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Old 10-22-2008, 05:51 PM   #1
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CMU Garage Walls

I have an existing slab 35' x 50' (24" or 36" interior and perimeter beams).

Anyone have access to codes to determine requirements for foundations under 20' high CMU exterior walls in Texas? Or perhaps a better question, how high can I go? Soil is crushed limestone at least four feet deep based on nearby perk holes.

Also understand that I should horizontally reinforce every other layer and vertically reinforce every 24" (no more than 12" from corners). Yes? If so what # rebar and does that rebar need to be continuous? Slab will need to be drilled. I assume this works with epoxy bonding. Yes, no?

How about expansion joints? Have looked at other projects and see either no or 30' OC joints.

Thanks in advance.


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Old 10-22-2008, 06:19 PM   #2
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You need professional help. Find an engineer.

You never mentioned what thickness of block you are using. That is critical for tall walls. 12" thick block will be the cheapest.

The joint reinforcement (every other course) you suggested is normal.

The amount of vertical steel will depend on what the engineer determines. Thick walls can use less steel and grout. If you are in Galvaston, you could be looking at a different building than something way inland in Texas.

You should also find out if your slab/footing AND soil is adequate. Just because someone guessed and built it does not mean it is right.

When you get to 20' high walls and are trying to do it yourself with little knowledge, you are taking a big risk and need some help, even if you just call it a garage. Once you get the wall up, you get into the danger zone unless you have it braced until you can get some beams or trusses on it. It take very little wind in the middle of the night to dump an unbraced 20' high wall.

Do you have access to equipment to get the block up that high or are you relying on cheap labor to climb the ladders with block, mortar and grout? In that case, you will be slow and have greater need for a proper design and bracing until you can get someting on top to hold the walls together or apart.



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Old 10-23-2008, 03:32 AM   #3
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why not use insulated conc forms ? ? ? you'll still have the same concern w/footer, tho.
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Old 10-23-2008, 11:46 PM   #4
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As a structural engineer I would recommend you find a local structural engineer. He or she can do an analysis to determine the capacity of your current foundation system, and design the garage walls and roof diaphragm. With masonry you're going to need the engineer to a decent amount of detailing (construction drawings) for control joints, lintels above openings, connection of roof to wall, etc.

Do you have any drawings or details pertaining to your existing slab? If it is not properly reinforced you could actually crush your grade need a structural engineer to come out and look at it.
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Old 10-28-2008, 06:37 PM   #5
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Thanks guys....

I've already got an engineer scheduled to take a look but wanted to hear back from Dick, who I just knew would respond. Wildcat was a bonus. I've read many of your posts and respect your views.

yesitsconcrete, I've loved that technique since I saw it several years ago, but don't know that anyone in my area understands it. There are so many masons here in Texas, that I had to go the block route on this project.

FYI, I found the plans I drew up for the foundation. Beams are 12" into crushed limestone and extend roughly 12-18" above new grade. New grade was created after we bulldozed the 6-24" of clay topsoil completely away exposing all the natural limestone. Beams are 10' on center down the fifty foot length with one beam in the middle of the 35 foot width. All #4 rebar cages in the beams with #4 grid over the top, 5" minimum thickness concrete (all 4000-5000psi?) between beams. Poured in 2002 with no real cracks to speak of today.

I'll keep you posted.
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