Therma-Tru Home Additions & ADU Nationwide

Therma-Tru Home Additions & ADU: The San Jose Owner’s Guide

Therma-Tru entry systems in San Jose home additions and ADUs typically run $53,100-$153,400 installed, depending on whether you’re integrating a single door into a bump-out or designing a full accessory dwelling unit with multiple entry points. We stock Therma-Tru-compatible frames, sills, and jamb components for same-day replacement when the existing unit has failed. Most San Jose owners discover the problem during the final inspection walkthrough, when a door that passed rough-in now binds, leaks, or shows daylight at the weatherstrip after the addition has settled.

Call (669) 271-8644

Which Therma-Tru Models This Applies To

Therma-Tru organizes its residential lines by material and exposure rating, and the part you need depends on which series was specified in the original addition plans. The Classic-Craft and Fiber-Classic collections use a proprietary composite jamb system with a 4-9/16″ standard width and an adjustable composite sill cap, while the Smooth-Star and Profiles lines run a 6-9/16″ jamb for 2×6 framing common in ADU energy-code builds. Check the hinge-side label for a nine-digit SKU starting with “C” for Classic-Craft or “S” for Smooth-Star; the last four digits indicate the factory bore and handing configuration.

We carry OEM jambs, sills, and weatherstrip kits for all four series, plus an aftermarket adjustable sill from Endura that matches Therma-Tru’s drainage geometry and exceeds the CA moisture-exposure spec. The aftermarket route saves roughly 20% on material, but we flag this: Classic-Craft doors with the Cherry or Mahogany grain require the OEM jamb to maintain the factory warranty on the skin delamination coverage. Mixing series is the gotcha we see most often in San Jose, where a Smooth-Star slab gets hung on a Fiber-Classic jamb and the screw bosses don’t align, leaving the strike side loose within two seasons of thermal cycling.

Signs Your Therma-Tru Home Additions & ADU Is Failing

• Visible daylight under the door when closed. The composite sill cap has compressed or cracked, common in San Jose where south-facing ADU entries see 180+ days of direct sun. The cap is replaceable independently of the full jamb if caught before the subsill rots.
• Door binds at the top corner opposite the hinges. The addition has settled or the header has deflected, twisting the jamb out of square. We measure with a 6-foot level; anything past 1/8″ in 3 feet means the jamb needs re-shimming or replacement, not just planing the door.
• Water staining on the interior trim after rain. The weatherstrip bulb has lost compression set or the corner pads have shifted. Therma-Tru’s Q-Lon foam weatherstrip degrades faster within 3 miles of the bay where salt air accelerates the breakdown.
• Lockset latch misses the strike plate. The hinge screws have backed out of the composite jamb, or the jamb itself has split at the screw pattern. This is structural; a longer screw into framing only masks the jamb damage.
• Exterior skin delamination or bubbling. Moisture intrusion at the sill or mull joint has reached the fiberglass substrate. On Classic-Craft and Fiber-Classic, this is warranty-eligible if the OEM jamb and sill were used and the installation documentation is intact.

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After

Replacement Cost & What’s Included

The spread reflects three variables: whether the existing opening needs reframing to current Title 24 energy code, whether the stucco or siding integration requires matching, and whether the original door was a standard size or a custom height common in Willow Glen and Almaden Valley builds from 2015-2020. Our quote is a flat written price with line-item parts and labor, signed before work starts. Under Clause 1 of the Haven Standard, that number does not change unless you sign a change order. Every Therma-Tru installation carries our 365-Day Done Right Promise and the manufacturer’s warranty, documented in the photo record you receive at completion.

DIY or Call Us?

There’s a safe middle ground here. A homeowner can verify the model from the hinge label, photograph the failure, and check the sill cap for debris blocking the weep holes, which is the cause of half the “leaks” we see in San Jose. What goes wrong past that point: the composite jamb requires a dead-blow hammer and specialized spreader bars to remove without splitting the stucco return, and the adjustable sill must be set to the exact threshold height before the door is hung, not shimmed afterward. We’ve rebuilt three DIY attempts in the past eighteen months where the owner drove structural screws through the thermal break, voiding the energy cert and creating a condensation path. If the door weighs more than you can shoulder comfortably, or if the addition is under active permit with a pending final, call (669) 271-8644. We’ll give you a written price and a timeline, and we pull the permit amendment if the inspector wants to see the installation certificate.

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