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I am hiring block masons to build me a 24' x 44' block building, and I want to know how to keep the lower courses of blocks from bowing under pressure of 3 feet of dirt backfill or weight from the roof. I had to get another block mason since the first one I hired was no good; the second mason did not take down the five courses completed by the first mason, but rather continued to build from there. Now, I am concerned that the wall could blow out. How can I prevent that?

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Blocks are very strong under compression from above, so if the walls are bowing under the weight of each course of blocks, that makes me think the walls are not plumb. You would need to tear down the walls and redo them to be plumb.

You say you want your walls to "withstand the pressure of the dirt." Are you burying the structure? Correctly-built block walls may be strong under compression, but they are weaker under pressure from the side. Tread very carefully. It sounds like you may want to involve the services of a masonry professional if you're not sure how to build a block wall in such a manner as to prevent it from collapsing under whatever loads you're putting it under. Built correctly, block walls are very strong. These blocks are resting on a concrete foundation, right? Ideally you would have a concrete foundation with rebar sticking out of it that you would place the blocks over such that the rebar goes through their cores, and then you would grout or concrete the cores to tie the blocks into the foundation. Block walls are very heavy. Without an adequate foundation, the structure is doomed from the start.

If your block walls are not straight, plumb, and tied into an adequate foundation, you'll need to redo them so that they are--end of story. If all of that is fine, there are a couple of ways you can reinforce your block walls to increase their resistance to exterior pressure from a bunch of dirt:

  1. Put rebar through the cores and pour concrete in them.
  2. Apply a layer of surface-bonding cement to both sides of the wall.

Do both, and the wall will probably outlast your great-grandchildren.

But again, I would strongly recommend hiring a professional to help you. You don't want to build a structure that's unsafe. Masonry is heavy. If it collapses when someone's inside it, that person is probably a goner.

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To prevent water pressure, buried block walls should have a perimeter drain and gravel backfill on the outside of the wall. If it's so structurally unsound that it can't support the roof, tear it down and start from scratch with a reputable builder that knows how to reinforce cinder-block walls. Retrofitting a masonry wall, especially in earthquake country is going to end badly, no matter what you do. Soft courses that low in the layer will never go away (or rather will in the first good quake fail spectacularly). –  Fiasco Labs Jun 15 at 17:58
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Yes, it would help if you described what exactly is wrong with the bottom courses. Fiasco is right. If they're unsound, no amount of reinforcement is gonna help; you'd need to start from scratch and get it done right from step 1. –  iLikeDirt Jun 15 at 18:17
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I am also concerned because he cut my rebar and the footer is not really tied into the block. Where in the world is this located? –  Fiasco Labs Jun 16 at 0:03
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Do you have a permit for this structure? If so, there should be engineering stamps and approval by the permitting office. If they and the inspector are OK with everything, then you should be fine. If there is no permit, then you may want to re think things. –  DA01 Jun 16 at 2:04
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UPDATE - I have put 1/2" x 10' rebar in each block core and filled it completely with concrete. The building is 24x44 and 19 courses high, so I do believe it will not blow out. Thank you everyone for all your help!! –  Tina Jun 20 at 18:47

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