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Therma-Tru Home Additions & ADU: The San Antonio Owner’s Guide
A Therma-Tru home addition or ADU project in San Antonio typically runs $45,000 to $130,000 for the addition itself, and $90,000 to $220,000 for a full ADU with a kitchen and bath. What surprises most owners isn’t the framing or the roof line, it’s how quickly the door and window choices affect the whole build. You find this page because you’ve already committed to a Therma-Tru product somewhere in the plan, and now you’re trying to figure out whether it’s the right call for the addition, how it holds up to San Antonio heat, and what it actually costs to get it installed correctly. Here’s the answer, written down the way Graham Stein writes every scope before a single tool leaves the truck.
Most people discover a problem mid-project, not at the start. They order a Therma-Tru door for the new wing, the rough opening doesn’t match what the plan said, or the ADU’s back door sits on the west side and bakes from 2 p.m. until sunset from June through September. That’s when the phone call happens. We’ve already been on-site in neighborhoods from Alamo Heights to Stone Oak, so we know what the conditions actually are before the door ever arrives.
Which Therma-Tru Models This Applies To
Therma-Tru makes entry doors, patio doors, and sidelite systems across several lines: the Classic-Craft, Fiber-Classic, Smooth-Star, and Pulse series all show up frequently in San Antonio home additions and ADU projects. The Fiber-Classic and Classic-Craft lines hold up best on west-facing elevations because the fiberglass skin doesn’t warp the way some wood stile-and-rail doors do after three or four Texas summers. The Smooth-Star series costs less and performs fine on covered entries, but we steer clients away from it for unshaded south or west exposures where the door takes direct sun for six hours a day.
The compatibility gotcha most owners hit is the rough opening. Therma-Tru doors in the Classic-Craft line specify a rough opening that runs slightly taller than a standard big-box door of the same nominal size, so if the framing was done for a generic 36×80, the Therma-Tru unit may need the header adjusted. That’s a framing fix, not a door fix, and it’s cheaper to catch before the drywall goes up. Always have the exact Therma-Tru part number, which sits on a label on the hinge edge of the slab and on the packaging. Elmstead Remodeling San Antonio is an independent contractor and not affiliated with Therma-Tru, but we order directly from authorized distributors so the warranty paperwork stays valid. As for OEM versus aftermarket: with Therma-Tru, we recommend OEM weatherstripping and sill components. The aftermarket equivalents work, but the compression seal on a Therma-Tru sill is a specific durometer, and the generic versions let dust and hot air seep in around a San Antonio home addition faster than you’d expect.
Styles & brands we work with
Signs Your Therma-Tru Home Additions & ADU Is Failing
- Door binds at the latch in the afternoon. The slab expands slightly in heat, and if the reveal was set too tight, it catches. Cause: the door was hung without accounting for San Antonio’s diurnal temperature swing. The fix is a hinge adjustment or slab edge shave, not a new door.
- Dust lines inside the sill track. If you can see a crescent of fine grit along the interior sill after a windy day, the bottom sweep isn’t compressing against the adjustable sill. Cause: the sill cap was set once and never re-checked after the slab settled, common in new additions where the subfloor shrinks in the first six months.
- West-side door too hot to touch on the inside face. That’s direct solar gain conducting through the slab. Cause: a dark-painted fiberglass door on an unshaded west wall in August. The door isn’t failing, but the paint finish will start to chalk and hairline over time without a storm door or awning.
- Sound comes through the threshold like a gap. You hear the neighbor’s dog or the street clearly at floor level. Cause: the adjustable oak sill was never set to full contact after final floor finish. Ten minutes with a hex key gets it right if you catch it before the weatherstrip gets permanently crushed.
- Sidelite glass fogs between panes. Insulated glass seal failure. Cause: years of thermal cycling, and San Antonio’s mix of hot afternoons and cool overnights speeds it up. The glass panel gets replaced, not the whole sidelite frame.
See the difference
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After
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AfterReplacement Cost & What’s Included
When the Therma-Tru product is part of a larger home addition, the door or window work typically runs $2,000 to $7,000 of the overall $45,000 – $130,000 addition budget, depending on how many units and whether we’re dealing with an entry system, sidelites, or a patio door. A full ADU with Therma-Tru entry and patio doors falls inside the $90,000 – $220,000 range, with the door package rarely exceeding 8% of the total. If we’re swapping a single existing Therma-Tru door rather than building new, you’re looking at $1,800 to $5,500 installed in San Antonio, with the spread driven by whether the rough opening needs reframing, whether the door is a standard 36×80 or a custom unit, and whether the sill pan needs to be replaced when the old door comes out.
Every line item is written before work starts, the way Graham Stein does every project. The written price you sign is the price you pay. No charges added after demolition day. The work carries the 365-Day Done Right Promise: if it’s not done right after the job is complete, we make it right. The Therma-Tru manufacturer warranty applies to the door itself, and our installers set the sill, shim the jambs, and adjust the sweep so the warranty isn’t voided by poor installation.
DIY or Call Us?
A Therma-Tru door on a home addition or ADU is not a dangerous part, but it is a heavy one. A Classic-Craft entry unit with sidelites can weigh over 300 pounds, and a patio slider is more. What an owner can safely check: the reveal lines around the slab, whether the sill cap screws are snug, and whether the weatherstrip is still pliable. What goes wrong when a homeowner tries to swap a Therma-Tru unit without experience: the rough opening gets out of square, the sill pan flashes incorrectly, and water finds the subfloor inside the first year. We’ve repaired several homeowner-hung doors in San Antonio where the first rain after the install pushed water under the sill and into the new ADU’s laminate floor. That repair costs more than the original install would have. Call (432) 233-0976 and we’ll measure, order, and hang it once.
FAQs
A properly installed Therma-Tru fiberglass entry door lasts 25 to 35 years in San Antonio, though the weatherstripping and sill cap typically need replacement every 7 to 10 years from sun and heat exposure. Call (432) 233-0976 and we’ll tell you whether you need a $40 part or a new slab.
Yes, most issues are repairable: hinge adjustments, sill cap replacement, sweep replacement, glass unit swaps, and reflashing are all standard fixes we do on Therma-Tru products here in San Antonio. Replacement only makes sense when the slab itself is cracked or the frame has water damage.
A single entry door swap takes one day including the sill pan, trim, and hardware. A full entry system with sidelites and a transom runs two days, and a patio door replacement on an ADU runs one to two days depending on the rough opening. Ask (432) 233-0976 for the written time window before we start.
We keep sweep seals, compression weatherstripping, astragal components, and sill caps for the most common Therma-Tru models on our trucks, and we order door-specific components direct from authorized distributors, same as we do for the KraftMaid, Cambria, and Silestone materials we work with on other San Antonio jobs.
Key Takeaways
- Therma-Tru additions and ADUs in San Antonio run $45,000 – $130,000 for additions and $90,000 – $220,000 for full ADUs, with door packages typically 3-8% of total cost.
- West-facing Therma-Tru doors need shade or light colors; dark fiberglass slabs on unshaded walls heat up fast here.
- Most Therma-Tru failures are repairable adjustments, not replace-the-door situations.
- Elmstead Remodeling San Antonio writes every price down before work starts, and the 365-Day Done Right Promise covers every completed project.
If you’re planning a home addition or ADU in San Antonio and the Therma-Tru door choice matters to you, call Elmstead Remodeling San Antonio at (432) 233-0976 to schedule your free estimate. Write it down, price it once, do it right.
Written by Graham Stein, Owner, Elmstead Remodeling San Antonio at Elmstead Remodeling San Antonio, serving San Antonio and nearby areas.
