Roof Deck Replacement in Sterling Heights, MI

Plywood is cross-laminated veneer, stamped under DOC PS 1, and a roof sheet should show its grade, span rating and bond class (Exposure 1 is fine for roof sheathing, since only the underside sees air). Angi notes it's stronger than OSB and the better pick under heavy roofing. A replaced sheet gets its ends centered on rafters with at least 1/2 inch of bearing, a 1/8-inch gap at every edge and end, and 8d nails about 6 inches apart on the edges and 12 inches in the field. Delamination, where the plies separate and the sheet goes soft, is one clear sign a sheet has to come out.

OSB (oriented strand board, made under DOC PS 2) is the more common deck today because it costs less. For rafters or trusses 24 inches apart, APA rates 7/16 Performance Category sheathing at 24/16. When the panel edges between rafters aren't supported by tongue-and-groove or blocking, APA calls for a panel edge clip, one midway between supports. The small H-shaped clips hold the two panel edges level between rafters so the seam can't dip under a load. Ask whether the quote includes them.

Wood shingles and shakes can go on spaced boards, 1x4s with gaps between them. Asphalt shingles can't: the International Residential Code requires a solidly sheathed deck. If a house started with cedar and was shingled later, check that someone closed those gaps. The fix is to sheath over the boards with plywood or OSB, nailing through to the rafters, not just into the boards. Solid plank decks are different. Lumber sheathing at least 5/8 inch thick on 24-inch rafter spacing meets code, and sound planks can stay.

The eaves and the valleys take the most water on any roof. Ice dams push meltwater back under the shingles at the eaves, an overflowing gutter soaks the edge, and a valley carries the runoff from two slopes. So rot tends to start there. The rotted section gets cut back to the center of the nearest rafters, so the new piece has bearing on both ends, and the fascia behind it gets checked too. Eave rot and recurring ice dams go together, and the ice dam removal page covers the attic side of the problem.

A wavy roof between rafters often points to the sheathing: panels too thin for the span, unclipped edges, or wet sheets that softened. A dip along the ridge or a belly in the middle of a slope points to the framing instead, and new decking alone won't fix that. The IRC lets purlins braced with 2x4s at 45 degrees or steeper shorten a rafter's span, and puts collar ties in the upper third of the attic, no more than 4 feet apart. The code also requires the framing to carry the new roof and the loads during installation. A sag means a framing check before re-roofing.