CGI Home Additions & ADU Nationwide

CGI Home Additions & ADU: The Mountain View Owner’s Guide

CGI-compatible home additions and ADU construction in Mountain View typically runs $45,000-$130,000 for additions and $90,000-$220,000 for detached ADUs, with most projects quoted within 48 hours and permits pulled before ground breaks. We stock and install framing hardware, structural connectors, and weather-resistant flashing systems that match CGI specifications across their residential product lines. Most Mountain View owners first realize something’s off when their addition’s drywall cracks along the seam where old meets new, or when the ADU’s roofline doesn’t shed water the way the main house does - both signs the structural integration or moisture barrier failed at the connection point.

Call (669) 215-4852

Which CGI Models This Applies To

CGI doesn’t sell complete additions or ADUs as packaged units - they manufacture the structural components, connectors, and engineered lumber that contractors use to tie new construction to existing framing. The critical match points are the post base brackets, hold-down anchors, and lateral-load connectors specified in CGI’s catalog for seismic zones like Mountain View’s Zone 4 classification. You’ll find the part number stamped on the steel bracket itself, usually starting with “CGI-” followed by a load rating in pounds - a CGI-HD8, for instance, is an 8,000-pound hold-down, not interchangeable with a generic HD7 from the hardware store.

We source OEM CGI hardware direct from their West Coast distributor in San Jose, which keeps lead times under three days for standard brackets and under a week for custom-length LVL beams. For structural screws and powder-actuated fasteners, we often substitute Simpson Strong-Tie equivalents that carry the same ICC-ES report and cost 15-20% less - we note the substitution on the quote, and no substitution proceeds without the homeowner’s initials next to the line item. That’s Clause 1 of the Haven Standard: the written price shows exactly what you’re getting.

Signs Your CGI Home Addition or ADU Is Failing

• Cracking drywall at the old-to-new junction. The differential settlement between original foundation and new footing - common in Mountain View’s clay-heavy soil near Permanente Creek - overstressing the CGI connector bolts. We see this most in additions built during the 2015-2019 rush before updated geotech requirements.
• Water staining on ceiling drywall below the addition roofline. The step flashing where the new roof meets existing wall was either omitted or installed without the required 4-inch vertical leg that CGI’s detail drawings specify. Mountain View’s winter wind-driven rain finds that gap fast.
• Doors or windows in the ADU that won’t latch properly. Lateral movement in the hold-down system, often from a CGI post base that wasn’t bolted to the foundation with the required epoxy adhesive in addition to mechanical anchors. The frame racks; the door goes out of square.
• Squeaking or bouncy floors in the addition. The I-joist or LVL beam span exceeds CGI’s published load table for the depth used, or the rim board wasn’t glued and screwed per spec. We find this in owner-permitted ADUs where the framer sized the beam by eye.
• Exterior siding pulling away from the corner boards. Missing or improperly lapped housewrap at the addition’s sheathing transition, letting moisture swell the OSB and push the siding outward. CGI’s details call for a minimum 6-inch overlap onto existing weather barrier.

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Replacement Cost & What’s Included

Repairing a failed CGI structural connection or moisture barrier in Mountain View runs $4,500-$18,000 depending on how much finishes need to come off to access the problem. A localized hold-down replacement with stucco repair and paint match sits at the low end; a full roof-to-foundation reflash with interior drywall replacement hits the high end. Our written quote breaks out labor, materials, and permit costs separately - no lump-sum mystery. The $45,000-$130,000 range for full additions and $90,000-$220,000 for ADUs reflects complete construction, not repair work.

Every repair includes a documented photo record of the concealed condition before we cover it, a signed change order if we find rot or termite damage that wasn’t visible, and our 365-Day Done Right Promise. If the crack returns or the stain reappears, we make it right. No asterisk - the terms are printed on the contract.

DIY or Call Us?

An owner can safely check the visible symptoms: photograph the crack pattern, measure door gaps with a dollar bill, look for missing flashing from a ladder at the roof junction. What you cannot safely do is remove a structural connector to inspect it - these brackets are tensioned to resist seismic loads, and disturbing the bolt pattern without temporary bracing compromises the whole system. We’ve been called to Mountain View jobs where a homeowner’s “quick look” turned a $3,000 flashing repair into a $12,000 structural rebuild.

Call (669) 215-4852 and we’ll schedule a free evaluation. We bring the right temporary bracing, document what we find with photos you keep, and give you a written price before any repair starts. Measure twice, write it down, then build it that way.

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