Therma-Tru Home Additions & ADU Nationwide

Therma-Tru Home Additions & ADU: The Redwood City Owner’s Guide

Therma-Tru entry systems in Redwood City home additions and ADUs typically run $45,000-$130,000 for full addition projects incorporating these doors, with Therma-Tru door-specific replacements and integrations starting around $2,800-$7,500 installed. We stock Therma-Tru Classic-Craft, Smooth-Star, and Fiber-Classic series components for same-day assessment on most calls. Most Redwood City owners discover an issue when the fiberglass skin delaminates near the threshold, the door slab warps in the Peninsula’s marine air, or the multi-point locking system seizes after years of salt-laden fog cycling through Stambaugh-Heller and the flatlands toward the bay.

Call (650) 560-7228

Which Therma-Tru Models This Applies To

Therma-Tru organizes its residential lines by substrate and skin type, and the right integration depends on which series was originally specified for your addition or ADU.

Classic-Craft carries an oak-grain fiberglass skin over a polyurethane core; look for the embossed “Classic-Craft” stamp on the hinge edge and a model prefix beginning CCA, CCB, or CCM. These doors weigh 40-60% more than steel equivalents, so framing must be verified before any replacement or re-hanging.

Smooth-Star has a primed, paint-ready fiberglass surface with no grain embossing. Model codes start SS. These are common in Redwood City ADUs where owners want a custom color match to the main house. The smooth skin shows dents more readily but resists the moisture swelling that destroys steel doors in our climate.

Fiber-Classic is the original Therma-Tru line, still specified for Craftsman-style additions in neighborhoods like Stambaugh-Heller where historical texture matters. Model prefix FC.

The critical compatibility gotcha: Therma-Tru’s multi-point locking hardware is series-specific. A Classic-Craft mortise lockset will not seat in a Smooth-Star prep without jamb modification, and the backset dimensions differ between pre-2012 and current production. We carry both eras of hardware on our trucks. OEM parts maintain warranty compliance; quality aftermarket equivalents from Emtek or Baldwin meet the same ANSI Grade 2 standard at roughly 15-20% lower cost. We quote both and let the owner decide.

Signs Your Therma-Tru Home Addition or ADU Door Is Failing

• Fiberglass skin bubbling or separating at the bottom rail. This is water wicking up through the end grain of the composite stile, then freezing against the skin in our January cold snaps. Once delamination starts, the structural core absorbs moisture and the door gains weight, stressing hinges and throwing off the reveal.
• Multi-point lock handle rotates but deadbolts don’t extend. The internal rods connecting the handle hub to the top and bottom shootbolts have slipped their guides, usually from house settling or repeated slamming in a tight ADU where airflow pressurizes the slab. The lock mechanism itself is fine; the linkage needs realignment or replacement.
• Door sticks seasonally, worst in October and April. Redwood City’s marine layer swells the jamb more than the fiberglass slab, pinching the strike side. This is framing movement, not door failure, but left unaddressed it warps the hinge mortises and cracks the fiberglass skin at the corner.
• Threshold cap is cracked or the adjustable riser no longer seals. The aluminum threshold extrusion outlasts the vinyl or composite cap by a decade. Water runs under the door, saturates the subfloor, and the first sign is a spongy feel at the interior landing. In ADUs over crawl spaces, this goes unnoticed until joist damage is extensive.
• Glass lite fogging between panes on door with inserts. The IGU seal has failed. Therma-Tru sources these from multiple vendors, and the spacer bar profile changed in 2015. Matching the glazing bead profile is the difference between a $340 glass swap and a $2,100 full-lite door replacement.

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Replacement Cost & What’s Included

These numbers include removal and disposal, rough-opening inspection and repair as needed, new Therma-Tru-compatible components, installation with shimming and foam insulation, hardware adjustment, and weatherstrip sealing. What drives the range: whether the existing frame is plumb and square (many Redwood City additions from the 1970s-1990s are not), whether the threshold subfloor needs sistering or replacement, and whether we are matching a discontinued grain pattern or lite shape. Under Clause 1 of the Haven Standard, you receive a written price before any work starts. The 365-Day Done Right Promise covers installation and hardware function. Call (650) 560-7228 for a written estimate.

DIY or Call Us?

There’s a safe middle ground here, and a hard stop.

An owner can verify the model series from the hinge-edge stamp, photograph any delamination or threshold damage for our review, and check whether the door closes against the weatherstrip without visible gaps. A flashlight test from the exterior at night reveals seal failure quickly.

Where DIY goes wrong: Therma-Tru fiberglass doors are rigid but brittle at the corners; lifting a slab without supporting the lock stile cracks the skin. The multi-point lock mechanism is under spring tension; disassembly without the correct release sequence bends the internal rods. And any door in an ADU or addition must meet current California Title 24 energy standards and local fire separation requirements if the ADU is attached, which means permit verification before replacement. We pull permits as standard, include the documented photo record of rough and final conditions, and schedule inspection. For a door that sees daily use and secures a space you live in, the cost of a failed self-install usually exceeds the original professional quote.

Call (650) 560-7228 to schedule your free estimate.

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