This document establishes that the repair cannot be confined to the damaged area. The code-evaluation report for GAF’s synthetic underlayments: minimum 3″ head laps and 6″ end laps, applied in shingle fashion. Restoring code-compliant laps after damage means replacing whole runs, not squares.
System requirement GAF · Roofing · 2022 · 2 pages
ICC-ES Evaluation Report ESR-2808
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ICC-ES Evaluation Report ESR-2808
Issued by GAF. Published here complete — no summary standing in for the document, no email required.
Issued by GAF. Held in this firm’s reference library; not published elsewhere. Homeowner-identifying details, where a letter was addressed to a particular property, are blacked out — nothing else is altered, and no operative text is ever redacted.
What to do with it
A roof or a wall is an assembly, not a surface. When the manufacturer requires underlayment to lap onto the neighbouring slope, or the water barrier behind siding to be continuous and taped, the damaged area cannot be treated in isolation — and an estimate that prices it that way is describing something that cannot actually be built.
- You have the manufacturer’s document. That part is finished. Most homeowners never get this far, and it is the step a carrier cannot argue with — it is not your opinion, it is the company that made the product.
- Put it in writing, to the adjuster, with the claim number. Attach the document and ask one specific question: name the exact replacement product — manufacturer, line, colour, dimensions, exposure, nail zone, sealant design, supplier, quantity available locally — and who will answer for the repair if it fails. Vague answers are the whole game; a specific question ends it.
- Get the position on the record before anything gets installed. Once a mismatched or incompatible repair is on the building, you are arguing about something already done.
If you want the second and third steps handled by someone who does this for a living, that is what we are for — and the review costs nothing. If you would rather do it yourself, the document above is yours either way. That is the point of publishing it.
Related documents
Other GAF documents
GAF Timberline HD
The most-installed architectural shingle in America, discontinued July 1, 2020 across every U.S. sales area and every colour, effective immediately. The stated alternative, Timberline HDZ, is a different product — see the do-not-mix letter below.
GAF Timberline HD vs. Timberline HDZ
The companion to the discontinuation notice, and the one that closes the loop: the successor product cannot be used to patch the old one. GAF withdraws warranty coverage where the two are mixed.
GAF Timberline HDZ
The obvious workaround — trim a modern shingle down to the old dimensions — is one GAF specifically rejects, because cut shingles may not seal to one another.
GAF Timberline UHD
Discontinued March 6, 2023 in all sales areas — and the notice forecloses the substitute in the same breath.
GAF Grand Slate · Grand Slate II
Discontinued in all colours effective March 25, 2013, with GAF acknowledging that no exact replacement product exists.
GAF Capstone Lifetime Designer
Discontinued February 2012 with no remaining supply channel — confirmed by GAF’s Director of Timberline HD & Designer Shingles.
Other manufacturers saying the same thing
CertainTeed asphalt shingles
The code-evaluation report treats a CertainTeed shingle roof as a complete system — compliant underlayment, the specified starter, hip-and-ridge accessories, and fasteners meeting ASTM F1667. A repair that substitutes non-conforming components does not just look different; it falls outside the report and can forfeit the Class A fire classification.
CertainTeed valleys, walls and chimneys
Open valleys are required for Custom Lok 25 and strongly recommended for Grand Manor, Carriage House, Centennial Slate, Landmark TL, Presidential Shake and Presidential TL — their thickness and multi-layer construction are not designed to bend into a valley. A closed-cut or woven valley repair on those products is contrary to the manufacturer’s own manual.
CertainTeed roof deck spacing
Deck board spacing requirements beneath a CertainTeed roof. Where the existing deck does not meet them, the fix is not confined to the shingles.
CertainTeed vinyl and polymer siding
Vinyl siding is hung, not fixed: nails are centred in elongated slots and driven loose, leaving roughly 1/16″–1/8″ of play so the panel can move with temperature. CertainTeed states that deviating from its requirements voids warranty coverage, and that failing to establish a smooth, solid substrate is itself a misapplication.
The rule this document serves
Your policy promises repair or replacement with material of like kind and quality. That is a replacement-cost and indemnity obligation, not an appearance theory — and it is why “matching” is the carrier’s word, not the policy’s. Where the installed product cannot be bought, or cannot be combined with what is still sold, the covered building cannot be restored to like kind and quality by patching it, and that is true before anyone argues about how it looks. The full doctrine, and the other 125 documents, are on the discontinued materials hub.
You have the manufacturer's document. The next part is the argument. Handing a carrier a technical bulletin and getting it honoured are two different jobs. The case review is free, and you pay nothing unless we recover.
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