To prevent your house from falling off its foundation during an earthquake.

Materials Needed	Tools Needed
1/2" structural I or C-DX plywood 8d Common or Sinker Nails 16d Common or Sinker Nails	Circular Saw Jig Saw 1-1/2" Hole Saw Framing Square Chalk Line Hammer Pencil Tape Measure

1. Check the sill plate to be sure it has been adequately bolted to the foundation.

2. Check to be sure the sill plate and studs are the same dimensions (flush at face). If not, block between the studs and nail the blocks into the sill plate with six 16d nails per block to create a flush nailing surface for the plywood.

3. Measure the distance between the bottom of the sill plate and the top of the top plate. Measure the distance between the comer stud and the middle of a stud at 4' or 8' away to be sure a standard sheet will fit; if not, two sides of the 4' x 8' sheet will need to be cut. Check that the studs are square with framing square and use it to lay out cuts on the plywood.

4. Mark the center line of the vertical studs on foundation and above cripple wall to locate studs behind plywood for later nailing.

5. Locate all exterior ventilation grates with respect to some easy reference point so that they will not be covered with plywood.

6. Cut the plywood with a circular saw using a plywood blade.

7. Place each pre-cut section of plywood up to check fit. It may need to be trimmed; a jig saw can be used to trim the plywood without taking it out of the crawl space.

8. Tack the plywood up temporarily with a few nails. Using chalk line, snap a line on the plywood between the marks made in Step 4. Nail the plywood to studs and plates with 8d nails. The nails should be spaced 3" apart around the entire perimeter of each plywood panel and 6" apart in the middle of each sheet.

9. Measure and cut out a space with the same dimensions as the ventilation grates previously located using the jig saw.

10. Using a hole saw, drill two 1-1/2" ventilation holes for each cavity between studs. The holes should be 2" up from the sill plate, 2" down from the top plate and centered between the studs.

11. Measure the next section to be cut and fit only after the previous section has been completely attached.

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