Bond Beam Basics
Last week I also got started cutting the block for my bond beam. You can buy “bond beam block” already cut to roughly this shape, but those block have solid bottoms, so there would be no way for the vertical rebar to enter the bond beam. So, I had to make my own.
These modified block are pretty easy to make. It just takes two cuts with the diamond blade, a hammer, a chisel (known as a “brick set”) and a little elbow grease. So far I have 16 of them cut (and about 80 more to go). In pic 1, the two yellow lines represent where the horizontal rebar will lay (though I may only use one piece of rebar).
There is one little problem to solve with this home-made block design. See pic 2. I want all of the bond beam block to be filled with concrete. I also want concrete in all the cells that contain the vertical rebar. but no concrete in the adjacent cells that don’t have vertical rebar. So, I have to put something in to block the concrete from falling through and going down into the cells where I don’t want it. I have read about stuffing the tops of those cells with newspaper to block the concrete, but I don’t like that idea. I have also heard about putting window screen material in between the block to act as a dam. I don’t think the screen would be strong enough to hold the concrete while it cured, but I suppose I could make up a test piece and concrete up a test block to see how it works.
I am also considering using thin metal sheets made out of the metal found in “trim rolls” that some siding people use to make metal trim for soffits and around windows and doors. The material has to be thin so it won’t raise the top of the block above my desired elevation. I’m not locked in to this trim roll approach; I’m still open to suggestion. Anybody got any ideas?
These modified block are pretty easy to make. It just takes two cuts with the diamond blade, a hammer, a chisel (known as a “brick set”) and a little elbow grease. So far I have 16 of them cut (and about 80 more to go). In pic 1, the two yellow lines represent where the horizontal rebar will lay (though I may only use one piece of rebar).
There is one little problem to solve with this home-made block design. See pic 2. I want all of the bond beam block to be filled with concrete. I also want concrete in all the cells that contain the vertical rebar. but no concrete in the adjacent cells that don’t have vertical rebar. So, I have to put something in to block the concrete from falling through and going down into the cells where I don’t want it. I have read about stuffing the tops of those cells with newspaper to block the concrete, but I don’t like that idea. I have also heard about putting window screen material in between the block to act as a dam. I don’t think the screen would be strong enough to hold the concrete while it cured, but I suppose I could make up a test piece and concrete up a test block to see how it works.
I am also considering using thin metal sheets made out of the metal found in “trim rolls” that some siding people use to make metal trim for soffits and around windows and doors. The material has to be thin so it won’t raise the top of the block above my desired elevation. I’m not locked in to this trim roll approach; I’m still open to suggestion. Anybody got any ideas?
The window screen material would probably be a lot cheaper than the metal pieces, as well as being lots easier to cut and handle.
posted by Tony @ 7:52 AM
4 Comments:
Great idea on the bond beam to integrate it into the wall. Does it take long to break the tabs out? On keeping the concrete out of the voids that don't need filled, do you think you'd be able to use something link binding strap steel (like used to hold a load of blocks or lumber together, as a bridge covered in tarpaper? Maybe some coorugated plastic, like used in election and cigarette signs? I'm just brainstorming here, not knowing how much weight or how you're going to pour it. If you have a home recylcers around, it may be worth a look around. We have one here, and often they'll have old laminate sheets, outdated patterns or plastic wall board that suppliers donate for the write-off.
That is a lot of weight that is going to be on the two voids in the middle. I've poured a lot of concrete and it always takes more to support it that you think. I'm guessing window screen or even flashing is a no unless you have some way of supporting it in the middle of the void. Even with a block setting on top of it, unless you had a way to prevent it from pulling out, I would think it would sag into the void. I would probably use a piece of quarter inch plywood to lay across the openings of the two non-filled voids from the top of the bond beam which would decrease the thickness of the bond beam in that area by 1/4". I'm not sure if this is acceptable. Maybe if you creased the metal flashing so that ninety degree bends and a flange overhung on each side of the wall it might work. Make it harder for the weight of the concrete to pull it through the seam.
Thanks for the comments guys. I guess I'll make a test pour to see how the metal and screen hold up.
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