Cover Home Additions & ADU Nationwide

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

Cover home additions and ADU systems in Mountain View typically run $45,000-$130,000 installed, depending on whether you’re extending an existing structure or building a detached unit from the foundation up. We stock Cover-compatible framing hardware, structural connectors, and weather-sealing systems on our Mountain View trucks, and most replacement or repair work can be scheduled within a few business days. Most owners first realize something’s wrong when they spot water intrusion at the addition joint, feel a temperature swing they can’t explain, or notice the floor has settled enough to crack tile near the seam.

Call (669) 215-4852

Which Cover Models This Applies To

Cover’s home addition and ADU product lines span three generations of hardware, and the mounting brackets, header beams, and thermal break gaskets are not interchangeable across them. The first-generation Cover Series 100, common in Mountain View builds from 2012-2018, uses a 4-inch galvanized post base with a single shear plate; the Series 200 and 300 shifted to a 6-inch base with dual shear plates and a composite thermal break. You’ll find the series number stamped on the interior face of the post base, usually visible in the crawl space or basement. If that tag is corroded, measure the post width: 4-inch means Series 100, 6-inch means 200/300. The 200 and 300 share the same footprint but use different gasket profiles, so bring the old gasket or a photo if you’re matching it yourself. We carry OEM Cover hardware and structural equivalents from Simpson Strong-Tie that meet or exceed the same load ratings, and we’ll note which we’re quoting in writing before work starts.

Signs Your Cover Home Additions & ADU Is Failing

• Water staining at the ceiling or wall joint where the addition meets the original structure. This usually means the flashing between the existing roofline and the new roof has lifted or the step flashing was never integrated properly with the Cover header system. In Mountain View, the dry summers bake the sealant brittle, then winter rains find the gap.
• Floors that feel soft, slope, or have cracked tile near the addition seam. The post base may have settled due to inadequate compaction during original construction, or the galvanized base itself has corroded where groundwater collects. We’ve seen this more often in the older Castro Street area homes with clay-heavy soil.
• Temperature differences of 8-15 degrees between the addition and the main house. The thermal break gasket in the Cover header beam has compressed or shifted, breaking the thermal bridge. This shows up on PG&E bills before it shows up on a thermostat.
• Doors or windows in the addition that stick, rub, or won’t latch. Differential settlement between the original foundation and the addition’s pier or slab has racked the frame. The Cover system is designed to accommodate minor movement, but beyond 1/4 inch over 8 feet, the hardware binds.
• Visible rust weeping from post bases or connector plates. Mountain View’s occasional high water table and the salt air that pushes inland on certain wind patterns accelerate galvanic corrosion. Once the zinc layer is compromised, the steel underneath goes fast.

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Replacement Cost & What’s Included

Here’s how Cover home addition and ADU work breaks down in Mountain View:

The wide range reflects foundation type, soil conditions, and whether we’re matching existing finishes or starting fresh. Every quote we write in Mountain View includes the parts list, labor hours, permit fees, and a line for contingencies that requires your signature before we spend it. Under Clause 1 of the Haven Standard, that written price is fixed before anyone picks up a tool. Our 365-Day Done Right Promise covers the workmanship, and the documented photo record we deliver at completion shows every post base, every connector, and every sealed joint.

DIY or Call Us?

There’s a short list of checks a Mountain View homeowner can safely make: confirm the series number on the post base, look for rust or water stains with a flashlight, and photograph any gaps between the addition and main structure for documentation. What you should not attempt is jacking or shimming a settled post, cutting into a load-bearing header to inspect it, or removing flashing to “see what’s underneath.” The Cover system is engineered to transfer roof and floor loads through specific paths; disturb one connector without temporary support and you’ve changed the load path for the whole assembly. We carry the temporary shoring equipment, the torque-rated fasteners, and the structural epoxy on our Mountain View trucks. Call (669) 215-4852 and we’ll schedule a free estimate with a written scope before any work starts.

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