CGI Home Additions & ADU Nationwide

CGI Home Additions & ADU: The Cupertino Owner’s Guide

We stock and install CGI-compatible windows and doors for home additions and ADU projects in Cupertino, with installed pricing typically running $45,000-$130,000 for full additions and $90,000-$220,000 for detached ADUs depending on foundation, utility tie-ins, and CGI unit count. Most Cupertino homeowners discover their CGI windows or doors are failing when they feel drafts around the sash, see condensation between glass lites, or notice the locking hardware no longer seats flush - symptoms that worsen during Santa Clara Valley’s wet winters and dry, expansion-prone summers. In Monta Vista and the older Ranchos neighborhoods, we regularly see CGI units installed during the 2005-2015 building boom reaching the end of their weep screed and sealant life cycle.

Call (669) 202-9618

Which CGI Models This Applies To

CGI’s product lines for residential additions and ADUs fall into three main series: Estate Collection (aluminum impact), Sentinel by CGI (vinyl impact), and Targa by CGI (hybrid aluminum-vinyl). The Estate line uses a 2-5/8″ frame depth with integrated fin installation, while Sentinel units measure 2-3/4″ and rely on a nail-fin or block-frame application depending on the substrate. To identify your exact unit, check the etched mark in the glass corner - it’ll read “CGI” plus a four-digit code that maps to the series and glazing specification. The hardware stamp on the lock mechanism (usually Hoppe or Truth brand for CGI) confirms the vintage.

We are an independent service provider, not affiliated with CGI. For OEM replacement sashes, we source through CGI’s distribution network; for frame and hardware repairs, we often specify truth-equivalent aftermarket components that carry the same DP-50 pressure rating at lower lead time. The compatibility gotcha in Cupertino: Estate Collection units from 2008-2012 used a proprietary interlock geometry that aftermarket sashes won’t match without adapter trim. We verify this with a field measurement before ordering.

Signs Your CGI Home Additions & ADU Is Failing

• Draft at the sash meeting rail. The wool pile weatherstrip compresses permanently after 10-15 years of Santa Clara Valley’s UV exposure and thermal cycling, breaking the pressure seal. We find this first on south- and west-facing walls in Cupertino’s Monta Vista area, where afternoon sun loads are highest.
• Fog or moisture between glass panes. The insulating glass unit’s edge seal has failed, allowing humid air to enter the airspace. In Cupertino’s climate, this typically appears after 12-18 years - sooner if the unit was installed without proper shimming, which stresses the seal.
• Locking hardware binds or won’t fully engage. The multipoint lock mechanism accumulates aluminum oxide, or the keeper plate shifts as the frame expands and contracts. Left unaddressed, the misalignment transfers load to the hinge side and distorts the sash.
• Visible corrosion at the weep screed or sill nose. Coastal moisture from the Bay, carried on prevailing westerlies, attacks exposed aluminum where the anodized coating has worn. We see this most on first-floor units without adequate overhang protection.
• Operation feels heavy or the sash drops when opened. The balance system - either a constant-force coil or block-and-tackle type depending on CGI vintage - has lost tension. A dropping sash is a pinching hazard and accelerates frame wear.

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Replacement Cost & What’s Included

For Cupertino homeowners, CGI window and door replacement within a home addition or ADU project runs $800-$2,400 per opening for like-for-like sash replacement, and $1,800-$4,500 per opening for full frame-and-sash replacement with new trim and sealant. The range depends on unit size, floor level (second-story requires scaffolding or ladder work), and whether the original installation used CGI’s integrated fin or a retrofit block frame.

Our written quote itemizes: the CGI or equivalent unit cost, labor by opening, disposal of the old unit, new sealant and backer rod, and a finish touch-up to the interior trim. Under Clause 1 of The Haven Standard, that price is fixed before work starts; no change proceeds without a signed change order. The 365-Day Done Right Promise covers installation workmanship, and the glazing unit carries the manufacturer’s 20-year seal-failure warranty.

DIY or Call Us?

An owner can safely check the etched glass code, photograph the lock hardware stamp, and confirm the rough opening dimensions with a tape measure. What goes wrong in DIY: ordering a sash without verifying the interlock geometry, which leaves a 1/4″ gap at the meeting rail; or removing a fixed sash without supporting the frame, which racks the opening and cracks the adjacent drywall. The balance system on CGI’s larger units stores significant spring tension - release without proper tools can damage the mechanism and the frame.

We carry common CGI hardware, weatherstrip profiles, and balance assemblies on our Cupertino service vehicles. For full sash or frame replacement, we measure in person and order to spec. Call (669) 202-9618 to schedule your free estimate.

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