Roof Deck Applications
A. EXISTING DECK AFTER TEAR OFF:

1. Deck must be clean and all nails must be removed or knocked down flush with the surface.

2. Defective or rotted decking must be replaced. The new decking should match the existing and be nailed in the same manner.

3. New decking exposed to the exterior of the building should be painted with a good primer.

B. FILL IN OF SPACED SHEATHING BOARDS:

1. Fill in is not allowed for any composition roofing product.

2. Fill in is allowed for most other types of roofing.

3. Fill in spacing is not critical except where required to meet specified nailing requirements for that particular roofing system.

4. All fill in boards should end on rafters and be attached with two fasteners per rafter location.
Fill in spaced sheathing to create an adequate nailing surface for specific roofing materials. This surface was used in applying cementious materials; it would not be suitable for a composition roof application which requires plywood decking.
 

C. PLYWOOD OVER SPACED SHEATHING:

1. New material shall be minimum 3/8” exterior grade plywood or oriented strand board (OSB). IRCC recommends minimum 7/16” OSB or 15/32” CDX plywood.

2. Plywood vertical seams are not required to end on rafters.

3. Horizontal seams shall be fully blocked with spaced sheathing boards or fill in boards.

4. All fasteners shall be 1 1/2” minimum length. Staples or nails may be used.

5. Fasteners shall be placed approximately 6” apart along all horizontal edges.

6. Fasteners shall be placed along the vertical edges over each spaced sheathing board. One minimum per location.

7. At least two rows of fasteners shall be placed 12” apart over spaced sheathing boards roughly equidistant from the top and bottom edges of the plywood or OSB.

8. All exposed edges of plywood or OSB shall be covered with edge metal or trim board.

D. PLYWOOD FOR STRUCTURAL SUPPORT:

1. For structural support and/or new diaphragm, there should be engineering for nail type and pattern.

2. Where plywood is installed to meet fire code requirements for combined deck and roof applications, refer to building codes, manufacturer’s specifications or other design professionals.

E. BUILDING DEPARTMENT INSPECTIONS:

1. Dedicated tear off and plywood nailing inspections are not recommended. Spot checks of the roof deck and plywood nailing should be done during an in-progress inspection.