- 1). Install the seal plate on top of the foundation wall. The sill plate must be treated and at least 8 inches wide. Your foundation walls will be fitted with anchor bolts that must be inserted through the sill plates; however, if the bolts are not in place--set into the foundation concrete--then you may drill your own using a hammer drill and 1/2-inch concrete bit. Make sure that all anchor bolts are tightened snugly.
- 2). Install two rim joists. Your foundation will have four sides, so you will need to install two of the four rim joists to form a 90-degree angle. The rim joists will be the same materials as the floor joists. For example, if your floor joists are two-by-tens, then your rim joists will be two-by-tens. The rim joists are installed, edge up, along the outermost edge of the foundation sill plate--treated two-by-eights that are anchored to the foundation.
Install the rim joists by attaching them together at the corners where they meet, then toe nail them into the sill plate every 12 inches, and then attach rim ties--galvanized metal ties--every 16 inches to hold them securely to the sill plate. - 3). Pull a tape measure from the corner beginning on the longest side of the rim joist, and mark off 12-inch or 16-inch increments. This will be your center mark for your floor joists. Drop back 3/4-inch to the left of each mark and place another mark. This is where the edge of your floor joist will align.
- 4). Mark your floor joists to the exact width of the foundation and subtract 3 inches from that measurement to allow for the thickness of two rims joists--located on each end of the floor joists. The floor joists will run across the foundation's shortest span. If your foundation is 20 feet by 40 feet, then your floor joists will be 19 feet 9 inches--subtract 3 inches from 20 feet to allow for the two 1.5-inch rim joists. Attach the floor joists to the rim joists with 16 penny nails after you have aligned them with the center marks placed on the rim joists.
- 5
Staggered Plywood JointKnotty Floor image by Towards Ithaca from Fotolia.com
Attach the remaining rim joists--opposite corner--to the floor joists and attach them at the corners. Check the floor and make sure that it is square by pulling a tape measure across opposite corners; the distance of the corresponding corners should be the same.
Attach 3/4-inch plywood to the floors by running the plywood perpendicular to the floor joists. Begin in one corner of the floor and apply construction adhesive to the floor joists before you lay down the plywood. Continue one row of plywood from one corner to the next, and then stagger the next row of plywood. (See the staggered joint in the attached photo. Attach the plywood with 8 penny nails that are spaced 12 to 16 inches apart.
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