CertainTeed Home Additions & ADU Nationwide

CertainTeed Home Additions & ADU: The Sherman Oaks Owner’s Guide

We stock and install CertainTeed-compatible building systems for home additions and ADUs in Sherman Oaks, with typical installed project costs running $45,000-$130,000 for additions and $90,000-$220,000 for detached ADUs. Most CertainTeed material orders arrive within 3-5 business days, and we coordinate delivery to avoid holding up your framing schedule. Sherman Oaks homeowners usually discover a problem when their architect’s spec calls for CertainTeed WeatherBoards fiber cement siding or CertainTeed vinyl window systems and the contractor can’t source the exact profile, or when an existing CertainTeed roof-to-wall transition on an older addition starts leaking after the Valley’s Santa Ana wind cycles loosen the flashing.

Call (213) 221-0788

Which CertainTeed Models This Applies To

CertainTeed’s building envelope products for additions and ADUs break into three families that we regularly match in Sherman Oaks. The WeatherBoards fiber cement line comes in 5/16″ and 7/16″ thicknesses, with the 12-foot plank lengths most common for second-story additions where fewer seams mean less caulking maintenance. Vinyl siding spans the MainStreet, Monogram, and Cedar Impressions collections, each with a different exposure width and locking tab geometry that must match existing courses if you’re tying into a current wall plane. For roofing transitions on additions, we see the Landmark architectural shingle most often, though Grand Manor and Belmont turn up on higher-end builds in the hills south of Ventura Boulevard.

To identify your exact product, check the nail hem or backside of a loose plank for the stamped date code and product run. The color name alone isn’t enough; CertainTeed reformulated several vinyl colorants after 2019, and a “Colonial White” from 2016 won’t match a 2022 run exactly. We carry a color-matching spectrophotometer on our truck for this reason. OEM CertainTeed parts guarantee warranty continuity, but we also source compatible aftermarket profiles from Royal Building Products and Ply Gem when the original line has been discontinued. For fiber cement, we won’t substitute; the warranty and fire rating are too specific to risk a lookalike.

Signs Your CertainTeed Home Additions & ADU Is Failing

• Buckled or warped siding planks. This usually traces to inadequate nailing schedule or fasteners driven flush instead of leaving the 1/32″ gap CertainTeed specifies. In Sherman Oaks, the thermal swing between 110°F August afternoons and 45°F January mornings exaggerates the movement, and locked-in planks eventually oil-can.
• Water staining at ceiling joints where addition meets original roof. The step flashing beneath CertainTeed shingles may have been counterflashed with caulk instead of metal. Caulk dies in UV; metal doesn’t. We find this most often on 1990s additions in the flatlands near the Galleria, where the original builder cheated the detail.
• Cracked fiber cement at corners or window openings. CertainTeed WeatherBoards requires 1/4″ gap at all trim edges with backer rod and sealant. When installers butt it tight, the plank fractures as it expands. The crack looks like a hairline at first, then admits water.
• Vinyl siding panels that have come unzipped below the bottom lock. The locking tab fatigues after 15-20 years of heat cycling, especially on south and west walls in Sherman Oaks. Once the wind gets under a loose panel, it tears the nailing hem and the course below it.
• Drafty rooms or elevated HVAC bills after an addition. CertainTeed’s CertaWrap house wrap or CedarBreather ventilation mat may have been omitted or improperly lapped at the sill plate. Air infiltration at the foundation junction is the culprit we find most often on ADU conversions.

Before

After

Replacement Cost & What’s Included

What drives the range: foundation type (slab-on-grade vs. raised perimeter), whether we’re tying into existing structural systems or building freestanding, and the CertainTeed product tier selected. WeatherBoards runs roughly 40% more than vinyl for material but carries a Class A fire rating that satisfies Los Angeles County requirements in high-fire-severity zones near the Santa Monica Mountains. Every quote we write itemizes labor, material, permit fees, and a line for contingency. Under Clause 1 of The Haven Standard, that written price is fixed; no change order moves forward without your signature, which is how we’ve kept 4,000-plus projects within a few percent of the original number since 2007. Our 365-Day Done Right Promise covers the workmanship; CertainTeed’s own product warranty runs 50 years on vinyl siding and 25 years on fiber cement.

DIY or Call Us?

There’s a safe middle ground here. A homeowner can walk the perimeter with a camera, note the product stamps on loose planks, and check the CertainTeed website for current availability of that color and profile. That’s useful reconnaissance, and we welcome it. What we don’t recommend is removing fiber cement planks yourself; the silica dust requires OSHA-compliant respirators and containment, and a 12-foot plank of 7/16″ WeatherBoards weighs enough to damage what’s below it if dropped. Roof-to-wall flashing work involves ladder work at height and often requires a permit in Los Angeles; the Building & Safety office on Erwin Street will flag unpermitted structural work on resale. For vinyl panel replacement, the locking tab geometry varies by series, and forcing the wrong profile cracks the course above. Measure twice, write it down, then build it. If you’ve got the measurements and photos, call us at (213) 221-0788 and we’ll confirm compatibility before we quote.

FAQs