.

Just ensure your wall on grade is built to spec, and drainage is done correctly.

 

[Jlbc212]

My garage is also built into a hillside. 10" poured concrete walls coated with gooey tar foundation coating, drainage pipe at the footing level and 3/4" stone backfill against the wall. The garage stays cool in the summer. I do run a dehumidifier to absorb moisture.

 

[larry4406]

No problem with the garage built this way. Adequate foundation strength to resist the backfill and waterproofing and drain tile to keep it dry. Daylight the draintile on the low side. I personally like poured concrete foundation walls vs cinder block.

Your grade looks quite favorable to have the garage on the lower level while you can have an attic space on that top that walks out to grade (storage, inlaw suite, etc). That is what I did on my prior garage. I used attic trusses that spanned 28' deep so I did not have any steel. The attic walkout condition was on the truss gable side.

 

[jb3]

I have an old garage building built like this without any drainage consideration, and water through my walls is a major issue, so x4 to major focus on water drainage.

Im hoping to mitigate some of the problem a little bit with a deep french drain at some point, but a dehumidifier will always be present i think

 

[volleyball]

Building into the hill is the best way to do it. Use the garage wall as the retaining wall. Makes no sense to build two. This thing is done all the time where people have basements. I'd do a poured wall at 5000 psi. Better moisture resistance. Seal the outside of the block and add a weeping membrane and two runs of drainage. One at the bottom and one at the top. I'd also grade the hill to the sides of the garage. Nothing drastic, just enough that the water will tend to flow around the garage instead of into.
Are you going to use the hillside as access to the upstairs? If you are going vehicular, I'd make the floor out of prestressed concrete panels.

 

[300Deluxe]

I've seriously considered a second story as living quarters or storage with access from the higher side. Possibly even a neat little porch facing the road. Not sure how tall that would make the overall structure, as I want enough ceiling clearance in the garage for a lift. The high side is only about 6'-7' above the low side. So that would put the access door a good ways off the ground I'm thinking.

I'll ask a contractor friend about high strength concrete on the soil sides.

 

[Kevin54]

Coat your walls, but they also make a waterproof membrane for below grade that will channel the water down to a tile. Once done properly with a membrane, you will never have to worry about water or moisture weeping through. To save money, I would use a poured foundation that is below grade, and use block for the rest.

And remember that you don't have to have a foundation all of the way around like is currently shown. Out front, and on the partial sides, you can have a standard footer with blocks out of the ground, and build your wood walls above that. If that doesn't make sense, take a look at the pic you posted. You are showing a block wall all the way to the front, and even framing in the door. This can all be done with wood on top of a block foundation. You don't need walls or blocks on all 4 sides 10' tall. Just remember though that if you are going to be building a garage that is 10' or taller to have a lift, by building tht tall, the studs have to be 2x6 instead of 2x4's, or at least around here they do.

Here is the membrane I was speaking of to waterproof your foundation