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We are about to start a new foundation and wanted to know the correct tie spacing for our plywood. We are using 5/8 which we will later use to sheet our walls. I was thinking on a row of ties at 8 inches from the footing and every 16 inches after that vertically. Horizontally I was going to use 2 foot centers. Your input would be appreciated. We are using burke brackets and strong backs if that helps.
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How tall are your walls? How thick?
*Whoops...forgot to say that the walls are 8 inch and between 6 to 8 feet . The footings are being poured first .Thanks
*Is the plywood 5 ply CDX? How accessible is the pour? Are you gonna have to soup up your mud to pour it, or are you gonna stay around a 4+1/2 to 5 slump? You gonna add plasticisers to make it flow? You plan to pump it? You gonna vibrate it? What are you gonna do?
*Are you going to use strip easy ties or are you going to use snap ties. Are you going to use johnny clamps (single waler). I finished a 4' high wall using snap ties. Plywood was drilled the standard 8", 16" ect. We used single waler system but didn't put a tie in every hole. Corners were three ties, next row single middle tie, next row top and bottom tie, next row single tie ect. It worked fine. 6 or 8' use every hole especially if you use strip easy. Don't use OSB plywood or you will be cleaning up concrete.
*Jeff,Your 5/8 plywood in not meant to be used as concrete forms so you will have to take special care.Nail a 2x4 plate to the footing on both sides of the form. Use 3 1/2 common nails, predrill and nail in place with a small 5" piece of tie wire inserted in the hole. This will make removal easier.Place your first row of ties at 8", the second at 12" further and the rest at 16". Use one row at the top about 2 inches below the top of the concrete. This will ensure that you can keep your lines fairly straight and prevent your walls from being too irregular and wavy.May seem like a lot of tie lines but I don't know how experienced you are with concrete and I'd hate to see you post about what to do when your forms blow.good luckGabe
*I used OSB once for a small addition and whaled the crap out of it. It sure made for an interesting pattern where the rough side was facing the concrete. Afterwards I got to thinkin' it would make kind of a nice basement wall. The pieces of OSB I used did get awfully soft though.
*With tall walls (over 6 feet high) our guys normally build 2X4 walls (5/8 ply works fine) with the plywood facing in. Our studs are spaced 2 foot OC. We would attach 3 whalers to this wall; one 7 to 10 inches off the ground, one about dead center, and the top one about 12 inches down. On a tall wall, the "push" is going to be very low.Our whalers are doubled 2X4s on edge. Sometimes we install 1/4 inch luan scrap pieces between the 2X4s to give us enough room to install "pencil rods" which run through small holes drilled in the plywood. The rods are tightened off with square headed bolts that we refer to as "catheads."Even with the use of the pencil rods and the whalers and stiff-backs; we still run wood bracing (if possible) about every 2 foot. One brace is attached to the top whaler and angles back to the ground. Another brace is attached directly to the bottom whaler and trails back also. Both braces are nailed together and held in place by a stake driven behind them.I know guys will say this is overkill, but there is tremendous push on these walls with the concrete. If a wall of this height blows out, your gonna lose the whole pour; no question about it. I can't emphasise enough to make sure the base of your forms are braced off well. Also, make sure your corners are locked in properly with your whalers. If your gonna have trouble, the bottom half or the corners are most likely where it will occur.An easier way to form these walls would be to rent Simon panels that are locked in place with wedge bolts. You still have to use whalers and (in this case) snap ties. Waco scaffolding rents these forms. They are lightweight and go up fast. Level a 2X4 sill plate and then attach your first row of panels to this. It helps keep the panels level and in line.Good luck on your project.Davo.
*Jeff,You'll want to have a controlled pour rate. If you poured at 2ft/hr for example, the concrete pressure would be about 410psf and your 5/8ths with 16" OC ties would be at about 1/2 it's ultimate strength. If you filled the forms to 6ft all at once it would definately blow out. 3/4 plywood gives you 50% more strength and 8x3/4 snap ties are sized for this application.