Building on Hillside

[mattmountz94]

Looking to build a 32x32 detached garage. Has anyone built on a hillside and designed it for access to the basement along with parking cars/campers on the main floor. My yard is decently sloped. The foundation wall/slab would be approx 13’ from grade on the low side of the slope. This would allow for full size garage door access. There is always the option to just fill in the foundation with fill/stone but the added basement would be a great addition for storage.

 

[PoorUB]

I see no reason you can not, but this is out of the realm of the typical builder. You are looking at steel supports for the second floor and it will be engineered and poured in place or precast concrete panels. She is going to be a heavy bit*#!

Another thing I get concerned about with building on a hillside. I know of two people that did it and both lost thier homes. Granted people build on hillsides all the time. The hillside had been stable for decades, but once the hill side was dug up for fondation work the hill could handle the weight and started sliding down hill. In both cases after moving it they noticed some cracks forming and figured ut was just settling a bit. They had the cracks repaired and they opened up again. One night after a heavy rain they both heard the house shiffting but didn't get concerned until morning and there were cracks in sheet rock 1" wide or more. They went into the basement and the foundation was sliding down the hill. Both cases they tried to go to some extreme measures to save the homes such as driving piles along the fondation and both tried to move the homes, but beings they were on hillsides no house mover would touch them. I saw pictures from one of them with the fondation wall slid over a foot away from the basemant slab. Both homes got cleaned out and demolished and hauled away. Both had insurance, neither company would pay out.

 

[dcg9381]

I think what you're looking for is called "suspended garage floor construction". I've never done it. I have seen a few "elevated" pours of circle drives, but I've never seen a suspended garage around here - I suspect for financial reasons.. There's a thread on it:

Suspended Concrete floor with basement storage

Thinking of having a two car garage built next to my house. Ideally the garage would sit at the end of my driveway. The property slops off as my driveway is elevated. This would provide me much needed shed storage below and a two car garage above... Thoughts on what type of foundation and cost...

www.garagejournal.com

 

[firebirdparts]

Here's my shop. It's a bit heavy duty in the basement. At the time, I think it cost about $20,000 up to the floor. The frame buliding on top didn't cost much of anything. Steel, I paid about $4000 total. That was 20 years ago. They offered to clear span it, but I wanted the post as it's approximately under my lift post. YMMV.

Joe's Garage

 

[billconner]

If you plan to heat it, I'd look at the ICF systems that do floors. If no heat, I'd look at wood framing and a thin non-combustible floor covering like gyp-creet. Not that hard to design structure and subfloor for 4" concrete. Shouldn't be that hard. Does need a stable hill and good foundation especially for the high unbalanced wall.

 

[Pontiac787]

Yes you can certainly do it. My house from 1938 has an upper/lower garage, though it’s only a small 2 car. Be prepared to pay $$$ for a floor on the upper garage that doesn’t leak to the lower garage.

 

[jmarkwolf]

The house I grew up in had a 2-1/2 car detached 2-story garage. The lower level was used for a number of things over the years including heated workshop space. Both levels were at "ground level", so no stairs. The upper level floor was wood planking supported with a single large post in the center of the lower level, but that was a small price to pay. I'm 66, and this garage is among my earliest memories, and is still standing today. The foundation was cement block wall with poured floor and was rock solid.

If I had the option on new construction, I would build something similar.

 

[firebirdparts]

More info: I've seen quite a few over the years of smaller dimensions that were nothing but corrugated decking and concrete. So there is a place for that, but that place wouldn't be 32 by 32. There was another thread on here where a guy built a shop recently, designed by an engineer, in that style, with an irregular footprint, and I think there was supposed to be I-beam framing. As often happens the contractor just did whatever they wanted to. They substituted the proper kind of decking, which is tall, to the improper kind. I am not sure just how unsound that was, but I would be concerned.

We've had lots of suggestions here over the years about post-tensioned, pre-tensioned, precast spans, etc. I am not a structural engineer, but I suppose none of those would be very attractive for mounting a lift upstairs. But your engineer may disagree. My shop was designed by an eminent structural engineer here locally, but I think his design was pretty original. I could certainly be wrong. I work in a factory, and I don't see that it's a typical way to hold up point loads.

 

[dcg9381]

I just completed a residence built into the side of a hill. Cost of building "into" the hill was very very substantial over just filling and doing a large foundation build up on the low side. You're talking about building a basement and then adding enough of a structural steel roof to support inches of concrete and whatever "appropriate" loading is for a garage floor. If you're adding a lift (in addition) - you're way into some substantial engineering territory.

Can it be done? Absolutely. Heck, I've seen rotating lifts that drop cars down into the basement. Can it be done in a reasonable $$ manner? That's all personal budget.

I get why you want the garage up on the top.

Let us know what you come up with!

 

[mattmountz94]

Thank you everyone for your replies. I will have to get pricing to see the difference between adding the basement and keeping it all (1) one floor. A lift would never be added. I am planning to keep a small camper in it though so that does add some weight.

 

[billconner]

The live load is not that great - 50 psf and 2000 pounds over 20 SQ inches. Not that tough.

Code says: "Garage floor surfaces shall be of approved noncombustible material." Surface, not sub-floor and structure. A lot out there.

 

[walta]

When I was looking at houses we say one with stacked garages. It was clear the upstairs garage was leaking and the dripping salty slime into the downstairs garage.

I am sure it could be done well but this one clearly was not.



Walta

 

[oilslick]

Salty water down a hairline crack in the floor, slowly ruining things. That’d be one of my worries.

 

[Max]

I live in a hilly area and it‘s very common to have a house built onto a hill with a daylight basement (open to daylight at one end). A buddy has a 6 car garage with three above and three below and he’s never had any issues. My shop is a 2 car garage under my house and I’ve never had any issues there either. Like a lot of things I think it depends if you get a good builder or not…

 

[firebirdparts]

max, tell us how it was built! Would love to see a picture of what’s holding it up.

 

[Max]

Give me a few days as I’ll have to go over there and ask/take pics.

 

[Brconley]

I just finished a 36x36 two level shop built into a hill. Still getting everything set up, but I like being able to separate the space for different kinds of jobs. Cars and metal work upstairs with wood work in the basement. Suspended slab does cost more but having two spaces versus backfilling with gravel has a lot of upside two.

 

[JamesW84]

If you weren't on a hill would you want to build 2 floors? I thought about what you're talking about, but decided I didn't want to throw all that money in it. I didn't want fill for compaction reasons, so I dug down as far as I had to (6 ft on the high side) in order to get a level pad. I could do a retaining wall, but I just sloped it off.

If you have room, I would just build it bigger and build some walls inside to divide your work areas if you need to.

 

[billconner]

I think whether entry is from up hill side or down hill side affects this. I *thought* I understood OP to be uphill side entry to car storage; sounds like James entered on down hill side.

 

[Brconley]

If you weren't on a hill would you want to build 2 floors? I thought about what you're talking about, but decided I didn't want to throw all that money in it. I didn't want fill for compaction reasons, so I dug down as far as I had to (6 ft on the high side) in order to get a level pad. I could do a retaining wall, but I just sloped it off.

If you have room, I would just build it bigger and build some walls inside to divide your work areas if you need to.

If I had the room I would have built bigger on one level too. Wasn’t an option at this location. Two levels was the best option but more expensive for sure.

 

[mattmountz94]

If you weren't on a hill would you want to build 2 floors? I thought about what you're talking about, but decided I didn't want to throw all that money in it. I didn't want fill for compaction reasons, so I dug down as far as I had to (6 ft on the high side) in order to get a level pad. I could do a retaining wall, but I just sloped it off.

If you have room, I would just build it bigger and build some walls inside to divide your work areas if you need to.

My land is unfortunately all sloped. I really wanted the detached garage at the bottom of my driveway so I could back in trailers or pull my vehicles into it. If I dig down and enter from the bottom it sort of defeats the purpose and would be more for just storage. If I was building on a flat site and had room for a bigger footprint then no I absolutely wouldn't build 2 stories. I am limited to 32' wide with property line restrictions, and the depth is also tricky because the deeper I make the garage the further down hill I am going and the more costly the foundation walls will get. Moving somewhere else on my property isn't really an option as it would defeat the purpose of what I am looking to use it for.

 

[billconner]

Sounds like half of lower level walls function as retaining walls and a beefy second floor structure. DIY or contracting?

 

[mattmountz94]

Sounds like half of lower level walls function as retaining walls and a beefy second floor structure. DIY or contracting?

The foundation/lower level walls and concrete floor would be contracted out. I would possibly look into the framing and exterior finishes as DIY. I am in commercial roofing though and have pretty many hookups for local GCs along with being in Amish country I might possibly just hire it out. Would have to see the cost vs my time and weigh it out. Right now I am just in the design phase and trying to narrow down my build before I get drawings and etc made.

 

[billconner]

If I was doing it, I'd use block - if uheated - or ICFs - if heated - for lower level walls. Could be local conditions that affected that. A precast fabricator near by could change things. In commercial construction it's hard to beat precast walls and concrete plank foods, but still not real inexpesive.

 

[Max]

My friend says that his garage has steel supports with a steel ceiling that was used to support the lower level ceiling until the concrete dried. If you need pics I can get them…

 

[sticktime]

I was planning on doing a similar design but had to scratch the suspended slab due to steel costs. Went from 19k to 40k for a 40x40.
I ended up grading a drivway down to the lower level and built a walk in mezzanine on the top.
Ita doable...its only money!