Header sizing, structural sign-off, finished. We turn an existing window opening into a real door — permitted and warrantied.
Cutting an opening lower is the easy part. Sizing the header, getting a stamped letter, and patching the wall so it looks like the door was always there — that's the work.
When a 3-foot kitchen window becomes a 6-foot French door, the load path above that opening changes. CRC R602.7 sets minimum header sizes by span, but a 6-foot opening in a load-bearing wall in LA's seismic zone (CRC R301) usually needs a 4×10 or 4×12 with full king and trimmer studs — not the doubled 2×6 that was probably sitting above your window. We size the header off the actual roof or floor load above, not a generic span chart, and we attach an engineering letter to the permit so the inspector signs off without three rounds of corrections.
LADBS treats this as an alteration permit, not a window swap. That means a stamped engineering letter, a structural plan check, and a footing/header inspection before you close the wall. Skip the permit and the work shows up on a future appraisal or sale — buyers' inspectors flag unpermitted door cuts in exterior walls more often than any other item.
The finish work is what separates a real conversion from a hack. Outside, the stucco patch has to blend three coats deep — scratch, brown, and color — with a texture pass that matches the surrounding wall. Inside, the drywall has to feather past the old window jamb line so you can't read the patch under raking light. Threshold pan flashing under the new door, exterior trim re-flashed into the existing weather barrier, electrical relocated if the old window switch leg is in the way. We quote the finish work — most contractors quote the cut and call the patch "by others."
Includes engineering letter, permit, header lumber, threshold pan, finished door, exterior stucco patch, interior drywall finish.
Cutting a load path is structural liability — if the header is undersized, the wall sags, the door binds, and three winters later there's a horizontal crack across the lintel. Most door installers carry installer-level liability, not structural. They'll happily widen an opening and hope the existing header was overbuilt, but they won't put their name on the load math. So the homeowner ends up either calling a GC (who marks up the door 40%) or chasing an engineer themselves and paying $1,200–$2,000 for a one-off letter.
The permit dance is the second reason. LADBS plan check on an alteration permit takes 4–8 weeks if you submit cold. Most door installers don't have a relationship with the counter, don't know which plan checker handles structural alterations, and don't have a stock engineering letter format that gets approved on the first round.
We solved both. Our structural engineer is on retainer — letters turn around in 5–7 business days, included in the price. We submit through LADBS e-permit with a packet that's been approved a hundred times. Plan check averages 2–3 weeks for us, not 8.
We've been called to fix all six, more than once. Every one is avoidable at install.
Engineering review is its own step — that's what makes the difference between a 3-week permit and an 8-week one.
"We were doing a backyard remodel and wanted the kitchen window over the sink turned into a French door to the new deck. Two contractors said they'd "sub the engineering" and one said no. Red Stag had the letter back in a week and the whole thing was permitted, cut, and finished in 17 days. Stucco patch is invisible."
"ADU conversion — we needed a side window opened up into the entry door for the unit. The plan checker rejected the first round of plans (not Red Stag's fault, the city wanted a different load calc). Theo's engineer turned the revision in two days. Final inspection passed first try."
"Bedroom window to a 6-foot slider opening onto the backyard. Wall was load-bearing. They put in a 4×12 header, rebuilt the studs, and the drywall blend on the inside is genuinely better than the rest of the wall. Quote was $8,400, final was $8,400."
Same crew, same engineer, same 45-minute drive if anything moves in 2031.
A window-to-door conversion — turning an existing window opening into a door opening to a patio, yard, or deck — is one of the most transformative single projects in an LA home remodel. It creates indoor-outdoor flow where it didn't exist, and it's often less expensive than homeowners expect because the rough opening modification is straightforward when it's properly engineered.
The structural scope. Every window-to-door conversion requires a permit and structural review, because widening or heightening a rough opening in an exterior wall requires confirming the existing header can span the new dimension (or replacing it with one that can). In most LA homes, the header above a window opening is already sized for a door-width span because they're framed the same way — but we verify this with an engineer before quoting and include the engineer's letter in the permit package.
The opening modification. We cut the existing stucco and sheathing, sister or replace framing as the structural scope requires, install the new header if needed, re-flash the entire opening from scratch, set the door unit, and patch the exterior stucco. On a conversion from a standard window to a single door, this is typically a 1.5–2 day project. A conversion to a multi-panel patio door runs 2–3 days depending on the header span.
Thresholds and grades. The floor level determines what threshold detail is possible. If the interior floor is significantly above exterior grade, you'll need steps or a ramp on the exterior — we coordinate that scope with a concrete or decking contractor. If a flush threshold (zero-step) is the goal, the grade on both sides needs to be level within about 1/4 inch, which often means exterior concrete work as part of the project.
Interior finish scope. A conversion typically leaves exposed framing on the interior where the wall below the former window was removed. Drywall patching, baseboard extension, and interior trim matching are not always included in a door installer's scope — we're transparent about where our scope ends and where a finish carpenter or painter needs to be involved.
Free consult, no deposit to quote. We tell you at the walkthrough whether the wall is a clean conversion or a steel-beam job — before you commit to anything.
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