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Therma-Tru Home Additions & ADU: The Los Angeles Owner’s Guide
Adding square footage with a Therma-Tru door package as your entry point typically runs $53,100 – $153,400 for a home addition in Los Angeles, while a full ADU build starts around $106,200 and can reach $259,600 depending on size and foundation work. We stock Therma-Tru-compatible hinges, thresholds, weatherstripping, and frame components on our trucks, and we install door systems as part of larger addition and ADU projects every week across Los Angeles County. Most Los Angeles homeowners discover their Therma-Tru component has failed when the door starts dragging, water pools inside the threshold after a winter rain, or the frame shifts and the latch no longer lines up. That’s usually the moment they call us, holding the door open with one hand and their phone in the other.
Here’s the part nobody mentions until it happens: your Therma-Tru door is only as good as the rough opening behind it, and in Los Angeles, that opening moves. Clay soil expands and contracts through our wet-dry cycles, and additions built on perimeter foundations settle differently than the original house. The door takes the brunt of that movement first.
Key Takeaways:
- Therma-Tru parts are model-specific, but most components cross-reference by door thickness, hinge radius, and sill profile.
- Installed replacement work on Therma-Tru doors within a larger addition or ADU project in Los Angeles typically lands between $470 and $2,950 for the door component itself, with full door system replacement falling in the $5,310 – $17,700 range when framing and finish work are included.
- Every Mason Remodeling Co Los Angeles project gets a written price before any work starts, and every crew member arrives with name, photo, badge, and uniform verified through the Threshold Standard.
Which Therma-Tru Models This Applies To
Therma-Tru builds entry systems across three broad families: the Classic-Craft line (their fiberglass flagship, known for deep wood-grain textures), the Smooth-Star series (a clean-face fiberglass at a lower price point), and the Pulse line (mid-tier with a wider color range). Each family uses its own hinge prep, sill geometry, and weatherstrip profile. The gotcha we run into constantly in Los Angeles: a Sweepstrip bottom seal from a Smooth-Star will not fit a Classic-Craft sill, even if both doors are 3’0″ x 6’8″. The sill cap lip height differs by about a quarter inch, and forcing the wrong sweep chews through it in a season.
If you’re trying to identify what you have, look at the hinge edge of the door slab. Therma-Tru stamps a manufacturing code near the bottom, usually a combination of letters and numbers. The first two characters identify the plant, the next cluster the series. Snap a photo of that stamp and the sill profile before you call, because a five-minute photo saves a parts return trip across Los Angeles traffic. For mid-2000s installs, the stamp may be worn off, in which case the hinge corner radius (Therma-Tru uses a 5/8″ radius on most residential pre-hungs) and the weatherstrip channel depth usually tell us what we’re dealing with.
On the OEM versus aftermarket question: for seals, sweeps, and thresholds, quality aftermarket equivalents from brands like Pemko or M-D Building Products perform equal to Therma-Tru OEM in most Los Angeles installations and cost 20 – 40% less. For structural parts (hinges with the Therma-Tru alignment pin, the multi-point lock assembly on Classic-Craft models), we recommend OEM. The aftermarket copies of those locks have looser tolerances, and on a heavy fiberglass slab, that translates to binding within a year.
Mason Remodeling Co Los Angeles is an independent contractor and is not affiliated with Therma-Tru. We install Therma-Tru-compatible components because Los Angeles homeowners already own these doors and they deserve fast, honest service on them.
Styles & brands we work with
Signs Your Therma-Tru Home Additions & ADU Door Is Failing
- Water pooling inside the threshold after rain. Los Angeles gets maybe 15 inches of rain a year, but when it comes, it finds every failed sill cap. The plastic cap on Therma-Tru sills cracks with UV exposure (we see it in south-facing entries in Woodland Hills and Sherman Oaks constantly), and water tracks under the door into your flooring.
- The latch bolt no longer lines up with the strike plate. This is a frame issue, not a lock issue. In additions and ADUs, the subfloor or rim joist has settled or the rough opening wasn’t shimmed correctly. The door slab may be perfectly fine, but the opening has moved around it.
- Visible light around the perimeter when the door is closed. Weatherstripping has compressed or the frame has racked. Either way, you’re losing conditioned air into a Los Angeles summer that already runs the AC hard.
- Drag marks or wear lines on the sill. The door has dropped. On a Therma-Tru, that’s usually one of three things: a worn hinge bearing, a frame hinge that’s pulling loose from the jack stud, or a slab that wasn’t balanced when it was hung. The longer it drags, the more the sill cap wears down and the more likely you’re replacing the whole sill assembly instead of a hinge.
- Door doesn’t close without a shove, then closes fine on cooler days. Fiberglass expands in heat. Los Angeles afternoon sun on a west-facing door can grow the slab enough to catch on the sweep. That tells us the reveal was too tight at installation, and the fix is usually a hinge adjustment plus new weatherstrip, not a new door.
See the difference
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After
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AfterReplacement Cost & What’s Included
For Therma-Tru door component work tied to a home addition or ADU in Los Angeles, plan on these installed ranges:
| Service | Installed Price Range (Los Angeles) |
|---|---|
| Weatherstrip / sweep replacement | $470 – $2,125 |
| Threshold / sill cap replacement | $710 – $2,950 |
| Full entry door system replacement (in-frame) | $5,310 – $17,700 |
| Home addition (complete scope) | $53,100 – $153,400 |
| ADU construction (full build) | $106,200 – $259,600 |
What drives the spread on the small parts is framing condition. If the hinge screws pull out because the jack stud is rotted, that’s a different job than sliding in new weatherstrip. If the rough opening has settled, we’re resetting the frame, re-shimming, and re-insulating the gap before we set a new threshold. What drives the addition and ADU range is foundation type, permitting, and finish level. A slab-on-grade ADU with basic finishes runs the low end. A perimeter foundation with a tiled bath and full kitchen runs the high end.
Every scope gets a written line-item price before we unpack a single tool. No change orders that weren’t discussed on site and priced in writing first. And the work carries our 365-Day Done Right Promise: if it’s not right within a year of completion, we make it right at no cost.
DIY or Call Us?
There’s a small set of things you can safely do yourself on a Therma-Tru door. Clean the weatherstrip channel with a damp cloth and check the sweep for brittleness by running a finger along the bottom edge. If it flakes or feels stiff as plastic, it’s done. You can also snug the hinge screws with a #2 Phillips, but if the screws spin without biting, stop there. The jack stud is compromised and you’ll only strip the hole further.
What you should not attempt: pulling a Therma-Tru pre-hung slab out of its frame to reset hinges. A Classic-Craft slab weighs 90 to 120 pounds depending on glass package. It drops wrong, you’re looking at a broken foot, a shattered tile entry, or a snapped hinge jamb. The multi-point lock assemblies also contain high-tension springs, and disassembling one without knowing the release sequence can send a striker plate across the room. We’ve seen the aftermath of weekend attempts. It costs more to fix than it would have to do it right the first time.
If the door is dragging, leaking, or just not closing like it used to, call (213) 632-5711. We’ll tell you what’s likely wrong over the phone and give you a straight price before you commit to anything.
FAQs
A properly installed Therma-Tru door slab will last 20 to 30 years in Los Angeles, but the wear parts (weatherstrip, sweep, sill cap) typically need replacement every 5 to 8 years due to UV exposure and daily use. South-facing and west-facing entries tend to eat seals faster, so if your door gets direct afternoon sun, budget for a sweep swap every 4 to 5 years. Call (213) 632-5711 and we’ll match the right seal to your sill profile for a fixed price.
Seals, sweeps, thresholds, and most hinge issues are repairable without replacing the door slab. Frame failure from settlement is also repairable if we catch it before the jamb splits. The slab itself almost never needs replacement unless it’s cracked, delaminated, or severely warped. For an honest assessment, call (213) 632-5711 and we’ll tell you which side of the line you’re on.
Weatherstrip and sweep replacement takes under an hour on site. Threshold replacement takes 2 to 3 hours including removal, prep, and setting the new cap. A full door system replacement inside an existing frame runs 4 to 6 hours. Most jobs are one visit. Call (213) 632-5711 for a written price before we schedule anything.
We stock common sweeps, hinges, thresholds, and weatherstrip profiles on our trucks for immediate service across Los Angeles. Rare parts, like Classic-Craft multi-point lock assemblies, may take 3 to 5 business days if we don’t have the exact configuration on hand. We’ll never charge you for a part until we’ve confirmed it’s the right one for your door. Call (213) 632-5711 and tell us what your door is doing, we’ll tell you what’s in stock.
Know who’s coming, know what it costs, know it’s guaranteed – everything else is just noise.
Written by Isaac Pruett, Owner, Mason Remodeling Co at Mason Remodeling Co Los Angeles, serving Los Angeles and nearby areas.
