Therma-Tru Home Additions & ADU Nationwide

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

We stock and install Therma-Tru entry systems, sidelites, and patio door units for home additions and ADU projects in San Diego, with typical installed pricing from $53,100 to $153,400 for full addition builds and $106,200 to $259,600 for standalone ADU construction. Most Therma-Tru door and frame replacements within an existing addition scope can be quoted same-day and scheduled within the project sequence. Homeowners usually discover an issue when the fiberglass skin delaminates near the bottom rail after repeated wet-season exposure, or when the composite frame swells enough that the deadbolt no longer throws smoothly - both common in San Diego’s coastal microclimates where morning marine layer keeps moisture against the threshold longer than inland desert conditions.

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Which Therma-Tru Models This Applies To

This guidance covers Therma-Tru’s Classic-Craft, Fiber-Classic, Smooth-Star, and Pulse series lines, which are the four systems we most often spec into San Diego additions and ADUs. Classic-Craft uses a hardwood edge with a fiberglass skin; Fiber-Classic is all-fiberglass with a wood-grain emboss; Smooth-Star is the paint-ready smooth surface; Pulse is the contemporary flush-panel design. The critical compatibility gotcha is the jamb width: Therma-Tru ships standard with 4-9/16″ jambs for 2×4 framing, but San Diego additions built after 2018 often use 2×6 walls for Title 24 energy compliance, requiring the 6-9/16″ jamb option or a factory-ordered extension kit. The model number is stamped on the hinge edge of the door slab, usually above the top hinge, and begins with the series prefix (CC, FC, SM, or PL) followed by the size code.

We source OEM Therma-Tru components through their authorized distribution network, though for certain ADU projects where the original unit is discontinued, we also vet aftermarket fiberglass door systems from Plastpro and JELD-WEN that match the rough opening and hardware prep without requiring frame modification. The OEM versus aftermarket decision usually comes down to whether the existing frame is salvageable: if the composite jamb legs are sound, we can often retrofit a new slab with matching hinge mortises and bore prep, which saves roughly $400 to $700 in material and labor versus full unit replacement.

Signs Your Therma-Tru Home Additions & ADU Is Failing

• Bottom rail saturation and delamination. The fiberglass skin separates from the polyurethane core near the sweep, creating a soft spot you can press with a thumb. In San Diego, this happens most often on north-facing additions in Point Loma and La Jolla where the marine layer lingers past 10 a.m. and the threshold never fully dries.
• Frame swelling at the lock stile. The composite jamb expands enough that the deadbolt or latch binds against the strike plate. We see this on Smooth-Star units more than Classic-Craft because the smooth skin offers less mechanical bond to the core, allowing moisture ingress at the corner seams.
• Sidelite seal failure with visible fogging. The insulated glass unit between the door and sidelite loses its argon fill, showing condensation you cannot wipe from either side. On south-facing ADUs in Clairemont and Kearny Mesa, UV exposure accelerates the butyl seal degradation to roughly 8 to 12 years instead of the 15-year design spec.
• Threshold cap separation from the subsill. The aluminum or composite cap lifts at the ends, creating a trip hazard and water path into the subfloor. This is almost always installation-related: the cap was not bedded in sealant or the fasteners missed the subsill blocking.
• Corner pad deterioration on outswing units. The composite corner pads that protect the hinge and lock stile bottom corners crumble after repeated wet-dry cycling. Outswing doors are required for certain ADU configurations under San Diego’s fire separation code, so this is a compliance issue as well as an aesthetic one.

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Replacement Cost & What’s Included

The range depends on three factors: jamb width and whether factory extensions are needed; hardware prep (Therma-Tru’s standard bore is 2-1/8″ with a 5-1/2″ center-to-center for handlesets, but some older units use 5-3/4″ which requires a new prep or adapter plate); and whether the interior trim package is included or owner-supplied. Every replacement quote from Rowan Construction Group San Diego is a flat written price with line-item scope, delivered before any work starts. Under Clause 1 of The Haven Standard, that written price is fixed: no change proceeds without a signed change order, which is the discipline that has kept our projects within a few percent of the agreed cost across 4,000-plus jobs since 2007. The 365-Day Done Right Promise covers installation and hardware function; the Therma-Tru limited lifetime warranty covers the door slab itself against delamination and warp.

DIY or Call Us?

There is one safe owner check: open the door to 90 degrees, crouch at the hinge edge, and look for the stamped model number. If you photograph that and the failure symptom, we can often spec the replacement before the site visit. What goes wrong with DIY is everything after that. Fiberglass door slabs weigh 80 to 120 pounds depending on size and glass lite, and the hinge mortises must be cut to 1/8″ tolerance or the door will bind in summer and leak in winter. More critically, if the unit is part of a rated separation between the primary dwelling and an ADU - common under San Diego’s municipal code for fire safety - replacement requires permit verification and often an inspection. The threshold cap replacement looks simple but the subsill must be checked for rot; we have opened units in Pacific Beach where the cap appeared intact but the OSB subfloor beneath was punky to six inches back. Measure twice, document once, then we can talk price. For a written quote with photo documentation included as standard, call (858) 434-8926.

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