Ply Gem Home Additions & ADU Nationwide | Barrett & Sons Construction

Ply Gem Home Additions & ADU: The Los Angeles Owner’s Guide

Ply Gem home additions and ADU projects in Los Angeles typically run $53,100 to $153,400 installed, depending on square footage, foundation work, and whether we’re tying into the existing roofline or building a detached unit. We stock the Ply Gem trim, siding, and accessory parts most often needed for these builds, and we can have most components on site within a few days. The way most Los Angeles homeowners discover a problem is subtle at first: a cracked piece of Ply Gem vinyl siding near the new addition’s corner, a window that suddenly sticks in its frame, or a gap that opens where the new roof meets the old one.

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Which Ply Gem Models This Applies To

We work with Ply Gem’s full residential exterior line: Mastic vinyl siding (including the Structure Elite and Ovation series), Variform, Napco, and the Ply Gem Premium Collections. For home additions and ADUs in Los Angeles, the most common components we match are Mastic Double 4″ and Double 5″ Dutch lap profiles, which have been installed across Southern California for decades and are still widely available. The compatibility gotcha most owners run into: Ply Gem has changed lock profiles and color lots several times over the years, so a piece of siding bought in 2005 won’t always snap into the same profile sold today, even under the same name. We measure the butt height, the nail hem, and the locking geometry before ordering anything, because “close enough” siding leaks at the laps when the Santa Anas push rain sideways. For OEM versus aftermarket: on structural components like corner posts and J-channel, we use genuine Ply Gem. On trim accessories where Ply Gem doesn’t offer an exact match anymore, we’ll use a quality equivalent that profiles correctly, and we’ll tell you the brand before we install it.

Signs Your Ply Gem Home Additions & ADU Is Failing

• Cracked or buckling siding panels near the roofline. Los Angeles sun and the swing between hot days and cool nights makes vinyl expand and contract. If a panel was nailed too tight during the original build, it’ll buckle and eventually crack at the nail slots.
• Gaps opening at the addition’s corners or where it ties into the house. This usually means the original installer didn’t leave proper expansion clearance, or the foundation has settled. Water finds those gaps fast during winter rains.
• Soft spots or bubbling paint on the interior drywall of the addition. That’s water getting past the exterior. By the time you see it inside, the sheathing behind the siding is already compromised.
• Windows in the addition that stick, fog, or won’t lock cleanly. Ply Gem windows carry a strong warranty, but improper flashing at install is a common failure point. A sticking window often means the rough opening has shifted or moisture has swollen the frame.
• ADU exterior accessories fading unevenly or pulling away. Mounting blocks, light fixtures, and dryer vents that were sealed with leftover contractor caulk instead of proper flashing will pull loose within a few Los Angeles summers.

Replacement Cost & What’s Included

For full Ply Gem home additions or ADU builds in Los Angeles, installed prices run $53,100 to $153,400. That range reflects square footage, foundation type (post-tension slab versus raised perimeter), whether the unit is attached or detached, and how much of the existing exterior we have to tie into. Smaller repair scopes, like re-siding one wall or replacing damaged Ply Gem windows in an existing addition, fall lower, but if you’re here because the addition itself failed structurally, the honest number is closer to a rebuild than a patch. Every quote from Barrett & Sons includes the Ply Gem materials with model numbers, the labor line by line, and the permit fee listed separately. Nothing is lumped under “miscellaneous.” Our workmanship carries the 90-Day Done Right Promise in writing: if it’s not done right, one call brings Tom Barrett back. Ply Gem’s own material warranties apply separately, and we’ll register them for you.

DIY or Call Us?

You can safely check a few things before calling: look at the nail heads on your Ply Gem siding and see if they’re driven tight to the face (they shouldn’t be), check for missing or cracked J-channel around windows, and run a hose along the roofline while someone watches the interior for drips. What you shouldn’t do is pull siding panels off an exterior wall without knowing how the housewrap was origined, what the flashing detail looks like, or whether an electrical run is behind the sheathing. Opening a wall on an addition or ADU and closing it wrong creates a water path that rots the framing inside two winters. That’s the kind of thing we see after a “handyman weekend” goes wrong. If you’d rather talk it through first, call (877) 610-1318 and ask for Tom. We’ll tell you over the phone whether it sounds like a real problem or something that can wait until spring.

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