Hillside garage - opinion?

[70runner]

Looking at building 3 car detached garage, 2 stalls & workshop, on a hillside. N. San Diego county. The frontal asphalt drive has a drainage slope, approx 5 deg, for runoff down the driveway. Plan to replace the asphalt with concrete in concert with garage build. 2 options:

1. Retaining wall surrounding a steel structure, possibly a 30'W x 25'D kit as shown in pic. The kit runs about 25K including install. Estimate approx 9ft height at rear retaining wall depending on setback needed between structure and wall.

2. Incorporate retaining wall as part of garage structure, then finish with wood or steel. Structure cost would obviously be much higher. Need to research how this cost would compare with separate retaining wall/steel kit option.

Opinions/suggestions welcome...

 

[DuluthMachineWorks]

Personally, I would work out how to incorporate the retaining wall in to your structure. The cost of the wall per linear foot, and the associated excavation, will likely be high enough that you wouldn't want to spend the extra money to make the wall larger than your structure, and you'd need to have a 2-3ft wide access walkway around the steel structure. Then drainage in the gap between the wall and structure becomes a concern, etc. If it were me, I would work with an engineer/contractor that could do the whole job, and design the wall so that the steel structure can bear on to it.

One thing I can say, don't skimp on the waterproofing and drainage behind the wall.

 

[bbxlr8]

Another approach to consider:
I am in a much different climate (PA) but had the same scenario with slope. Mine is stick-built 40'x40 and set into the hill. Construction is poured concrete (much like a basement would be) and ground goes from driveway level to approx 18" high to the soffit in back and slopes evenly on both sides.

FWIW - Project last year was to open up the back roof (is hip) and add a 16'x16' flat face shed dormer with a double door to access the attic space. I am not the original owner and would have done the roof lines different etc. but beggars can't be choosers and I was/am grateful for the space

Edit - can prob guess what may be going in it from your Forum ID

 

[jives]

Not sure why option #2 -- incorporating the retaining wall into the structure -- would be more expensive, unless the retaining wall in #1 is some sort of stepped wall with landscape timbers or concrete blocks as the wall. That could look nice, with a terraced landscaping, perhaps a few of those avocado trees. (I assume you are around Fallbrook?).

In the absence of a nice terraced wall, I would go with #2. Make it such that there is a walk-in entrance on the back (high) side, entering into a loft or attic or full second floor.

 

[mcbane]

I put in a steel garage with an excavation in very hard soil that looks like your option #1 retaining wall. The overall excavation was enormous because I needed room to operate a scissor lift next to the building for erection and maintenance. So I have a 8 ft wide flat path between the building and the cut slope.

Option #2 wasn’t practical or cost effective due to the steel building but would have been easier by simplifying drainage, reducing excavation, and would still have allowed use of a rough terrain scissor lift if that was necessary for construction or maintenance.

So I would go with option 2

 

[adrenalinejeeper]

We faced a similar decision building our guest house/5 car garage combo into a hill (just a bit north of you in Ventura County). After lengthy discussions with our contractor, structural engineer, and architect all together in a room, we decided to go with option #1 for a couple reasons.

-We built an addition to a house before that had an incorporated retaining wall. Even though we went through all the waterproofing steps, I was always skeptical of whether or not moisture was getting through. I didn't want that worry on this one.
-We poured a 5' wide sidewalk (with drains) connecting the retaining wall to the building foundation all the way around that side of the build. The structural engineer loved this as the building foundation being tied to the wall footing provided more slip resistance which allowed for a slightly shallower footing on the wall in his calculations.
-We also built a deck from the top of the wall to the building, covering the sidewalk area. This provided more "tip resistance"(my words) for the retaining wall as it ties it to the building. With the right wall height you could make a bridge of sorts to enter the shop on a second level.
-I liked the additional storage the sidewalk area provided for things like lawn mowers and trash cans.

There were other arguments that I'm sure I'll remember later that swayed us in this direction. None of our people (contractor, structural, or architect) got paid more or less one way or the other. Our simple goal was to go with what would be strongest and provide the best weatherproofing. While it may have cost a little more in concrete and additional siding, I think it was well worth it.

You can check out photos here, scroll down to just past the dirt work photos.

Southern CA Garage/Shop/Guesthouse Build

We are 11 months into the permitting process with the end in sight and should be starting our build any time now. I'll save the lengthy explanation and let the pictures do the explaining for the most part. County codes really held us back, so if something looks unorthodox... that's why. 5...

www.garagejournal.com

 

[slidehammer]

Looking at building 3 car detached garage, 2 stalls & workshop, on a hillside. N. San Diego county. The frontal asphalt drive has a drainage slope, approx 5 deg, for runoff down the driveway. Plan to replace the asphalt with concrete in concert with garage build. 2 options:

1. Retaining wall surrounding a steel structure, possibly a 30'W x 25'D kit as shown in pic. The kit runs about 25K including install. Estimate approx 9ft height at rear retaining wall depending on setback needed between structure and wall.

2. Incorporate retaining wall as part of garage structure, then finish with wood or steel. Structure cost would obviously be much higher. Need to research how this cost would compare with separate retaining wall/steel kit option.

Opinions/suggestions welcome...

I'd much rather have a free-standing structure than one integrated into a hillside. You maintain access to all sides of the building for maintenance and inspection. You give water someplace to go other than inside your shop. Your retaining wall problems don't become building problems.

 

[ddawg16]

Nice looking house.....why ruin the way it looks with the tin shack.

 

[FredWanaker]

I'd start with a conversation with whatever city you are in, in San Diego County, or the county if you are in an unincorporated area. Those cities and counties have some of the strictest regulations in the world, including design and fire codes. I know because I lived there off and on since the 60's. Next I would decide whether to DIY or enlist the help of an architect and engineering firm, surveying etc.. If you decide to DIY better talk with the city or county first, or study their website carefully to find out what level of renderings you are going to need to get the permit. Last, SDG county is very rocky, some N County areas are on solid rock, others not so bad. Better look at that hill carefully to see what will be required in digging down. While unlikely based on the photos, you could hit solid rock 5' deep and need to blast your way to a level pad.

 

[ace10]

Isn't proposed building going to be right in front of your house?

 

[finn]

I seriously considered purchasing a shop built into a hill like that, with the rear wall also serving as a retaining wall.

Fortunately, I passed when I a building closer to the house became available.

A couple of years later, we had a severe rain event, and the hillside behind the structure let go, demolishing the rear wall and taking out part of the roof.

It was rebuilt, but now has a proper retaining wall behind the structure.

 

[jives]

San Diego County averages what, about 12" of rain per year? Proper backfill and drainage will handle the periodic deluge.

 

[FredWanaker]

San Diego County averages what, about 12" of rain per year? Proper backfill and drainage will handle the periodic deluge.

I was there in 1969 when they had torrential rains that washed all the bridges between LA and San Diego away. In 1916 Mission Valley was 50' deep in water. In 1976 or so when that hurricane dumped in San Diego County that came close to happening again when Lake San Vicente almost over topped. One thing about living in So Cal is that when it rains it really rains. I remember 8 inches in 24 hours in Riverside County back about 1979 or so when the drought ended. Here is Riverside in that same 1969 flood.

 

[A747]

I'm located in the Fallbrook/DeLuz area of SD county and am just finishing up my 1000 s/f garage build. Even with 2.5 acres, there just wasn't that many places to place my garage due to setback, septic, and steep slope issues. As you can see from the second picture, we had to stop when we hit the gravel for the edge of the leach field. From the garage to the edge of the 5' slope, there is only about three feet of clearance. After my new roof is done, the contractor will be putting in a 4' high stack stone retaining wall. The first picture shows the roofers setting up the shingles prior to the rains forecast late tonight.

As an aside, under San Diego County code , there is a requirement for any structure over a certain square footage, habitable or not to have a sprinkler system. Mine cost over $20k to install which included trenching approx 300' of 2" PVC line from the main water system to the garage. The ground here is hard and it was jack hammering a trench approx. 24' deep the entire distance

 

[jives]

I was there in 1969 when they had torrential rains that washed all the bridges between LA and San Diego away. In 1916 Mission Valley was 50' deep in water. In 1976 or so when that hurricane dumped in San Diego County that came close to happening again when Lake San Vicente almost over topped. One thing about living in So Cal is that when it rains it really rains. I remember 8 inches in 24 hours in Riverside County back about 1979 or so when the drought ended. Here is Riverside in that same 1969 flood.

I remember those storms (not the 1916 flood of MV!). My brother almost died trying to surf at Windansea in the hurricane. Yup, the rains can come, but it is not like the constant precip of rain and snow year round.

 

[70runner]

Appreciate everyone's comments. I'm in the formative stage, though leaning toward option 1 (separate retaining wall). Hopefully the structure won't require sprinklers Have a meeting with local retaining wall company next week to scope out that aspect of the project.

 

[kbuhagiar]

Appreciate everyone's comments. I'm in the formative stage, though leaning toward option 1 (separate retaining wall). Hopefully the structure won't require sprinklers Have a meeting with local retaining wall company next week to scope out that aspect of the project.

Good luck, I am just down the road in Escondido. If you haven't checked construction costs here in SDC lately, be prepared for a shock. I too am looking at a garage project and I have had to readjust my expectations, a 12 x 40 expansion of my existing 3 car garage is coming in at minimum of $150K.

 

[finn]

I was there in 1969 when they had torrential rains that washed all the bridges between LA and San Diego away. In 1916 Mission Valley was 50' deep in water. In 1976 or so when that hurricane dumped in San Diego County that came close to happening again when Lake San Vicente almost over topped. One thing about living in So Cal is that when it rains it really rains. I remember 8 inches in 24 hours in Riverside County back about 1979 or so when the drought ended. Here is Riverside in that same 1969 flood.

One doesn’t design for averages.

 

[70runner]

Good luck, I am just down the road in Escondido. If you haven't checked construction costs here in SDC lately, be prepared for a shock. I too am looking at a garage project and I have had to readjust my expectations, a 12 x 40 expansion of my existing 3 car garage is coming in at minimum of $150K.

Wowzer. One of reasons I'm hoping to be able to use a steel structure kit.

 

[PWC Repair]

I dug into the hillside with mine, wall is part of my building. I designed it myself with google and common sense. We get about 50 inches of rainfall a year with spring storms commonly bringing 1-2 inches within just hours! I've NEVER had any water come through into my shop. pics in my build thread.

 

[kbuhagiar]

Wowzer. One of reasons I'm hoping to be able to use a steel structure kit.

I wish you the best of luck and as a fellow SDC resident I look forward to more information and updates on your project. My previous response wasn't meant to be a buzzkill, but DEFINITELY get a couple of quotes before proceeding. Contractor/construction costs are like the wild west around here, lol! My first 'ballpark' estimate for my garage expansion came in at $350K.

 

[Copymutt]

Problematic due to runoff. One of the smartest adaptations I‘ve seen involved a second floor drive into from the back. Lower level was waterproofed and back filled, no retaining wall. Buttress stem wall. More expense but, well worth the space.

 

[dcg9381]

I've done it both ways. Retaining wall for me was MUCH less expensive than building it as part of the structure... Basically building a retaining wall was bringing in a dozer, constructing the retaining wall, then treating it like flat ground. At the time it was under $10k for a retaining wall that supported a 30' wide garage.

Building a residence into a hill, about 1500 sqft, basically "walk out basement" - $60k. But that's regional... And I'm in one of the cheaper "regions".

 

[70runner]

Again appreciate the inputs. I've had 2 site visits, one guy said he thought the separate retaining wall was a better option, the other said he'd do an estimate for both options. I'm waiting for visit by a 3rd company that specializes in retaining walls. No numbers yet, except for the steel kit. Got 22K materials quote from local steel barn company for 32' x 24' x 12' structure below.


Pretty much leaning toward the separate retaining wall, though that will require more excavation. I can do some of the excavation myself with this guy.

 

[ddawg16]

One advantage of a not doing a retaining wall.....the ground will help keep it cooler in the summer and warmer in the winter.....well...what little winter you get

 

[70runner]

Cooler in summer is good. Winter this year has generally been rain one day, then 3 weeks of intermittent santa anas with daytime 70-80s, 40s night. Small heater in one attached garage used twice in 10yrs.

 

[BombShelter]

Just saw this thread and thought I'd reply, I used to talk to a lot of people in SD about water issues in hillside homes. It is a big issue but mainly around January. If it was me and the home or garage was brand new I'd look into bentonite membranes for waterproofing. CETCO is my preferred brand with CETCO Swelltite for the walls and CETCO Volclay if you want to go under the floor and footings.

Our garages up here get punishing weather and you can't easily put a drain tile in the garage since most are unheated. The garages that use bentonite for exterior waterproofing never have to worry about leaking, even if cracks develop.

Of course it is the Cadillic of Waterproofing and more expensive than other methods but it's so effective.