Therma-Tru Home Additions & ADU Nationwide

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

If you’re planning a home addition or ADU in Pasadena and you want Therma-Tru entry doors, windows, or patio doors in the build, you’re looking at a total project cost of $45,000 to $130,000 depending on square footage, foundation work, and finish level. We install Therma-Tru products as part of larger addition and ADU projects throughout Pasadena, and we carry the common hardware, thresholds, and weatherstripping on our trucks so a door or window issue doesn’t stall your project. Most people reach out to us because their existing Therma-Tru door on an older home near Bungalow Heaven or Madison Heights has started binding, or the weatherseal on a patio door has gone flat from years of San Gabriel Valley sun. Once a Therma-Tru product fails, the door no longer seals, the frame lets air through, and you start seeing daylight where you shouldn’t.

Call (626) 657-5396

Which Therma-Tru Models This Applies To

Therma-Tru makes two main door families that show up in Pasadena additions and ADUs: the Classic-Craft line (fiberglass with a wood-grain finish, sold through dealers and lumberyards) and the Pulse line (polyurethane core, lighter weight, often shaped around the price point). Within those families, the door slab thickness runs 1-3/4 inches on most residential models, and the hinge prep is standard 4-1/2-inch spacing, so hardware is interchangeable across the brand. The compatibility gotcha is the threshold: Therma-Tru uses a proprietary composite adjustable threshold on Classic-Craft models, and a generic aluminum threshold from a big-box store won’t sit right in the sill channel. We stock the Therma-Tru-form factor on the truck, along with OEM and quality aftermarket weatherstripping that matches the brand’s compression profile. For an ADU, the door is often ordered with a pre-finished fiberglass frame, which means touch-ups after installation are rare, but the frame has to be ordered in the correct rough opening size from the start. If the door was installed before 2010, you likely have the original Classic-Craft with the older threshold design, and replacement sills for that generation are harder to source as Therma-Tru quietly phased out old tooling.

Signs Your Therma-Tru Home Additions & ADU Is Failing

• Daylight visibly visible at the bottom corners of the door. This means the threshold has settled or the weatherstripping has compressed past its useful life. On older Pasadena additions, the slab may have shifted, but more often the rubber has simply gone hard from sun exposure.
• The door no longer latches without lifting the handle or shoving it with a shoulder. Hinges wear, and the door hangs slightly out of square. The strike plate needs adjustment, or the frame has moved. Left alone, it gets worse through summer as the heat causes the fiberglass to expand and bind harder.
• A soft, spongy feel in the bottom rail when you press on it. Fiberglass skins don’t rot, but the wood stiles and rails inside an older Therma-Tru door can accept moisture through screw holes or a failed seal at the threshold. The frame may still look fine from outside, but the core is going.
• Condensation or fog between the glass panes in a Therma-Tru patio door sidelight or the newer glass-insert entry doors. The insulated glass unit seal has failed. Once the argon or krypton fill escapes, you lose the thermal break, and your ADU’s cooling cost creeps up.
• The door makes a hollow clack instead of a solid thud when it closes. Weatherstripping has gone stiff and flat. The door doesn’t compress against the seal anymore, and every close lets conditioned air out through the gaps. This is the most common invisible failure we see, because people just live with it for years.

Replacement Cost & What’s Included

A full Therma-Tru-spec addition or ADU project in Pasadena runs $45,000 to $130,000 for the whole build. Therma-Tru doors and windows are a small but real line item inside that: a replacement entry door slab typically lands between $2,500 and $6,500 installed, while a patio door replacement runs $3,000 to $8,500 depending on glass pack, sizing, and frame condition. The range is driven by whether we’re doing a slab-only swap into an existing frame that’s still square, or a full frame-out because the rough opening has water damage or the old sill was never flashed correctly against a stucco wall. Every quote includes the part, labor, old-material haul-off, and a written price before any work starts. The work itself carries our 365-Day Done Right Promise: if the install isn’t right, we make it right, in writing, no argument. We also pull permits and pass inspections when the job requires it, which matters if your ADU needs a final sign-off from the city’s building department before you can legally rent it out.

DIY or Call Us?

There’s a safe middle ground for a Therma-Tru door. You can check the hinges for looseness, clean the threshold channel of debris, and inspect the weatherstripping for flat spots all without touching a tool. If the door is simply dragging at the bottom, adjusting the threshold height is a homeowner-level task on the composite adjustable models: there are two adjustment screws under the threshold caps. What you shouldn’t try yourself is pulling a full pre-hung unit out of a load-bearing wall in an addition, because the framing around a Pasadena stucco opening is doing structural work, and once you cut the flashing, you own any water intrusion that follows. Same story for a failed insulated glass unit: the glass pack is under compression and the retaining system on Therma-Tru’s newer models is not forgiving. We’ve walked too many homeowners through a DIY removal that ended with a cracked sash. Call (626) 657-5396 and we’ll tell you over the phone whether it’s a threshold adjustment you can handle or a job for a crew that carries Therma-Tru parts on the truck.