Placing the Boards
Just about any type of plywood will work.
A few things you need to keep in mind when deciding what type of plywood will work best.
1. How tall is your wall going to be? The taller the wall the more hydraulic pressure there will be on the forms. A thicker plywood or form ply is needed to handle the pressures during the pouring process. Here are some suggestions:
- Walls up to 3′ tall- new and dry 1/2″ plywood
- Walls up to 5′ tall- new and dry 5/8″ plywood
- Walls up to 8′ tall- new and dry 3/4″ plywood, only fill forms half way and wait until concrete has begun to set up before filling the second half.
- Walls over 8′ tall- new and dry 3/4″ plywood, only fill forms 4′ at a time. Wait until concrete has begun to set up before proceeding with the next 4′ lift. Continue this process until you have filled the forms all the way to the top.
Altering the spacing of the Spider Tie stacks so that they are closer together also will increase the performance of your plywood. Most of the time “blow outs” occur because the plywood was is not supported properly. The goal is let the Spider Ties do the work so the plywood doesn’t have to.