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CertainTeed Home Additions & ADU: The West Covina Owner’s Guide
A full home addition or ADU built with CertainTeed exterior products in West Covina typically runs $45,000 – $130,000 installed, depending on square footage, foundation work, and how much of the existing structure ties into the new one. We stock the CertainTeed siding, trim, and roofing lines most West Covina additions use, and we can usually start your project within two to three weeks of the signed written price. Most homeowners call us because they see gaps opening where the addition meets the original house, water staining on CertainTeed siding, or failing flashing around windows and roof transitions.
The frustrating part is that the failure often isn’t the CertainTeed product itself. It’s how the original contractor tied the new structure into the old one. West Covina’s hot, dry summers and occasional heavy winter rain make expansion and contraction a constant issue, especially on south-facing walls off Merced Avenue or up in the hills above Cameron Park. When we open up a failing addition, we usually find the same three things: missing kickout flashing where roof meets wall, siding installed without the proper clearance gap at seams, or stucco that was patched over a gap instead of properly joined.
Which CertainTeed Models This Applies To
CertainTeed home additions and ADUs in West Covina almost always involve one of three product families: Cedar Impressions or Monogram vinyl siding, WeatherBoards fiber cement, or the Landmark roofing line. The siding is where compatibility matters most. Cedar Impressions runs thicker than standard vinyl, which means the J-channel and trim accessories need to match that product line specifically, not whatever was cheapest at the supply house. WeatherBoards is a different animal entirely because it’s fiber cement, and it needs the CertainTeed-rated fasteners and proper gap spacing or the boards will swell at the butt joints after the first winter rain.
If you’re trying to match existing siding, look for the CertainTeed label printed on the back of a removed panel, or measure the exposure. Cedar Impressions has a distinct double-7-inch staggered look that’s deeper than economy vinyl, and the color codes are stamped on the carton, not the panel. We’re an independent provider, not affiliated with CertainTeed, but we’ve installed enough of it across West Covina to know which aftermarket trim works and which fails. For most additions, we recommend OEM CertainTeed for the face panels and allow quality aftermarket for the hidden accessories where it doesn’t affect the warranty or the look. The one thing we won’t substitute is the flashing, because that’s where West Covina additions fail first.
Styles & brands we work with
Signs Your CertainTeed Home Additions & ADU Is Failing
- Gap opening at the addition’s roofline where it meets the original house. This is usually the result of the new foundation settling at a different rate than the old one, which is common in West Covina neighborhoods like Woodside and South Hills where the soil shifts seasonally.
- Water staining or soft spots on CertainTeed siding near windows and corners. The siding itself rarely fails. What fails is the flashing behind it, and by the time you see the stain, the sheathing underneath has been wet for months.
- Caulk pulling away from window and door trim on the addition. CertainTeed’s exterior products expand and contract with temperature swings, and West Covina’s 80-plus degree summer days followed by cool nights will work that caulk out within a few years if it was applied wrong.
- A musty smell in the room closest to the addition. That odor means moisture is finding its way in somewhere, and in additions built over crawl spaces, it’s often the skirting or foundation vents that were never flashed properly.
- Doors inside the addition that stick in summer but close fine in winter. That’s the frame moving, which tells us the addition wasn’t tied into the existing structure with the right hardware or wasn’t given proper expansion allowances at the connection points.
See the difference
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AfterReplacement Cost & What’s Included
For a full CertainTeed home addition or ADU in West Covina, plan on $45,000 – $130,000. A straight garage conversion with CertainTeed siding runs $30,000 – $80,000, which is the lower end because the foundation and roof structure already exist. The price climbs when we’re cutting into the original roofline, pouring new foundation, or running new electrical service from the street.
Every price we give is written before work starts. That’s not a promotion, it’s how we operate. The number includes materials, labor, permits, and the connection points between old and new construction. What it doesn’t include are surprise change orders, because we don’t do those. If we find a problem behind the existing wall when we open it up, we stop, show you what we found, and put the revised number in writing before we go further. Isaac Pruett has said it on jobsites across the San Gabriel Valley for years: you should know what you’re getting before we ever pick up a tool. Our workmanship on additions and ADUs is covered for 365 days from the completion date, and if something we built fails in that window, we come back and make it right at no charge.
DIY or Call Us?
You can absolutely inspect the exterior of your addition yourself. Walk the perimeter, look for gaps, check that caulk lines are intact, and make sure the siding’s weep holes aren’t painted over. Those are the things that tell you early whether you have a problem brewing. What you shouldn’t do is cut into the wall or pull siding panels to investigate. By the time you’ve exposed the framing, you’re into structural and weatherproofing territory, and a bad flash job on a West Covina home means water in the wall cavity with no exit.
The bigger issue is that a home addition ties into the roof, the foundation, and the weather envelope of your existing house. Get any one of those connections wrong and you’re not fixing a part, you’re redoing a whole corner of your home. If you see water stains, door alignment problems, or gaps opening at the roofline, call (707) 760-7579 and we’ll come look at it. A second set of experienced eyes costs you nothing, and the inspection comes with a straight answer about whether it needs work now or can wait.
FAQs
With proper flashing and correct installation, a CertainTeed addition should last 30 to 50 years before the exterior needs major attention. The weak link isn’t the siding or roofing, it’s the connection points, and in West Covina’s climate those need checking every two to three years. Call (707) 760-7579 if you want us to inspect yours; there’s no charge for the visit.
Most of the time, yes. If the framing is dry and sound, we can remove the siding in the affected area, correct the flashing, replace any damaged sheathing, and reinstall the CertainTeed product so it matches. The exception is when water has been getting in for years and the framing itself is compromised, which is when costs go up fast. We’ll show you what we find before we quote anything.
A detached ADU in West Covina typically takes four to seven months from first dig to final inspection. A garage conversion runs eight to fourteen weeks, and a room addition attached to the existing house usually lands somewhere between. The permitting process with the city is often the longest single piece, and we handle all of it.
We keep common CertainTeed lines stocked at our West Covina yard, and we also work with KraftMaid, Cambria, and Silestone for the interior finish work on additions and ADUs. If your project needs a specific CertainTeed color or profile we don’t have on hand, we can usually have it within a week through our supplier network. Call (707) 760-7579 and tell us what you’re matching; we’ll check stock while you’re on the phone.
If your CertainTeed addition or ADU is showing signs of trouble, or you’re planning one and want a straight price before you commit, call (707) 760-7579. We’ll walk the project with you, put the number in writing, and tell you exactly who’s coming to your door, by name and photo, before they arrive.
Written by Isaac Pruett, Owner, Mason Remodeling Co West Covina at Mason Remodeling Co West Covina, serving West Covina and nearby areas.
