Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
GAF Home Additions & ADU: The Houston Owner’s Guide
GAF home additions and ADU projects in Houston typically run $45,000 to $130,000 for a permitted, code-compliant addition, with detached ADUs landing between $90,000 and $220,000 depending on foundation work, utility runs, and finish level. Our crews frame, sheath, and roof these additions using GAF roofing systems matched to your existing roofline, so the new structure sheds water the way the rest of the house does. Most homeowners call us because a previous addition is leaking at the tie-in, the roof flashing has pulled away from the house, or they are planning an ADU and want the roofing spec locked down before the first wall goes up. We are an independent remodeling contractor, not affiliated with GAF, but we install their systems on additions and ADUs across Houston every year.
Which GAF Models This Applies To
For a home addition or ADU, the GAF decision is less about a single model and more about matching your existing roof assembly. If your house wears GAF Timberline HDZ or Ultra HDZ shingles, the addition should carry the same series so the roofline reads as one continuous plane rather than a patch job. GAF Timberline shingles come in slightly different exposure widths by series, and a mismatched shingle line is visible from the street even when the color is close. The critical compatibility point is the underlayment system: GAF Deck-Armor and StormGuard form a two-layer assembly, and skipping StormGuard along the tie-in valley or at the addition’s eaves is how a Houston addition becomes a leak liability within two or three years. We also install GAF TPO on flat-roof ADUs here in Houston, where a low-slope membrane handles pooling water and AC-condenser runoff better than shingle systems ever will. If you cannot identify the exact GAF shingle on your house, pull a photo of the roof from the street and we will identify it during the estimate walkthrough.
Styles & brands we work with
Signs Your GAF Home Addition or ADU Is Failing
- Water staining at the ceiling where the addition meets the original house. This is the classic tie-in failure. The flashing detail between old and new roof planes was either under-built or installed without StormGuard at the valley, and Houston’s afternoon downpours find the gap quickly.
- Shingle blistering or granule loss on an addition that is less than five years old. Additions with poor attic ventilation trap heat directly under the roof deck. A GAF roof needs balanced intake and exhaust airflow; without it, shingles cook from below and fail early.
- Buckling or lifted shingle edges at the eaves of a flat-roof ADU. TPO membranes expand and contract hard in Houston’s summer heat. If the termination bar or fascia detail was fastened poorly, the membrane pulls free and wind gets under the edge.
- Daylight visible through the roof deck inside an unfinished ADU attic. This means the underlayment installation skipped fasteners or was torn during shingle install. It will leak; the only question is when.
- Nails backing out on a metal drip edge or ridge cap after a heavy storm. Houston’s wind-driven rain exploits every loose fastener. GAF ridge caps and drip edges installed out of spec lift at the nail line and let water walk sideways into the roof assembly.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
For a GAF-spec addition or ADU project in Houston, plan on $45,000 to $130,000 for the full scope, with detached ADUs at $90,000 to $220,000 once foundation, electrical service, plumbing runs, and interior finishes are counted. A roof repair or tie-in correction on an existing addition runs lower: $400 to $1,800 for targeted flashing, membrane, or shingle repairs, and $8,000 to $20,000 for a full reroof of the addition using GAF materials. The range comes down to square footage, roof slope, whether decking needs replacement, and how much of the tie-in detail must be rebuilt. Every quote includes the roofing underlayment, shingles or TPO, fasteners, flashing, trim, and permits where required by the City of Houston. We write the price before any work starts, and the 365-Day Done Right Promise covers the finished project. If it is not done right, we make it right.
DIY or Call Us?
If you are planning an addition or ADU, the parts you can safely check yourself are limited to what you can see from the ground: missing or damaged shingles, visible flashing gaps, daylight at the eaves, or granules collecting in the gutters after storms. Anything involving the roof plane itself, especially the tie-in between an addition and an existing house, is not a weekend repair. The flashing, underlayment, and ventilation details are the difference between a dry room and a Houston mold problem. Roof work at height is genuinely dangerous, and a tie-in failure is not something a homeowner should chase with a caulk gun. We also handle the KraftMaid cabinets, Cambria and Silestone countertops, and finishes that go inside the addition, which means one written scope instead of three contractors. Call (254) 272-5240 and we will walk the roof with you.
FAQs
A properly installed GAF Timberline roof on a Houston addition or ADU should last 25 to 30 years, but the tie-in flashing at the existing house is the first component to watch, often needing attention around year 10 or 12 in Houston’s storm cycles. Call (254) 272-5240 and we can inspect your specific tie-in detail.
If the failure is at the flashing, a valley, or a single membrane seam, a targeted repair at $400 to $1,800 usually solves it. If the sheathing underneath is compromised or the original underlayment was skipped entirely, a full reroof of the addition is the honest fix. Call (254) 272-5240 for a written assessment.
A permitted ADU typically takes 4 to 8 months from foundation to final inspection, depending on utility work and City of Houston permitting timelines; a home addition runs 3 to 6 months once permits clear. We give you a written schedule before work starts. Call (254) 272-5240 to talk through your specific site.
We order GAF shingles, underlayment, and TPO per project through our supplier network so the materials arrive fresh and matched to your existing roof. That keeps warranty paperwork clean and means you are not storing pallets of shingles in the driveway. Call (254) 272-5240 for a materials list with your written estimate.
If your addition or ADU roof is failing, or you are planning one and want the GAF spec locked in before framing starts, call (254) 272-5240. Graham Stein and the Elmstead Remodeling Houston team will walk the property, write the price before any work begins, and leave you with a roof assembly that handles Houston storms the same way the rest of your house does. A written price and a covered floor before any work begins, that is where the trust starts.
Written by Graham Stein, Owner, Elmstead Remodeling Houston at Elmstead Remodeling Houston, serving Houston and nearby areas.
