Tamko Home Additions & ADU Nationwide

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

We stock and install Tamko-compatible roofing, flashing, and waterproofing components for home additions and ADU projects in Mountain View, with typical installed pricing for addition work running $45,000-$130,000 and ADU construction at $90,000-$220,000 depending on foundation type and tie-in complexity. Most Mountain View homeowners discover their Tamko system needs attention when an inspector flags membrane separation at the addition tie-in during a sale or refinance, or when water stains appear on the ceiling below a new dormer after the first heavy winter rains. In the older neighborhoods near Castro Street, we regularly see original Tamko Heritage shingles on 1960s ranch additions that have reached the end of their service life but were never integrated properly with the primary roof drainage plane.

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Which Tamko Models This Applies To

Tamko’s residential product line that intersects with addition and ADU work includes the Heritage series architectural shingles (Heritage, Heritage Vintage, Heritage IR), the Titan XT impact-resistant line, and the MetalWorks steel shingle system. For waterproofing at addition tie-ins and ADU roof-to-wall junctions, the critical components are Tamko’s TW Metal Edge flashing, TW-Underlayment synthetic underlayment, and the TW-Drain EPDM membrane system used at valleys and dead-level crickets behind parapets on flat-roofed ADUs.

To identify what you have, check the shingle back for a printed date code and series name, or look for a Tamko specification sheet in your permit folder if the addition was permitted after 2010. The OEM-versus-aftermarket decision matters most on the membrane side: Tamko’s TW-Drain is a 60-mil EPDM with a specific fleece backing that bonds to their TW-Underlayment, and substituting a generic 45-mil EPDM without that interface layer is the compatibility gotcha we see most often in Mountain View. It’ll hold for two seasons, then delaminate at the seam. We stock both genuine Tamko membrane and a vetted aftermarket equivalent that matches the 60-mil spec and fleece interface, and we quote both with the part number written on the line item so you know what you’re getting.

Signs Your Tamko Home Additions & ADU Is Failing

• Water staining on the ceiling directly below the addition ridge or valley. This usually indicates the Tamko underlayment has degraded at a penetration or the step flashing was omitted where the addition roof meets the existing wall. The Heritage shingle itself may look fine from the ground; the failure is underneath it.
• Granule accumulation in gutters below the addition slope. Tamko Heritage shingles lose granules as they age, but accelerated loss on an addition often means the slope was built below the 4:12 minimum for that shingle series, or ventilation was inadequate and the shingles cooked. We see this on south-facing ADU roofs in Mountain View’s warmer microclimates near the foothills.
• Lifted or cupped shingle tabs at the addition perimeter. This is typically wind damage, but on additions it often traces to improper starter strip installation at the tie-in edge. Tamko’s starter strips have a specific sealant pattern that must align with the field shingle; misalignment leaves the tab edge free to lift in our spring wind events.
• Cracking or alligatoring on a low-slope ADU roof section. If your ADU has a dead-flat or near-flat section (common on garage conversions in the Old Mountain View neighborhood), standard Heritage shingles were the wrong product from day one. The TW-Drain membrane or a proper low-slope system should have been specified. This is a design error, not a maintenance issue.
• Mold or mildew on the addition’s interior walls, especially at the ceiling corner. This points to a failed vapor barrier or missing ice-and-water shield at the eave-to-wall junction. In Mountain View’s climate, we don’t get ice dams, but we do get wind-driven rain that exploits the same gaps.

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Replacement Cost & What’s Included

For a full addition or ADU roof replacement using Tamko Heritage or Titan XT in Mountain View, installed pricing typically falls within our $45,000-$130,000 range for additions and $90,000-$220,000 for standalone ADUs, with the roof component itself representing 8-14% of that total on a wood-framed structure. A targeted repair, such as membrane replacement at a failed tie-in with new flashing and matching shingles, generally runs $2,800-$6,500 depending on how many courses of existing roofing must be removed to access the failure point.

What drives the range: access (scaffolding or steep-slope rigging), the number of existing layers to remove (Mountain View permits allow two; we often find three on unpermitted additions), and whether the sheathing beneath is sound. Our quote is a flat written price with line-item parts and labor, a written scope, and a written warranty. Under Clause 1 of the Haven Standard, that price is delivered before any work starts. No change proceeds without a signed change order, which is why our projects finish within a few percent of the agreed number. The 365-Day Done Right Promise applies to all roofing and waterproofing work.

DIY or Call Us?

There’s a safe middle ground here. A homeowner can check the attic for active leaks during rain, photograph the shingle condition from a ladder (not the roof itself), and verify the permit status of their addition through Mountain View’s online permit portal. What you should not do: walk a steep addition roof, remove shingles to inspect underlayment, or attempt to heat-weld EPDM membrane. The fall risk on a typical 6:12 addition slope is real, and membrane work requires a clean substrate, proper seam rolling, and edge termination that meets code. We’ve been called to redo DIY membrane jobs where the homeowner used the wrong adhesive and the seam opened in six months. If you’re seeing the symptoms above, call us at (669) 215-4852. We’ll inspect it, photograph what we find, and give you a written price before any work starts.

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