Therma-Tru Home Additions & ADU Nationwide

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

Rowan Construction Group Pomona stocks and installs Therma-Tru entry systems for home additions and ADU projects, with typical installed pricing from $45,000 to $130,000 for full additions and $90,000 to $220,000 for detached ADUs in the Pomona market. We carry Therma-Tru Classic-Craft, Smooth-Star, and Fiber-Classic series doors in common slab sizes from 2’8″ to 3’0″ widths, and we can typically source less common dimensions within two business days. Most Pomona homeowners discover their Therma-Tru unit needs attention during the ADU planning phase, when they realize the stock door on their converted garage or new build won’t meet the energy code or aesthetic match the main residence.

Call (626) 606-1081

Which Therma-Tru Models This Applies To

We regularly specify three Therma-Tru lines for Pomona additions and ADUs. Classic-Craft carries a wood-grain fiberglass skin with a polyurethane core, rated for high thermal performance, and it’s the line we use most often when the main house already has a premium entry door that needs matching. Smooth-Star is the paintable fiberglass option, field-proven in Pomona’s inland heat, where dark colors on south-facing ADUs can cause lesser doors to warp. Fiber-Classic is the economy fiberglass line, still thermally broken, and it’s what we quote when the budget is tight but the code still demands an Energy Star-rated assembly.

To identify your existing Therma-Tru unit, check the hinge edge of the door slab for a stamped manufacturing date and series code. The label is usually under the finish coat on fiberglass doors, so you may need to look closely at the hinge mortise area. If you’re matching an existing door in a Pomona home built between 2010 and 2020, it’s likely a Smooth-Star or early Fiber-Classic with a 1-3/4″ thickness. We source OEM Therma-Tru components through authorized distribution, though for some ADU applications we’ll spec a compatible assembly from our vetted alternatives when the lead time on OEM exceeds the permit timeline.

Signs Your Therma-Tru Home Additions & ADU Is Failing

• Visible delamination at the stile or rail joints. The fiberglass skin separates from the internal frame, usually starting at the lock block or bottom rail. In Pomona, this accelerates when afternoon sun hits a dark-colored door on a west-facing ADU, because the thermal expansion coefficient of fiberglass differs from the wood-composite core.
• Air leakage around the perimeter weatherstrip. You feel a draft at the threshold or jamb even with the door latched. The cause is often compression set in the bulb seal, which loses memory faster in dry inland climates like Pomona’s, or frame racking from an unlevel ADU subfloor that settled after the original install.
• Difficulty latching or a sagging hinge side. The door binds at the top corner or requires lift to engage the deadbolt. On Therma-Tru units, this typically traces to hinge screw withdrawal from the composite stile, especially when the original installer used standard rather than long-thread screws into the structural framing.
• Condensation between the door and storm door. Trapped moisture promotes finish failure on the fiberglass skin and can migrate to the jamb. Pomona’s cool winter mornings followed by rapid warming create this microclimate on enclosed ADU entries more than on ventilated porches.
• Finish chalking or color shift. The gel coat surface degrades to a powdery residue. UV exposure at Pomona’s elevation, roughly 850 feet, delivers more intense radiation than coastal markets, and dark colors without factory-applied topcoat show it first.

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Replacement Cost & What’s Included

For a Pomona home addition or ADU, a complete Therma-Tru entry system replacement, including prehung door, frame, hardware, and installation, typically falls between $45,000 and $130,000 for the full addition scope, with the door assembly itself representing $2,800 to $6,500 of that total depending on series and sidelite configuration. A standalone Therma-Tru door swap on an existing ADU runs $1,800 to $4,200 installed.

What drives the range: sidelites and transoms add 40-60% to material cost; stucco return work on an existing ADU opening adds labor; and if the original frame is out of square by more than 3/8″, we rebuild the rough opening, which we document with photos before and after. Under Clause 1 of the Haven Standard, the written price covers exactly what we scope. No change proceeds without a signed change order. The 365-Day Done Right Promise applies to all installation work, and the Therma-Tru factory warranty on the slab transfers to you.

DIY or Call Us?

There’s a short list an owner can safely check. Verify the door is actually Therma-Tru by finding the stamp code. Confirm the rough opening width and height, measured at three points each. Check whether the threshold is adjustable, which tells you if the leak is fixable with a turn of a screw.

Where DIY goes wrong: prehung door installation in an ADU or addition requires shimming the frame plumb in three planes while maintaining consistent reveal, then fastening through the jamb into structural framing without distorting the unit. Get it wrong and the door binds, the weatherstrip won’t seal, or the multipoint lock won’t engage. Stucco and trim repair on the exterior side is not forgiving. Measure twice, then we can talk. Call (626) 606-1081 and we’ll scope it, price it in writing, and install it with a photo record you keep.

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