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Therma-Tru Home Additions & ADU: The Dallas Owner’s Guide
If you’re planning a home addition or ADU in Dallas and want Therma-Tru exterior doors on it, the installed cost typically runs $45,000 – $130,000 for the full project, with the Therma-Tru doors themselves accounting for a surprisingly important slice of that budget. We stock and install Therma-Tru-compatible entry, patio, and French door systems that fit both new-construction additions and retrofit ADU work, and we can typically source any Therma-Tru model your architect specified within a few business days. Most homeowners contact us when they’ve discovered that the door they originally bought for a garage conversion or backyard cottage doesn’t actually fit the rough opening, or when a builder-grade door on a newer addition has started sagging in the Dallas heat.
Here’s what most people don’t realize until they’re well into the project: a Therma-Tru door on an addition isn’t just an aesthetic choice. It’s the component that gets the hardest daily use, the most sun exposure on the west-facing wall of a new ADU in Richardson, and the most abuse from foundation settlement that’s common in Blackland Prairie soil. Getting the door spec right before the framing goes up saves thousands in rework later. We’ve seen it enough that we now walk every addition client through the door schedule before we pull permits.
Key takeaways for your Dallas addition or ADU:
- Therma-Tru doors are fully compatible with new-construction additions and ADUs, but the rough opening must be framed to the door’s exact size, not the other way around.
- Plan $1,500 – $4,500 per Therma-Tru door installed, depending on series, glass package, and whether it’s a single, double, or French configuration.
- Dallas heat and clay soil affect door performance more than the door itself, so proper shimming and flashing matter more than the brand.
- We include the Therma-Tru door spec, ordering, and installation in our addition and ADU scope, with a written price before any work starts.
Which Therma-Tru Models This Applies To
Therma-Tru builds its residential door lines around a few core series, and the model you need depends on where the door lives in your addition or ADU. The Classic-Craft series (fiberglass, wood-grain options like Mahogany and Oak) is what we spec most often for front entries on an addition, because it holds a finish for years without warping in Dallas humidity swings. The Smooth-Star series is the workhorse for side doors, back entries, and ADU utility doors, a fiberglass skin over a solid core that takes a coat of paint and shrugs off the summer sun. The Pulse series is the lower-maintenance smooth fiberglass option that many ADU owners choose when they’re trying to keep the overall door budget modest. If you’re doing a rear patio connection on a primary suite addition, that’s typically a Therma-Tru French or sliding patio system, which comes in both hinged French and multi-slide configurations depending on the opening width.
Identifying what you have: the model name is stamped on a label on the door’s hinge edge or top edge, and the size is stamped there too. A standard entry is 3’0″ x 6’8″ (36″ x 80″), but additions and ADUs frequently use 2’8″ x 6’8″ side doors or 5’0″ and 6’0″ double-door configurations. One compatibility gotcha we run into constantly: thermatrue “Standard” series sizing doesn’t always match the old door you’re replacing or the rough opening your framer cut, because Therma-Tru uses true-to-size door slabs, not the nominal sizes common in big-box pre-hung inventory. Measure the actual slab width and height, not the frame. That’s the number that gets you the right door the first time.
OEM versus aftermarket matters here. For Therma-Tru specifically, we almost always recommend OEM slabs and weatherstripping, because the sealing profiles are proprietary. Aftermarket weatherstripping on a Therma-Tru door gets brittle in two Dallas summers and lets air through, which defeats the point of paying for a premium insulated door. For hardware like hinges and multipoint lock bodies, a quality Aftermarket equivalent is often fine, but the door panel itself should be Therma-Tru. Don’t pay premium money and then hamstring it with a generic seal.
Styles & brands we work with
Signs Your Therma-Tru Home Addition or ADU Door Needs Attention
- Door sags or rubs the frame on the latch side. This usually means hinge screws have pulled loose from the jamb, which happens faster in Dallas when the rough opening wasn’t shimmed behind the hinge. A sagging door compounds daily and eventually cracks the frame corner.
- Visible daylight around the weatherstripping. On a new addition, this shows the frame wasn’t squared to the rough opening, or the door was installed before the slab settled. Fixing it properly means re-shimming or adjusting the frame, not just replacing the strip.
- Drafts you can feel with your hand near the threshold. A worn or improperly set Therma-Tru threshold lets hot air in all summer and heated air out all winter. That’s not a comfort problem, it’s an energy bill problem on an addition you already spent real money on.
- Lock mechanism stiff or refusing the key. Dallas’s clay soil shifts, and when a door frame moves slightly, the multipoint lock binds. You’ll feel it before you see it. A binding lock is also a sign the door was installed tight without room for seasonal movement.
- Water stains on the interior wall under the door. This is the one to address the day you see it. A poorly flashed sill pan lets water weep into the subfloor. In a Dallas addition, that subfloor is probably engineered lumber over a crawl space or on-grade slab, and water is its enemy.
See the difference
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AfterReplacement Cost & What’s Included
A Therma-Tru door replacement or new-door install in Dallas runs between $1,500 and $4,500 per door depending on the series, the glass package, and whether it’s a single, double, or French config. When the door is part of a larger home addition or ADU build, that’s nested inside the $45,000 – $130,000 overall project range. For a full ADU, you’re looking at $90,000 – $220,000, and the door package on a two-door ADU is typically $3,000 – $8,000 of that. Here’s the line-item picture for the door portion of the work:
| Therma-Tru Door Item on a Dallas Addition or ADU | Typical Installed Price Range |
|---|---|
| Single entry door (Smooth-Star), painted and installed | $1,500 – $2,400 |
| Single entry door (Classic-Craft), finished and installed | $2,200 – $3,800 |
| Double French doors (patio opening), installed | $3,000 – $4,500 |
| ADU side/utility door, installed | $1,400 – $2,200 |
| Threshold replacement and frame re-shim | $250 – $600 |
What drives the number up or down: frame condition, whether we’re pulling a permit, threshold replacement, sidelight or transom inclusion, and whether the rough opening needs correction (which is common on older Dallas homes in Lakewood or Oak Cliff where the framing has shifted). Every job gets a written price before we touch the opening, and the number on that paper is the number you pay. If the door settles or the seal fails inside 365 days, the Done Right Promise puts us back on site to fix it at no charge.
DIY or Call Us?
You can safely check the label on the hinge edge to confirm your Therma-Tru model and measurements, and you can adjust a sticking latch plate with a screwdriver. What you shouldn’t do is pull the door and frame on a load-bearing wall, especially in an addition where the door is carrying both the header and the roof load above. A door that’s casually “swapped” without proper shimming and flashing is a door that will sag, leak, and bind within a season, and on a Dallas addition that season is usually the first summer. The rough opening correction, flashing, and warranty all go through us. Give you a number before I pick up a tool, that’s the only way we know how to start. Call (940) 204-5368 and we’ll measure it right.
FAQs
A properly installed Therma-Tru fiberglass door lasts 20 to 30 years in Dallas, even with the heat and humidity. What fails first isn’t the slab, it’s the weatherstripping, threshold, and hardware, and all of those are replaceable. The door itself rarely fails before the house needs something else done nearby. Call (940) 204-5368 if you want us to check the seals on an older door before it starts bleeding air.
Yes, in most cases. A sagging door, worn threshold, loose frame, or failed weatherstripping is repairable without replacing the slab. We replace the seal, re-shim the jamb, reset the threshold, and test the lock, typically for $250 – $600. If the slab is cracked or the frame is rotted at the bottom, replacement is the honest call, and we’ll tell you that plainly. Either way, estimates are free.
A single-door replacement takes our crew about four to six hours from removing the old door to cleaning up the site. A double French or patio door set is typically a full day, and a new-construction install during a build is done in phase with the framing. We give you a written arrival window before the job, not after it’s scheduled.
We keep Smooth-Star and Classic-Craft slabs in standard sizes ready to go for jobs around Dallas, and we order custom sizes or special glass packages directly from the Therma-Tru distributor network, typically arriving in three to five business days. We also service and install adjacent trade brands like KraftMaid cabinetry, Cambria and Silestone countertops, so the whole addition envelope is covered by one written guarantee. Call (940) 204-5368 to confirm stock for your exact model and size.
Written by Trevor Nash, Owner, Penhallow Remodeling Dallas at Penhallow Remodeling Dallas, serving Dallas and nearby areas.
