Garage Basement Question

[7th Kahuna]

My dad and I are planning to construct a new garage / shop building here in Los Angeles County. The city is really particular about what we can and can't do. Because this building will be constructed prior to demolition of the existing garage we are very limited as to square footage and similarly because the original house is on a slab with a low pitched roof we are limited in height.

I have been kicking around the idea of a basement space. My dad is certain it will be too expensive.

We are planning to construct the ground level portion using either concrete masonry or concrete filled Styrofoam blocks. The structure will be approximately 24' x 25'.

Does anyone here have an idea of what sort of additional cost we would be looking at for the basement? I am only really concerned with the excavation, increased footing size, below grade walls & waterproofing, and the ground level structural floor. We could handle all of the utilities and finishes, wall furring etc at a later date; money and time permitting.

The site has easy equipment access and no soil or water issues I am aware of.

I am hoping to have room for a few of my own tools in the garage, so I really need a place for my dad's collections.

Seriously, if it were at all reasonable, I would hate to miss the opportunity to create the additional space.

Thanks guys. Even some unit prices would help.

 

[KPSquared]

I would be surprised if you could have that done for less than $50,000. That's a lot of engineering and concrete structure.
Unless I'm reading you wrong? You want a basement you can park on, correct?

 

[7th Kahuna]

I would be surprised if you could have that done for less than $50,000. That's a lot of engineering and concrete structure.
Unless I'm reading you wrong? You want a basement you can park on, correct?

Yeah, need to be able to park on it. Wondered about pre stressed concrete 'panels' for the floor but could also be wood timber, steel ibeam, etc. Don't know if any of that might be pre engineered for this purpose.

 

[38Chevy454]

Put the basement area under the house, so conventional flooring support can be used. The grade-level garage is just a slab, nothing underneath.

Excavating under an exisiting house will not be cheap or easy.

 

[bczygan]

Some questions.

Why must you demolish the existing garage?
If you must demolish it, why can't you demo it first?
Can you modify the house roof to make it higher and then have a different basis for the garage height?

 

[IHI]

Contractor friend of mine bid a garage where homie wanted a full basement under his 28x48 garage. The cheapest option in the area for the garage floor was Coredeck, concrete panels with hollow tube area's in them, floor alone for the material, crane/setting was just under $55,000 10yrs ago.

Obviously you wont know until you do research and make some calls the true cost in your area, but it wont be cheap and will have to have an engineered print/stamp prior to permit even being issued since the city will have a huge stake on this type of project...if they allow it and something happens, they are 100% liable in court since once they give the okay they too essentially own your project and any problems that may arise/result in injury/death.

 

[7th Kahuna]

Put the basement area under the house, so conventional flooring support can be used. The grade-level garage is just a slab, nothing underneath.

Excavating under an exisiting house will not be cheap or easy.

My dad and I hand dug a small utility basement under an existing house when I was a teen. That was not a fun job. In this case the house is on a slab so a basement would not be a good option.

 

[7th Kahuna]

Some questions.

Why must you demolish the existing garage?
If you must demolish it, why can't you demo it first?
Can you modify the house roof to make it higher and then have a different basis for the garage height?

The existing garage is in bad shape and very small. It will be removed to make way for a future house addition. There are a couple of issues with removing it prior to the reconstruction of the house however. As for the house, the city will not let us touch the roof line. Ironically the house is about as plain-jane as you could get (with a 3 in 12 pitch in a neighborhood of 6 in 12 pitched cottages) but because it is located within a historic overlay it is treated as though it were a princess. A sensible fellow would have pushed it over and hauled it away. The only path to changing the roof line will be 'historically sensitive' 2nd story addition to our fabulous '49 stucco box. Can't complain too much however, at least they are letting us build the new shop.

 

[7th Kahuna]

The cheapest option in the area for the garage floor was Coredeck, concrete panels with hollow tube area's in them, floor alone for the material, crane/setting was just under $55,000 10yrs ago.

Wow, would not have guessed the concrete panels would be that expensive. Definitely have more research to do.

 

[kbs2244]

This is time for a City Code Specific Architect.
There is nothing you can do that will not be inspected 12 times by 4 agency’s.

 

[7th Kahuna]

So far walking into the city and sounding like we know EXACTLY what we are doing has worked pretty well. We answer the questions we want to answer before they ask and try to slip the other issues by. They offered that they MAY be able to approve the new garage over the counter. That of course will be out the door if we go with the basement I'm sure.

'It's not a basement, it's an 8 ft radon gas diffuser / fresh air exchanger.

 

[Zeke]

With the low pitched 3:12, you could go max height (I assume 13') and construct a mezzanine style storage place. L.A. County will make any kind of excavation and construction stupid expensive.

If this was back in the 50's, you could tell them this is a bomb shelter.

 

[7th Kahuna]

With the low pitched 3:12, you could go max height (I assume 13') and construct a mezzanine style storage place. L.A. County will make any kind of excavation and construction stupid expensive.

If this was back in the 50's, you could tell them this is a bomb shelter.

You hit it on the nose, about 12'-8" as we don't seem to be able to exceed the height of the house. Unfortunately the garage roof must match the house. We had thought about a mansard style roof. I'm game for the bomb shelter. I read an article the other day questioning what happened to all the private bomb shelters built in the 50's. The author's point was he never hears about people digging them up or discovering them in the basements of their houses. I can't say that I have either. Fewer basements in LA I suppose.

 

[krj]

My full basement only cost about 5-6k$ more.

http://garagejournal.com/forum/showthread.php?t=50008

Best money I ever spent!!!

 

[7th Kahuna]

My full basement only cost about 5-6k$ more.

http://garagejournal.com/forum/showthread.php?t=50008

Best money I ever spent!!!

Thanks for the link, I'll check it out.

Very nice! That appears to have been a 100% poured in place job (basement walls and both floors) yes?

 

[krj]

Nope. Walls were poured as a normal foundation is. There was a 2'' x 9'' key in the top of the walls. The floor was then formed from below and poured after. 9'' thick floor with a ton of rebar...

 

[bczygan]

The existing garage is in bad shape and very small. It will be removed to make way for a future house addition. There are a couple of issues with removing it prior to the reconstruction of the house however. As for the house, the city will not let us touch the roof line. Ironically the house is about as plain-jane as you could get (with a 3 in 12 pitch in a neighborhood of 6 in 12 pitched cottages) but because it is located within a historic overlay it is treated as though it were a princess. A sensible fellow would have pushed it over and hauled it away. The only path to changing the roof line will be 'historically sensitive' 2nd story addition to our fabulous '49 stucco box. Can't complain too much however, at least they are letting us build the new shop.

So the 2nd floor addition will solve the height problem.
What are the reasons for not demolishing the garage first?
What prevents you from knocking down the house and building what you want?

 

[Zeke]

So the 2nd floor addition will solve the height problem.
What are the reasons for not demolishing the garage first?
What prevents you from knocking down the house and building what you want?

No, not necessarily. Most of SoCal no longer allows detached garages with 2nd stories. Not trying at all to be political, but the main reason seems to be they are often converted to illegal residences.

Real estate is expensive here.

 

[7th Kahuna]

Nope. Walls were poured as a normal foundation is. There was a 2'' x 9'' key in the top of the walls. The floor was then formed from below and poured after. 9'' thick floor with a ton of rebar...

Sorry, that was what I meant. I just wanted to be clear that you had not used any sort of pre-formed panels, beams, or the like to support the garage level floor. As I see it you formed a wood base and poured the concrete over it (with a whole lot of steel => here in earthquake country that kind of goes without saying ).

I'm amazed you got it done that cheaply but it is not too far off what I was thinking either. I believe my dad would bite if we could keep it in the $12k to $15k range. If cheaper, it would be a no-brainer.

 

[bczygan]

No, not necessarily. Most of SoCal no longer allows detached garages with 2nd stories. Not trying at all to be political, but the main reason seems to be they are often converted to illegal residences.

Real estate is expensive here.

Sorry Zeke.
I meant making the house 2 story to get the garage higher, not 2 story. Also making the house 2 story gives you more lot for the garage. Need more info on what the overall plan is, and the budget and existing conditions. He may have other options.

 

[7th Kahuna]

So the 2nd floor addition will solve the height problem.
What are the reasons for not demolishing the garage first?
What prevents you from knocking down the house and building what you want?

We're getting ahead of ourselves here. The second floor addition, if built now, would solve all sorts of problems. From the city's perspective, the house drives everything else on the lot. Once the new house height were approved, it would apply to the garage as well. Zeke is right though, the city is definitely on the lookout for 2nd units. When they are approved you must basically sign your life away with the promise they will only be used as an office or mother-in-law's quarters, never rented. That said, we have talked about beefing up the foundations of the new garage so that a second story could be added after the house is remodeled. The city limits the percentage of the lot that can be covered by 'roof' so that even the remodeled house won't be all that large. A bonus room over the garage would be nice.

As noted, there are a couple of reasons for not demolishing the existing garage. One is that it is original to the house and effectively hides the new structure from the street. We have a little bit more freedom with the city because of this. Perhaps more importantly however, this property is going to be rented for the time being and the tenants must have access to a garage and they will have the old one. The new garage will be accessed from the alley rather than the street. The whole point of adding the new shop building is to give my dad and I a place to work on a handful of projects that have been waiting far too long. So until we do remodel the existing house, we really need two garages.

As to the house itself, because of the historic overlay, the city prohibits us from tearing down the house or altering it in a way that detracts from the feel of the neighborhood. Most of the homes here were built in the 20's and 30's - some later, some earlier, but the homes of those eras were smaller and had a lot of air around them. The city wants to maintain that feel even as the interiors are modernized and the termites evicted.

 

[7th Kahuna]

Sorry Zeke.
I meant making the house 2 story to get the garage higher, not 2 story. Also making the house 2 story gives you more lot for the garage. Need more info on what the overall plan is, and the budget and existing conditions. He may have other options.

So I think you are getting the idea. The immediate plan is to update the house enough to get it rented and build the new shop space to use for ourselves. My dad is 75 and we have had a few projects on the books for years now. Down the road the existing garage will be demolished to free up space for a complete gut and remodel of the existing home. That will necessarily include the addition of a second floor as we are limited to about 34% coverage on the lot, including any out-buildings. Now if neither my brother nor I choose to move in to this house, we may approach the city about including an attached garage in the remodel but that's a ways off. For now it's really about spending some time with dad.

 

[7th Kahuna]

Just in case you are curious, one of those projects is going to look a bit like this. Same year, all original except the paint and in storage since the 80's. Lots of work needed but not much to recreate other than the shine.

 

[bczygan]

So, you have defined the problem, which also designs the solution. This must be done in stages. More than 2. Design a garage that accommodates working on your present projects with your dad. Perhaps as an addition to the existing garage. Perhaps a cheap or even temporary structure. Maybe built out of panels that can later be reconfigured or reused. Maybe even a structure that you bring in and then move away later. I don't know the exact layout and setbacks and area and height requirements, but you do, so you can meet them. You can build a structure that can be added onto in floor space and even in height, later when the existing garage is demolished and the house is made higher. What you need right now is a space to do specific projects. Design the space so it does just that, but will transform later into the future plan. To do that, start with the ultimate plan and work backwards. Draw up the ultimate plan for the house and garage. Then place the existing garage on the plan and see what part of the ultimate structure can be built now. Maybe it ends up being a large one bay plus shop space. It will be shorter than the ultimate plan, so build it with walls that can be extended vertically later with a roof that can be raised. Maybe the walls will be masonry with a metal roof that can be later jacked up and infill panels installed. Maybe the structure will be steel and additional columns can be added on top of the existing ones later. And when the existing garage is demolished, then additional space or bays can be added on.

What does this starter garage for working on these projects initially need to be? What functions does it have to accommodate. Space for the tools and equipment and the project being worked on. Don't use any of the space for storage of any other project than the one being worked on at the moment. Store everything else elsewhere.

Think of your spaces as changeable and transformable. Can you add a lean to temporary or permanent space to the existing house that can be used for storage now, but other uses later? Can you add a small 2nd story addition now like a cupola, that later will be the stairwell for the 2nd floor, that will give you the height basis for a taller garage now? There are lots of creative ways to solve your needs and match the structure changes to your evolving needs.

Bill (Architectural Designer)

 

[cgv69]

I think this is what your looking for?....

http://www.spancrete.com/markets/residential/

 

[bczygan]

Another thing to think about is this. Make the space where cars and project cars will park 2 story with a lift so you can do a double tier, but with just a slab on grade so no basement below. Build the shop portion of the garage with workbench, machines etc. over a basement that has a dumbwaiter for storage and retrieval and a loft above it for more storage. Certain tools and smaller processes can also go in the basement.

 

[Haywood]

I'm not sure if everything is more expensive in California, but there's no way it would cost $50k for the size you're describing.

The wife and I are building a house with a 2 story garage/spancrete floor like you're describing. I don't have the line item breakdown in front of me, but the entire excavation, foundation, basement walls, basement floor, spancrete, and topcoat for the spancrete was $78,000 and that is for a 1200 sq ft garage and 2200 sq foot house. Going from memory, the spancrete added about $15,000 to the cost vs. doing footings with 4' deep stem walls. The only thing we have going for us is our house is only 10 miles from a spancrete plant so there's not a huge distance for transportation.

Here's a picture for a visual. The walls were just poured last week, spancrete is scheduled to be delivered and installed on the 30th. The garage is in the foreground.

 

[Zeke]

@Haywood, a 20 x 20 single story garage on grade costs 30K in CA.

 

[7th Kahuna]

I think this is what your looking for?....

http://www.spancrete.com/markets/residential/

Thanks, yes, that's the stuff though it looks like it may be the more expensive option. More research to do . . .

 

[7th Kahuna]

Another thing to think about is this. Make the space where cars and project cars will park 2 story with a lift so you can do a double tier, but with just a slab on grade so no basement below. Build the shop portion of the garage with workbench, machines etc. over a basement that has a dumbwaiter for storage and retrieval and a loft above it for more storage. Certain tools and smaller processes can also go in the basement.

Great idea but I think it would require a larger footprint to really be practical. Thanks for the input.

 

[7th Kahuna]

I'm not sure if everything is more expensive in California, but there's no way it would cost $50k for the size you're describing.

The wife and I are building a house with a 2 story garage/spancrete floor like you're describing. I don't have the line item breakdown in front of me, but the entire excavation, foundation, basement walls, basement floor, spancrete, and topcoat for the spancrete was $78,000 and that is for a 1200 sq ft garage and 2200 sq foot house. Going from memory, the spancrete added about $15,000 to the cost vs. doing footings with 4' deep stem walls. The only thing we have going for us is our house is only 10 miles from a spancrete plant so there's not a huge distance for transportation.

Here's a picture for a visual. The walls were just poured last week, spancrete is scheduled to be delivered and installed on the 30th. The garage is in the foreground.

Thanks, that's very helpful. I'll have to play with those numbers a bit. Just to be clear, was that 1200 sf of Spancrete or 3400 sf of Spancrete? Do you have a thread going for your project? Looks like a nice site for a home.

 

[Haywood]

Thanks, that's very helpful. I'll have to play with those numbers a bit. Just to be clear, was that 1200 sf of Spancrete or 3400 sf of Spancrete? Do you have a thread going for your project? Looks like a nice site for a home.

1200 sq feet of spancrete. The spancrete is only in the garage, the rest of the house will be built with regular wood beams and floors.

I don't have a thread going yet, I was going to wait until its a little farther along so I'll have more pictures to post