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Therma-Tru Home Additions & ADU: The San Antonio Owner’s Guide
If you’re planning a home addition or ADU in San Antonio and want Therma-Tru doors and entry systems specified throughout, a full addition runs $45,000 to $130,000 while a detached ADU typically lands between $90,000 and $220,000. The Therma-Tru components themselves, fiberglass and steel entry doors, sidelights, and transoms, are one of the smartest line items in that budget because they hold up to San Antonio’s UV load and humidity swings better than wood. Most homeowners call us when they’re mid-plan and realize their builder’s “standard door allowance” won’t cover the Therma-Tru spec they actually want, or they’re adding square footage and the existing entry no longer matches the scale of the new build.
Key Takeaways:
- A Therma-Tru entry system in a San Antonio addition costs $700 to $4,500 installed depending on doors, sidelights, and finish level
- Therma-Tru’s fiberglass doors don’t warp or swell the way wood doors do in San Antonio humidity cycles
- We install and service Therma-Tru systems on every addition and ADU we build; we’re an independent contractor, not a Therma-Tru dealer
- Written pricing before work starts means your door budget and your framing budget never surprise you
We’re Sawyer Remodel San Antonio, part of the Relay Home Co. family since 2005. Luca Romano runs our local operation, and he still walks every finished addition himself before we hand over keys. The craft comes first. Everything else follows.
Which Therma-Tru Models This Applies To
Therma-Tru’s current lineup breaks into a few series that show up constantly in San Antonio additions: the Classic-Craft fiberglass line, the Smooth-Star line, the Pulse series (their composite wood-look doors), and the Benchmark entry system line for ADUs and smaller budget-conscious builds. If your addition has a covered front porch or deep overhang, a Classic-Craft Mahogany grain door in a 6’8″ or 8′ height is common. If the entry faces full west sun, we spec Smooth-Star or Classic-Craft with a UV-stable finish rather than painted wood-grain fiberglass, which will chalk faster.
The fastest way to identify your Therma-Tru model: open the door and look at the hinge edge of the slab. Therma-Tru stamps a manufacturer code and manufacturing date there, usually within 12 inches of the bottom. If the label is gone or painted over, measure the slab thickness (1-3/4″ is standard for Therma-Tru entries), the rough opening width, and whether you have a single door, a door with one sidelight, or a door with two sidelights. That measurement set gets us 90% of the way to the right replacement or new install. For ADU builds, many San Antonio owners go with Therma-Tru’s 6’8″ or 7′ smooth fiberglass doors (a bit over 6 foot 8 inches) since ADU entries are often narrower, and Therma-Tru makes doors in 30″, 32″, and 36″ widths that fit those tighter lots.
On OEM versus aftermarket: for the door slab, sidelight glass, weatherstripping, and adjustable sills, we always recommend Therma-Tru OEM. Their weatherstripping is a specific profile that doesn’t match generics, and using a knockoff causes air leaks and condensation at the threshold. For hinges and multipoint lock hardware, we’ll happily use quality aftermarket options (Emtek, Baldwin) because they’re often more durable than the entry-level builder hardware some Therma-Tru packages ship with.
Styles & brands we work with
Signs Your Therma-Tru Home Additions & ADU Is Failing
- The door drags or sticks in winter but swings fine in summer. San Antonio’s clay-heavy soil shifts with moisture, and the slab under a new addition can move fractions of an inch in the first two years. You’ll see rub marks at the top corner of the door or the latch no longer lines up with the strike plate. The door probably isn’t warped; the rough opening settled.
- You feel a draft or see daylight at the bottom corners. The Therma-Tru adjustable sill has a plastic cap and compression gasket that degrades under direct sun. Once the gasket hardens, air moves under the door. We see this most on west-facing entries in neighborhoods like Alamo Ranch and Stone Oak where afternoon heat is relentless.
- Condensation fogs between the glass panes of a sidelight or the door’s decorative glass. The sealed glass unit has lost its argon fill or the desiccant inside the spacer has saturated. It won’t clear up on its own, and the glass gets cloudy worse every season. This is covered under Therma-Tru’s glass warranty for a set period, but aging units fail eventually.
- The multipoint lock only throws one point, or you have to lift the handle to get it to engage. The gearbox inside the multipoint lock wears down, especially if the door was slightly misaligned for months before you noticed. A worn gearbox means the deadbolt and upper/lower shootbolts don’t fully seat, which is a security issue on an ADU entry.
- Therma-Tru fiberglass skin is cracking or the finish is chalking badly. A small surface crack in the skin can let water wick into the foam core. In San Antonio, our freeze-thaw cycles are mild, but the summer monsoon season plus full sun can turn a small crack into a peeling finish and core damage within two years.
See the difference
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After
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AfterReplacement Cost & What’s Included
Here’s what you should expect to pay in San Antonio for common Therma-Tru work on an addition or ADU:
- Full Therma-Tru entry door replacement (single door, one sidelight, basic finish): $2,000 to $4,500 installed
- Therma-Tru door slab only (no frame), standard 3’0″ x 6’8″: $700 to $1,400 installed
- Therma-Tru replacement glass insert for a 22″ x 64″ decorative glass door: $350 to $900 installed
- Adjustable sill cap and weatherstripping replacement: $150 to $400 installed
- Multipoint lock gearbox and hardware replacement: $300 to $700 installed
Labor in San Antonio runs from $85 to $150 per hour for finished carpentry work, and a door swap with minor drywall or stucco touch-up at the interior trim is usually a four to six hour job. We give you a written line-item price before a single tool gets picked up. That price includes the door, hardware, installation, the haul-away of your old unit, and our 365-Day Done Right Promise in writing: if it’s not done right, we make it right. No change orders unless you change the scope.
DIY or Call Us?
There are a few things you can safely check yourself. Walk around and see if the reveal is even on the sides. Apply a dollar bill test on the weatherstripping at the bottom corners. If the bill slips out with no resistance, your gasket is shot, and that’s a simple part order. If the hinges are loose, a #2 Phillips driver and two minutes gets you back to square. But once you’re into pulling a 150-pound fiberglass door off its hinges, shimming a rough opening, or getting into multipoint lock internals, the downside is real: a dropped door takes out drywall (best case) or a toe (worse), and a mis-shimmed door will never seal right in San Antonio’s summer humidity. The fiberglass slab itself is not an amateur repair. Call us at (432) 547-6806 and we’ll quote the job, show up on time, and photograph the work before and after.
FAQs
Expect 20 to 30 years from the fiberglass slab and 8 to 15 years from the weatherstripping, glass sealed units, and finish, because San Antonio’s sun and humidity cycles wear the exterior parts faster than the door itself. When the hardware or weatherseal goes, you’re replacing a component, not the door. Call (432) 547-6806 and we’ll tell you which one it is before you spend anything.
Yes, in most cases. A drafty threshold, blown glass insert, worn weatherstripping, or failed multipoint gearbox are all component-level repairs that cost a few hundred dollars, not a full replacement. The only time we push replacement is when the fiberglass skin is cracked through or the door was installed wrong initially and has been fighting the frame for years.
For a standard single entry door with one sidelight, we finish in one day, usually five to six hours from tear-out to final walkthrough. A custom door or one tied into new stucco work on an addition might take a second visit for exterior trim and paint. You’ll have the written timeline before we start.
We keep the common wear items on our trucks: adjustable sill caps, weatherstripping, multipoint lock gearboxes, and glass inserts in the most common San Antonio sizes. If we don’t have your exact glass lite or slab, we order direct and install within one to two weeks depending on Therma-Tru’s build queue.
If you’re planning an addition or ADU in San Antonio and want Therma-Tru doors spec’d, installed, or repaired correctly, call (432) 547-6806 for a free estimate. We’ll give you a written price, a real arrival time, and photo updates before and after the work. We also work with KraftMaid cabinetry, Cambria and Silestone countertops, and Kohler fixtures across the rest of your project.
Written by Luca Romano, Owner, Sawyer Remodel San Antonio at Sawyer Remodel San Antonio, serving San Antonio and nearby areas.
