What do the GAF Timberline HDZ installation instructions require?
Where to find the official version
Search GAF's document library by product name, or read the abbreviated version printed on each bundle. Work from the document for your exact product, because Timberline HDZ, UHDZ and older Timberline lines differ in details, and manufacturers revise their instructions over time.
The requirements that matter most
- Deck: solid, dry sheathing. Shingles cannot go over spaced boards.
- Slope: 2:12 minimum. Between 2:12 and 4:12 the instructions call for added underlayment protection, and many crews use a full leak barrier there.
- Starter: starter strips along eaves and rakes so the first course has a sealant line beneath it.
- Exposure: 5 5/8 inches per course on Timberline HDZ.
- Nails: roofing nails with at least a 3/8 inch head, long enough to go 3/4 inch into the deck or through it, driven flush in the StrikeZone. Four per shingle is the standard; very steep slopes require more nails plus hand sealing.
- Stagger: offset joints from course to course by at least the minimum shown in the instructions.
Why the details carry money
GAF's enhanced warranties depend on qualifying GAF accessories, such as starter, ridge cap and leak barrier, and on installation by a certified contractor who registers the roof. A Timberline roof put on with off-brand accessories or sloppy nailing may keep water out for a while, but it can lose warranty coverage that would otherwise apply. Read roofing warranties explained before you sign, and see architectural vs 3-tab shingles for how Timberline compares with older styles.