Metal roofing
Architectural shingles
Tile roofing
GAF
Owens Corning
Flat & low-slopeFree roof inspection with deck photos before we talk money - GAF and Owens Corning certified installation
GAF Roofing in Simi Valley, CA | Mercer Roofing Co Woodland Hills
We provide independent GAF roofing service across Simi Valley, from the 1960s ranch tracts off Erringer Road to the newer hillside builds that bake in summer sun. The one thing that makes our GAF work here different is that we plan every job around what Simi Valley actually does to a roof: intense UV, Santa Ana gusts, and wildfire-zone code. That shapes which GAF products we recommend, how we flash valleys, and what we tell you about sheathing before a single shingle comes off. Call (341) 217-2677 for a free estimate.
Why Simi Valley Residents Choose Us for GAF Service
Grant Whitlock has been putting roofs on homes across the Valley for well over a decade. He learned the trade through the construction technology program at Los Angeles Trade-Technical College, and he still talks like the guy who walked the Warner Center corridor roofs where summer heat tells you everything about whether a flat roof was done right. Around Simi Valley, our crews from our Roofing Company in Simi Valley work on GAF roofs in the older tracts and the hills, so we know how Timberline and 3-tab shingles behave after a decade of Simi Valley sun. We use genuine GAF shingles and accessories when matching an existing roof or protecting a warranty, and we keep common GAF profiles ready for Simi Valley jobs so you are not waiting on a warehouse in another county. Every technician who arrives at your door is background-checked, identity-verified, and wearing a photo ID badge. We send you their name and photo before they show up. A written price comes before any work starts, every time.
Styles & brands we work with






Common GAF Roofing Problems We Solve in Simi Valley
- UV-induced granule loss and brittleness on older GAF 3-tab shingles. South-facing slopes in Simi Valley take relentless sun, and on older Royal Sovereign and 3-tab roofs we see granules washing into gutters and shingles that crack when you lift them. Repair only makes sense if the rest of the roof has years left; otherwise we price out replacement.
- Wind uplift and shingle blow-off during Santa Ana events. GAF Timberline roofs can lose shingles at rakes and eaves when gusts hit 60+ mph through the passes. We check nailing patterns and seal strips, then re-secure or replace with wind-rated GAF products where needed.
- Leaks at valley metal and vent boots. Many original GAF flashing details in Simi Valley were never upgraded to current code, and after years of thermal movement they separate. We pull the old valley metal, inspect the decking, and install new flashing with proper underlayment.
- Premature underlayment deterioration on low-pitch ranch roofs. Low-slope ranch homes trap heat and moisture, and old felt underlayment breaks down faster than anyone expects. When we reroof, we often upgrade to synthetic underlayment better suited to Simi Valley’s heat.
- Spaced sheathing under old wood shake. In Simi Valley’s older tracts, original spaced sheathing sits under wood shake roofs. GAF shingles cannot be installed directly over it. We resheathe with plywood first, which is also a GAF warranty prerequisite.
GAF Service in Simi Valley: What Local Conditions Mean for Your Roof
In the Bird Streets off Erringer Road, the original spaced sheathing under wood shake changes everything about a GAF reroof. Those houses were built with gaps between the boards, because wood shake needed airflow underneath. Modern GAF shingles need a solid, code-compliant deck. We have opened roofs in that neighborhood and found sheathing so dried and cupped that it would flex under foot traffic. Before any GAF Timberline HDZ shingle goes down, we resheathe with plywood, add upgraded valley metal and vent boots, and bring the roof to Class A fire-rating for the wildfire hazard zone. It adds cost and time that many Simi Valley homeowners do not see coming, and it is a GAF warranty prerequisite. A neighbor in Agoura Hills or Woodland Hills might face the same code requirements, but the Bird Streets’ original construction makes this the rule, not the exception. Not knowing it upfront is how people end up with change orders. We put it in the written price before we start.
GAF Models & Products We Service in Simi Valley
Our Simi Valley crews service and install GAF Timberline HDZ, Timberline Ultra HD, Royal Sovereign, and standard 3-tab shingles. We use genuine GAF shingles and accessories when matching existing roofs or keeping warranty coverage intact. For underlayments and flashings, we often recommend quality aftermarket products that hold up better under Simi Valley’s UV and wind. We stock common GAF profiles and accessory colors for fast turnaround on Simi Valley repairs, so your roof does not sit open longer than it has to. Learn more about our GAF sales & service.
See the difference
Before
After
Before
After
Before
AfterGAF Service Pricing in Simi Valley
Shingle replacement on a typical Simi Valley ranch home runs roughly $8,500 to $15,000 for a full reroof, depending on whether resheathing is needed. Repairs like valley flashing or a few wind-blown shingles typically fall between $350 and $1,200. The Bird Streets resheathing scenario adds real cost, because plywood, labor, and disposal are not optional. Every estimate includes a written line-item price before work starts, and every repair carries a written guarantee with a free second visit if it fails. That is the 365-Day Done Right Promise. Call (341) 217-2677 for an exact quote, estimates are free.
Serving Simi Valley, CA - Our Local Coverage Area
We’re based in the Simi Valley area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs – GAF Roofing in Simi Valley
Yes, in wind-exposed areas of Simi Valley we install GAF shingles with a higher nail count, proper seal strip activation, and reinforced rake and eave details to resist uplift. Standard installation from calmer regions will not hold up here. Call (341) 217-2677 to talk through what your roof needs.
No. GAF requires a solid deck, and Simi Valley code does too. We resheathe with plywood before any GAF shingle goes down. Skipping that step voids warranty coverage and creates a roof that flexes and leaks. Call (341) 217-2677 for a resheathing estimate.
Simi Valley’s intense UV exposure accelerates granule loss and can make shingles brittle faster than coastal locations. South-facing slopes are worst. We see Timberline roofs here that look ten years older than their age, and we recommend ventilation and lighter shingle colors on full replacements to slow the damage.
Yes, GAF Timberline HDZ and Ultra HD shingles carry a Class A fire rating when installed with the correct underlayment and decking, which satisfies Simi Valley’s wildfire-zone requirements. We confirm the specific rating for the product and assembly before we quote. Call (341) 217-2677 to check your zone.
Thermal movement from Simi Valley’s hot days and cool nights repeatedly expands and contracts the valley metal, eventually breaking the seal at laps and fasteners. Old valley metal on ranch-style homes is a common leak point. We replace it with wider metal and proper underlayment. Call (341) 217-2677 for a valley inspection.
Service Areas Near Simi Valley
We run GAF service throughout Simi Valley and into the surrounding communities. Our crews cover Woodland Hills, Agoura Hills, Topanga, West Hills, and Winnetka. You can see our full Simi Valley service area, or read about GAF service in Agoura Hills and GAF service in Woodland Hills.
Book Your GAF Service in Simi Valley Today
Whether it is a leak, wind damage from the last Santa Ana, or a full reroof on a Bird Streets home, our Roof Repair in Simi Valley will put the price in writing before we start. A roof should be the last thing you worry about. Let’s make sure it is. Call (341) 217-2677 to schedule your free estimate.
Written by Grant Whitlock, Owner at Mercer Roofing Co Woodland Hills, serving Simi Valley and the surrounding Valley communities.