Therma-Tru Home Additions & ADU Nationwide

Therma-Tru Home Additions & ADU: The Walnut Creek Owner’s Guide

Therma-Tru entry systems in Walnut Creek home additions and ADUs typically run $45,000-$130,000 installed, depending on whether you’re integrating a single door into a bump-out or building a full detached unit with multiple access points. We stock Therma-Tru Classic-Craft, Smooth-Star, and Fiber-Classic series frames, sills, and jamb components for same-day replacement when the original unit has shifted, rotted, or lost its weather seal. Most Walnut Creek owners discover the problem after the first heavy winter rain, when water pools at the threshold or the door sticks in the jamb.

Call (510) 686-6370

Which Therma-Tru Models This Applies To

Therma-Tru organizes its residential lines by substrate and skin, and the right replacement part depends on which series was originally specified. Classic-Craft uses a polyurethane core with an oak-grain fiberglass skin and accepts stain or paint; Smooth-Star is paint-only with a smooth skin over the same core; Fiber-Classic was the original fiberglass door line, now largely superseded but still present in Walnut Creek homes built between 1995 and 2010. The part number is stamped into the hinge edge of the door slab and on a foil label inside the frame head. For ADU applications, we see two common gotchas: the 6/8 door height in older Fiber-Classic units doesn’t always align with modern 6/9 rough openings without jamb modification, and the composite sill in pre-2012 Smooth-Star units used a different drainage geometry than current production. We carry both the OEM Therma-Tru replacement sills and the Endura Z-Series equivalent, which matches the footprint but upgrades the composite to a more stable mineral formulation. Our written quote names the exact part before we order.

Signs Your Therma-Tru Home Additions & ADU Is Failing

• Water staining at the base of the jamb. The composite sill capillary seal has cracked or the end-seals have pulled away, letting Walnut Creek’s winter-driven rain wick up the jamb legs. Left alone, the MDF jamb core swells and the door binds.
• Door sticks seasonally but not year-round. The frame was fastened without shimming at the sill, so the slab drops in dry months and rubs the head in wet ones. This is framing movement, not door failure, but it destroys the weatherstrip compression.
• Visible daylight under the closed door. The adjustable threshold insert has worn below the seal line or the sweep has hardened. Therma-Tru thresholds are adjustable with a Phillips driver; if the insert is bottomed out and still leaking, replacement is the only fix.
• Fiberglass skin delamination at the bottom rail. Standing water on an unprotected stoop attacks the bond line. The skin lifts, water enters the core, and the door gains weight until the hinges pull.
• Lockset misalignment that worsens over weeks. The strike plate no longer meets the latch cleanly because the frame has racked. In ADU conversions, we see this where the original garage slab has settled and the prehung frame has twisted with it.

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Replacement Cost & What’s Included

These are installed prices with haul-away of the old unit, new composite shims, and low-expansion foam seal. What drives the range is jamb width (4-9/16″ standard in Walnut Creek, 6-9/16″ for 2×6 walls), whether the brickmold needs replacement, and if the opening has racked beyond 1/4″ out of square. Under Clause 1 of The Haven Standard, the written price you receive is the price you pay; no change proceeds without a signed change order. Our 365-Day Done Right Promise covers the installation and the seal performance.

DIY or Call Us?

There’s a safe middle ground. You can check the threshold adjustment yourself: open the door, look for the two Phillips screws in the top of the aluminum saddle, and turn them to raise or lower the seal against the sweep. If that stops the leak, you’ve solved a $12 problem. What you should not attempt is pulling a prehung unit from a load-bearing opening. The header above a 3/0 door in an ADU carries roof or second-floor load; remove the frame without temporary support and the structure settles. We also don’t recommend slab-only swaps for fiberglass doors; the hinge mortises are machine-cut at the factory to 0.005″ tolerance, and hand-routing in the field almost always leaves the door hanging heavy or binding. Call (510) 686-6370 and we’ll measure, quote in writing, and schedule the replacement.

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