CGI Home Additions & ADU Nationwide

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

CGI home additions and ADU construction in Sunnyvale typically runs $45,000-$130,000 for a standard addition and $90,000-$220,000 for a detached ADU, with most Rowan projects priced within 3% of the written quote once complete. We stock and install CGI-compatible framing hardware, structural connectors, and finishing systems across the full product line, and we carry the most common failure items on our trucks. Most Sunnyvale homeowners discover an issue when a permit inspection flags a structural connector mismatch, or when settling in the Lakewood Village clay soils causes a beam pocket to shift and crack the drywall at the addition joint.

Call (650) 405-3637

Which CGI Models This Applies To

CGI, or California General Industries, manufactures structural hardware for residential additions and ADUs in three main series: the HD (Heavy Duty) line for single-story stick-frame additions, the UHD (Ultra Heavy Duty) line for two-story or engineered-lumber applications, and the ADU-Slim line designed for the tighter clearances common to garage conversions and backyard cottage builds. The part number is stamped on the connector face, usually beginning with HD-, UHD-, or AS- followed by the gauge and load rating. For example, an HD-44-2.5 is a 14-gauge, 2.5-inch strap tie rated for 1,055 pounds of tension in Douglas fir.

The critical compatibility gotcha in Sunnyvale’s 94086 and 94087 zones: older HD-series connectors installed before 2019 may not meet the current Santa Clara County wind-load requirements for exposed ADU structures, even if the metal looks sound. We verify the stamp date against the county amendment cycle before quoting. For OEM-versus-aftermarket, Simpson Strong-Tie produces cross-compatible equivalents with identical gauge and nail schedules, and we stock both. The Simpson version often ships faster, but for ADU-Slim brackets with the recessed bolt pattern, only the CGI original fits without field modification.

Signs Your CGI Home Additions & ADU Is Failing

• Cracked drywall at the addition joint. The beam pocket or ledger connector has shifted, often from seasonal clay expansion in Sunnyvale’s Lakewood Village area, and the CGI strap tie has elongated or pulled a nail. The crack returns after patching because the structure is still moving.
• Sagging header above a new opening. The UHD hanger specified for the engineered lumber was swapped for a lighter HD unit during construction, or the wrong nail schedule was used - 10d common where 16d was spec’d. The hanger deforms gradually until the trim reveals it.
• Corrosion blooming on exposed ADU hardware. Sunnyvale’s marine air layer from the Bay accelerates galvanic corrosion on zinc-coated connectors, especially within a mile of the Caltrain corridor. The white rust reduces the connector’s rated capacity before visible pitting appears.
• Nails backing out of joist hangers. This is usually a sign of overdriven fasteners or the wrong angle - face nails where skewed nails were required. The hanger loosens, the joist drops, and the floor above goes soft.
• Permit red-tag at rough inspection. The inspector finds a CGI AS-series bracket on a load-bearing shear wall where an A35 or LTP4 was specified in the plans. The part looks similar but the nailing pattern and load path differ by 40%.

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After

Replacement Cost & What’s Included

The range depends on access - attic crawl versus open framing - and whether the county requires a structural observation, which adds $450-$800 for the engineer’s site visit. Our quote lists CGI parts, Simpson equivalents if applicable, labor hours, and permit fees separately. Under Clause 1 of the Haven Standard, that written price is fixed; no change proceeds without a signed change order. The 365-Day Done Right Promise covers the installation and the hardware.

DIY or Call Us?

A homeowner can safely check the part stamp and compare it to the approved plans - that’s documentation, not structural work. But removing and replacing a load-bearing connector is not a DIY project. The connector is part of a calculated load path; swap a 16-gauge for a 14-gauge, or use the wrong nail angle, and you’ve changed the shear capacity without knowing it. In Sunnyvale, the county inspector will catch it, but only after the drywall is up and the permit is red-tagged.

We carry HD-44, UHD-46, and AS-36 brackets on the truck, plus the full Simpson cross-reference. If you’re staring at a cracked addition joint or a red tag, call (650) 405-3637. We’ll scope it, photograph it, and deliver a written line-item estimate before any work starts. Measure it twice, write it down, then build it.

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