Drywall-return windows can be trimmed with real wood jambs and casing at any time. The return is cut back, the gap between the window frame and the framing gets low-expansion foam and a backer-rod-and-sealant air seal, jamb extensions bring the frame flush with the wall, and casing goes around the outside. It is priced per window.
That applies to any newer Twin Cities house, Blaine, Otsego, Lakeville, Woodbury, where the builder turned the drywall into the window and stopped. Below is why builders do it, what the upgrade involves, what is behind the trim and why it has to be sealed, the two casing styles, and what moves the per-window price.
Why do builders use drywall returns?
A drywall return needs corner bead, mud and paint, all trades already on site. Wood jambs and casing need a finish carpenter, more material and a painter coming back. On a 30-window house that is real money and days on the schedule, so production builders default to drywall unless the buyer upgrades.
The downside shows up over the first few winters. Drywall corners at windows get bumped by blinds and cleaning, hairline cracks open at the miters as the house dries out, and condensation on cold Minnesota mornings stains the sill area. Wood trim is more durable, easier to repaint, and makes the window look finished.
How is trim added to a drywall-return window?
Four steps. First, the drywall return is cut back to expose the window frame and the rough opening, usually to the thickness of the jamb extension. Second, the gap between the window frame and the framing is sealed, which is covered in the next section. Third, jamb extensions, 3/4" wood or MDF ripped to the exact depth from the window frame to the drywall face, are installed and shimmed so they land flush with the wall. Fourth, casing is nailed around the outside, with a stool and apron if that style is chosen.
The depth of the jamb extension varies from window to window, even in the same room, because drywall is not perfectly flat and windows are not all set to the same depth. Measuring and ripping each one is where the skill and the time go.
What is behind the trim, and why does it need an air seal?
Every window sits in a rough opening that is bigger than the window, usually by 1/4" to 1/2" on each side. That gap is what lets the installer shim the window plumb and square. It is also a direct path from the wall cavity to the room. Once the trim goes on, nobody sees the gap again for decades, so what goes in it matters more than the casing profile.
There are three ways the gap gets treated in Twin Cities houses. Fiberglass stuffed in with a putty knife, common in older builds and in a lot of drywall-return houses: it slows air but does not stop it, and in a Minnesota winter it collects frost where warm room air meets the cold framing. Low-expansion window-and-door foam: it fills the gap, insulates it, and stops most of the air, as long as it is the low-expansion type, since regular gap filler can bow a vinyl frame and bind the sash. And the belt-and-suspenders version the energy codes and window manufacturers point to: foam in the depth of the gap, then a backer rod pressed into the last 1/4" to 3/8" on the room side and a bead of sealant over it. The sealed joint at the interior is the air barrier. The foam is insulation. You want both.
Drywall returns need exactly the same treatment. Corner bead and joint compound are not an air seal; they crack at the window frame within a season or two, and the hairline crack you see at the edge of a drywall return is usually where the draft is coming from. When the return is cut back for wood trim, that is the one chance to foam and seal the gap properly before the extension covers it.
Jamb extensions have their own joints to seal. A bead of sealant goes where the extension meets the window frame, so air cannot slip between the two, and the joint between the extension and the drywall gets covered by the casing and caulked. On the outside of the house nothing changes: the flashing tape, sill pan and exterior sealant that keep water out were done when the window went in, and interior trim does not touch them. If a window shows water staining at the bottom corners, that is a flashing problem to fix before any trim goes on.
| Method | Insulates | Stops air | Notes |
|---|---|---|---|
| Fiberglass stuffing | Somewhat | No | Collects frost and moisture in winter; common in older Twin Cities homes |
| Low-expansion foam | Yes | Mostly | Must be the window-and-door type so it does not bow the frame |
| Foam plus backer rod and sealant | Yes | Yes | Sealant on the room side is the air barrier; the standard for a trim-out |
Stool-and-apron or picture-frame casing?
Stool-and-apron is the traditional Minnesota look: a horizontal stool (what most people call the sill) that projects past the casing with an apron underneath, and casing up the sides and across the top. It gives you a small shelf, matches older homes, and handles condensation better because water lands on a horizontal wood surface instead of a drywall edge.
Picture-frame casing runs the same profile on all four sides, mitered at the corners. It is cleaner, more modern, and a bit faster to install. It works with black or dark bronze windows and in rooms where you do not want a ledge.
- Stool-and-apron: traditional, a ledge for plants, best for older homes and stained trim.
- Picture-frame: clean and modern, matches many newer builds, slightly less labor.
- Either style can be paint-grade MDF or stain-grade wood.
White paint-grade or stained wood?
For most newer Twin Cities homes, white paint-grade MDF or primed pine casing is the right call. It matches the existing base and door casing, it costs less, and the joints get caulked so the finish is seamless. Stain-grade oak, maple or fir makes sense when the rest of the house has stained trim, or on a feature window where the wood should show. Stain-grade jambs and casing cost more in material and take more care to fit, and the staining is its own line on the quote.
How is window trim priced?
Per window. Published 2026 cost guides put a typical single window with paint-grade jamb extensions and casing in the low hundreds of dollars for labor. Stool-and-apron, larger windows, mulled units and stain-grade work move the number up. Because it is per window, trimming the living room and kitchen this year and the bedrooms next is normal, and the look stays consistent if you use the same profile.
To get a firm number, send three photos: one window straight on, one from the side showing the drywall return depth, and a shot of your existing door casing so the profile can match. you hear back from us within one business day.
What JMB Builders does
JMB Builders is a licensed Minnesota residential building contractor (BC809005) based in Zimmerman, working across the Twin Cities metro. One crew cuts back the returns, foams and seals the gap, rips and sets the jamb extensions, cases the windows and caulks and fills, paint-grade or stain-grade, one room or the whole house. Painting is quoted as a separate line, or leave it primed and paint it yourself. Paid by check or direct deposit. Call 763-250-3621 or send photos through the site.
- Drywall returns vs. wood casing, the upgrade explained — jmbbuildersmn.com/services/window-trim/drywall-returns-vs-wood-casing
- Jamb extensions for windows — jmbbuildersmn.com/services/window-trim/jamb-extensions-for-windows
- Window stool and apron — jmbbuildersmn.com/services/window-trim/window-stool-and-apron
- Picture-frame window casing — jmbbuildersmn.com/services/window-trim/picture-frame-window-casing
- Cracked drywall window returns, repaired — jmbbuildersmn.com/services/window-trim/drywall-window-returns-repair
- Trim and door painting, quoted as its own line — jmbbuildersmn.com/services/painting/trim-and-door-painting
- The finish carpentry hub — jmbbuildersmn.com/services/finish-carpentry
- Send three photos and we reply within one business day.
Frequently asked questions
Can I add trim to drywall-return windows without damaging the walls?
Yes. The drywall return is cut back cleanly and the new jamb extension and casing cover the cut edge. A little touch-up paint along the outside edge of the casing is normal. No drywall patching is needed on a typical window.
What are jamb extensions?
Jamb extensions are boards, usually 3/4" wood or MDF, that run from the window frame out to the face of the drywall so the casing has something flat to land on. Each one is ripped to its own depth because the wall is never perfectly flat. They are the part of the job that takes the most measuring.
Should the gap around a window be foamed or stuffed with insulation?
Foamed, with low-expansion window-and-door foam, then finished on the room side with backer rod and a bead of sealant. Fiberglass stuffing slows air but does not stop it, and it collects frost in a Minnesota winter. The sealant joint at the interior is what actually stops the draft; the foam insulates the gap. Regular high-expansion foam can bow the frame and bind the sash, so it stays off windows.
Do drywall-return windows need an air seal too?
Yes. The corner bead and joint compound on a drywall return are not an air barrier, and the hairline crack that opens where the drywall meets the window frame is usually where the draft comes from. Cutting the return back for wood trim is the chance to foam and seal the gap before the jamb extension covers it. Done that way, the trim-out fixes a draft as well as the look.
How much does it cost to trim a drywall-return window?
Published 2026 cost guides put a single window with paint-grade jamb extensions and casing in the low hundreds of dollars for labor, priced per window. Stool-and-apron, large or mulled windows and stain-grade wood push it up. Painting is quoted as a separate line, or leave the trim primed and paint it yourself.
Does wood trim help with window condensation?
It does not change how the glass performs; that is set by the U-factor on the NFRC label. What it changes is what the condensation lands on, and sealing the gap behind the trim keeps cold air from chilling the frame edge where moisture forms first. A painted wood stool and jamb hold up far better than a drywall edge when moisture shows up on cold mornings, and they are easier to wipe and repaint.
