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dmj245 01-24-2006 10:42 PM

Building garage with elevated concrete floor
I have a 34' wide by 28' deep 10' high concrete block foundation attached to my home. It is my intentions to pour an elevated concrete floor at the 10' mark, and utilize the lower protion of this structure for storage etc.
The garage being built above, will house three vehicles above the storage area, have a 7-12 pitch roof with its own intended storage. The footer holding this whole thing is 5' wide by 1' thick reinforced with extra rebar. (I know it looks like a sidewalk, :eek: but the ground was soft at the time of construction, so support was a concern. We decided to make it a float footer)

I am having a problem analyzing what will be needed to support the concrete floor, the design of the support structure holding the floor and of course tying the whoile business into cost.

I am not concerned very much about the loss of storage space below the garage since that can be delt with by altering what I store there. The structure needs to be strong enough to support the weight of two 3/4 ton pick-up trucks and a full size family car - plus work bench, tool bins and other minor items commonly found in a garage.

I am open to suggestions, drawings, ideas, or anything else anyone can come up with. I need in-put bad!

Bonus 01-25-2006 09:51 AM

With all due respect, this is a job for an engineer, you're going to need one at some point so you might as well get one in at the beginning. Love to hear about it, though, if you're interested in sharing your project. :)

dmj245 01-25-2006 07:36 PM

Yeah ... I know if I want to do it right I should consult with an expert, and I will probably do that soon.

Keeping in mind that I am obviously NOT an Structural Engineer, I thought that I could utilize my wide foundation (remember it's 5' wide by 1' thick with additional rebar for strength) which is of equal distance on both sides of the concrete wall. I have a friend who can get me all the used Steel I-Beams I want as long as I want to cut them and weld them for sizing. He suggested a "spider" type of structure. Beams in each corner from the foundation up to the pour level. Additional beams along the long walls at equal spacing, and perhaps at least one ot two along the short walls, all firmly placed on the footer extending upward to the pour level. Then I could somehow box them in framing the support for the concrete floor which will be poured into Q-Decking. Of course when I'm done it will probably hold 100 tons and cost 100 thousand dollars in labor and transport of materials.

What I'n looking for is something that can span the 34" distance, with support if needed in the center like a column but it has to be able to hold the weight of the poured concrete floor and three vehicles etc., as I said in my original thread. The idea above is just simple over-kill on designing a structure.:eek:

Thanks for your in-put, I will continue to search for ideas, and will post (for eveybody's amusment) how I solve this business ... However I am still open to suggestions from anyone who's interested. :)

Bonus 01-25-2006 07:47 PM

Yeah, I'm afraid it's beyond my comfort zone to design stuff that holds up vehicles over someone's head, but I hope you do keep us posted. :)

jmic 01-25-2006 08:31 PM

Try to Google "concrete planks" Engineered pre-stressed concrete decking.

dmj245 01-26-2006 01:44 PM

Okay Joe! Thanks I'll do that. And I agree with you "jmic" This is why I want it to be strong. The thought of me working under the garage with all that tonnage above...

If you guys would like, I have a few very good quality digital pictures that might make it a little easier to see what I have to deal with, logistic-wise that is.

I'll see if I can get them loaded up online tonight

dmj245 01-26-2006 02:37 PM

Disregard the photo idea. Since it's digital, all my pictures of the foundation are 2.7 to 3 megs. To big to download onto this system.

JasonRieke 04-20-2006 10:06 AM

Do you have a problem with a center row of columns? Basically would have 17' between the wall and the center column down the middle of the storage space?

Are the walls on the sides of the space already finished or is this still in the planning phase with no construction (besides the footing) being poured?

Darylh 04-20-2006 11:27 PM


Originally Posted by dmj245
Disregard the photo idea. Since it's digital, all my pictures of the foundation are 2.7 to 3 megs. To big to download onto this system.

Go this web site and download this free program You can down size your photo and its easy to learn

dmj245 04-21-2006 11:13 AM

Building a garage w/elevated concrete floor
Yes, the 10 foot high foundation block walls on the three sides are up and it is fully enclosed (the fourth wall is the basement wall on the side of the house). All of the block walls, house and garage, sit centered on a 5 foot wide by 1 foot thick reenforced footer, ("floating footer" I believe is the term - I was concerned at the time of initial construction about some soft ground around the foundation, so I beefed it up, however that is not a concern anymore.) The ground floor of what will be the lower part of the garage is undisturbed dirt at the moment, but I can dig and pour an additional foundation to support any additional collumns or walls that may be needed. I will leave it flat and covered with gravel rather than cement when I'm done. I don't plan on working in this area, just storage.

What I'm trying to do is use the bottom part of the garage for storage of summer equipment (lawn tractor, tiller, motorcycles, etc) in the winter, and vice-versa with the winter equipment (snow plow, snowmobile, etc) in the summer. This way I won't have all this stuff "upstairs" in the garage, just the stuff I'm using at the time. It is my intention to cut about a 6 foot wide doorway on the rear wall for access to the storage area. I do not want to access the storage area from the house basement. I want to keep the house foundation sealed. Access to the storage area from outside is fine.

At the time that the walls were built the intention was to just fill everything in with dirt and rock, build the garage over it all and landscape the dirt and yard on the outer walls. This is why there was no access door put in the back wall.

Keep in mind that what ever configuration I build regarding this storage area, it has to hold the weight of two full size cars and my 4X4 pick-up truck overhead. I don't have a problem using additional support for peace of mind. I have no engineering background so support and load security is paramount.

Any more questions or suggestions please feel free to contact me...
Thanks for your help and interest in this project.



crecore 04-24-2006 07:40 AM

It can be done, will be pricey. Definately need an engineers stamp on this one! Your footings seem ample, but an engineer will determine this based on loads and soil. The real questions is how you can tie the floor into the existing walls. Are you setting on top like the drawings some showed? There's no way you can lag a ledger of any kind onto that wall and support that load. Worse comes to worse you could pour new footings and build a wall inside the wall (or columns) or notch and beam perhaps.

Consider that the beam web structure not only has to hold the weight of itself, the concrete and the vehicles with a safety factor.... but it also has to seal and support the weight of the concrete wet !!! I have been involved in a dozen pours of various difficulties, some quite large, but the precast floor sounds like it may be the way to go on this one... even though I know nothing about them!

Good luck... interesting project.

johnlvs2run 05-05-2006 10:49 AM


Originally Posted by Bonus
Yeah, I'm afraid it's beyond my comfort zone to design stuff that holds up vehicles over someone's head, but I hope you do keep us posted. :)

Same here.. It makes me cringe just reading about this, and I would certainly never buy a house with this type of construction.

Why not keep the vehicles on the ground, and build the storage area above them, especially since you're not going to be using it much.

JasonRieke 05-11-2006 08:59 AM

If it is properly constructed you really shouldn't have any problems. You guys have to realize that there are a bunch of parking garages in this world ;) . It can be done...just do it right...get a structural engineer.

What have I done 05-31-2006 04:13 AM

i dont see the problem here. In the midwest most of us have "capped garages" I have a 26x26 garage on top of a basement 26x26 garage. Most are using "flex-core" for the upper garage floor and pooring a 2" floor overtop of that.

Mine was poured on site. I believe it is 10" thick. lots of rebar. When it was poured about 100 2x pillars were placed under 3/4" plywood. the rebar was tied above the plywood framing.
We left the pillars in place for 1 month while the concrete cured. my 2 daily driven cars park side by side while my camaro is turned sideways and stored at the front of the upper garage. the lower garage stores the classic cars and lawnmower.
most houses in our area have the capped garages, so its fairly common

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