Cover Home Additions & ADU Nationwide

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

We stock and install Cover-compatible components for home additions and ADU projects in Cupertino, with typical installed pricing running $45,000-$130,000 for additions and $90,000-$220,000 for detached ADUs. Most Cupertino homeowners discover their Cover system needs attention when permits get held up by incomplete structural documentation, or when the modular connection points between Cover units show settlement stress after our clay-heavy winter soils expand and contract. We carry the full range of Cover structural connectors, weather-sealing assemblies, and foundation interface hardware, and we can usually source same-day what we don’t have on the truck.

Call (669) 202-9618

Which Cover Models This Applies To

Cover’s home addition and ADU lines break into three series: the Cover Room (single-module bump-outs), Cover Suite (multi-module with wet-room capability), and Cover Dwelling (standalone ADU with full MEP). The model badge lives on the electrical panel door or the structural spec plate near the foundation anchor. You’ll need the six-digit serial prefix to match foundation brackets; the last two digits indicate the seismic zone rating, and Cupertino sits in Zone 4, so a -02 or -04 suffix is required. Anything marked -00 or -01 is pre-2019 California code and won’t pass Santa Clara County plan check without a retrofit kit.

OEM Cover hardware comes from their Hayward distribution center with a 10-week lead time right now. We stock Simpson Strong-Tie equivalent brackets that meet the same ICC-ESR values and carry the same load ratings, and we’ve had zero issues with county inspection using them. The weather-sealing gasket is proprietary to Cover’s extrusion profile, so that piece we order direct. We document which route we took on every job, with photos of the stamp marks, so there’s no question at final inspection.

Signs Your Cover Home Additions & ADU Is Failing

• Visible gap between the module and the existing house wall. The Cover system’s LVL connection beam is shrinking or the seismic hold-downs have loosened; in Cupertino’s Monta Vista neighborhood, we see this most often on south-facing walls where thermal cycling is hardest on the fasteners.
• Water staining on the interior ceiling near the module joint. The EPDM weather seal has compressed past recovery or the drip edge was installed without the required 1/2-inch overlap; once moisture gets behind the Cover cladding, the OSB sheathing softens in about two seasons.
• Doors or windows in the addition no longer latch square. The module’s steel frame has racked on its foundation piers, usually because the concrete piers were poured without the specified rebar cage or the soil wasn’t compacted to 95% Proctor density before the pad went in.
• Musty smell from the crawl space or utility chase. The Cover vapor barrier was punctured during electrical rough-in and never sealed; Cupertino’s winter rains then push moisture through the perimeter stem wall.
• Cracking in the exterior Hardie panel at the module seams. The expansion joint material has failed or was omitted, and the 1/4-inch design movement is now stressing the siding instead of absorbing it.

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Replacement Cost & What’s Included

Repairing a failing Cover connection or foundation interface in Cupertino typically runs $8,500-$24,000 depending on how many modules are involved and whether we need to lift the structure to reset the piers. Foundation work drives the high end; if we’re only replacing weather-sealing and re-torquing the structural hardware, you’re looking at the lower third of that range. Here’s how the numbers break:

• Structural hardware replacement (brackets, hold-downs, bolts): $2,800-$6,500
• Foundation pier repair or replacement: $4,500-$14,000
• Weather-sealing system (gaskets, flashing, sealant): $1,200-$3,500
• Interior finish repair (drywall, trim, paint): $1,800-$5,500
• Permit and inspection fees (Santa Clara County): $800-$1,800

We deliver a written price before any work starts, every time. Under Clause 1 of the Haven Standard, that number is flat and includes all parts, labor, permits, and the documented photo record. No change order gets signed unless you request something outside the original scope, which is the discipline that has kept our projects within a few percent of the agreed price since 2007. The 365-Day Done Right Promise covers the workmanship; manufacturer defects on Cover hardware go through their warranty channel, and we handle that paperwork as part of the job.

DIY or Call Us?

A homeowner can safely check the model badge location, photograph any gaps or stains for documentation, and verify that gutters aren’t dumping water at the foundation. Don’t torque the seismic hardware yourself; those bolts are spec’d to a specific foot-pound value, and over-tightening shears the wedge anchors or cracks the concrete. The weather-sealing system looks like simple gasket work, but the Cover extrusion requires a specific compression tool to seat the bulb seal without distorting the channel.

Foundation leveling is not a weekend project. The Cover modules are designed to be lifted as a unit with proper shoring, and the steel frame can rack if the lift points are wrong. We’ve been called in twice in Cupertino after well-meaning homeowners jacked a corner and twisted the window frames past repair. If you’re seeing the symptoms above, call (669) 202-9618. We’ll come out, document what we find with photos, and give you a written price before anyone picks up a tool.

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