Aluminum Window Capping — Wrap Exterior Window Trim in Coil Stock
The wood trim around the windows needs scraping and paint every few years and the bottom corners are starting to go. Capping it in aluminum coil ends the painting, as long as the wood under it is sound first.
Aluminum window capping means bending aluminum trim coil on a brake to cover the exterior wood casing and sill of a window so it never needs paint again. JMB Builders does it across the Twin Cities metro: we probe the wood, replace anything soft, add a drip cap over the head, bend and fit the coil to each leg and the sill, and seal the seams with color-matched caulk. Priced per window, quoted from your photos within one business day.
- Priced per window; cheaper per window in a batch
- Rot found and repaired before it is covered
- Drip cap over the head casing on every window
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
Aluminum window capping is what most 1990s and newer houses in the metro already have: the wood casing and sill nosing around each window are covered with aluminum trim coil, bent on site to the profile of the trim, in a color that matches the siding or the trim. Capping an older house with painted wood casing is the way to stop repainting the trim that takes the most weather on the house.
The catch is the same as any wrap. Coil covers wood; it does not fix it. A casing leg that is soft at the bottom corner stays soft under the aluminum, and the rot keeps going where nobody can see it. We probe every leg and every sill nosing before anything gets bent, cut out what is rotted and splice in PVC or primed wood, and only then cap. A cap over rot is the job we get called to redo two years later.
The parts that make a cap last are small. A drip cap over the head casing, tucked behind the siding, so water never runs down behind the wrap. The sill piece bent with a hem at the front edge so it drips clear. The leg pieces lapped over the sill, not under it. Seams caulked with a color-matched sealant, and the joint between the cap and the window frame sealed so wind-driven rain stays out. Skip any one of those and the wrap channels water instead of shedding it.
What you supply
- Photos: the whole window from the yard, a close-up of each bottom corner of the casing, and one of the sill
- How many windows you want done; the second and third on the same wall are cheaper than the first
- Color: match the siding, the existing trim or the window frames; we bring the coil color chart if you are not sure
- Whether the window frame itself is wood and you want its exposed edge capped too
What JMB supplies
- Rot check with a screwdriver at every leg and sill before the coil goes on
- Rot repair in PVC or primed wood where a casing leg or sill nosing is soft, quoted as its own item
- Aluminum trim coil bent on our brake to the casing profile, one piece per leg, head and sill
- Metal drip cap over the head casing, slipped behind the siding
- Color-matched sealant at the seams, the window frame and the siding
- Stainless or painted trim nails set where the next piece covers them
- Photos of each finished window in your job folder
How it is priced: per window
Quoted in writing from your photos within one business day. What moves the number:
- Number of windows done in the same trip; the brake setup is the same for one or ten
- Casing width and whether the sill nosing and a wood frame edge are capped too
- Rot repair at the bottom corners or the sill before the wrap
- Second-story windows that need staging or a taller ladder
- Wrapping over stucco or brick returns vs. lap siding
- Matching an unusual trim color vs. a stock coil color
Push a screwdriver into each bottom corner of the casing and tell us what you find. Sound wood is a straight cap; soft wood means a corner repair goes on the quote first.
How long it takes
Four to six ground-floor windows with sound trim: one day. Add time for each rotted corner repair and for second-story staging.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Cap over sound wood casing
The casing is solid and just tired of paint. We scrape the loose paint, bend coil to the casing profile, cap the legs, head and sill, add the drip cap and seal the seams. No wood is replaced.
Corner repair, then cap
The bottom of one or both casing legs is soft. We cut the rot out, splice in PVC, check the flashing behind it, and cap the whole leg. The splice disappears under the coil and the water problem that caused it is fixed, not hidden.
Wood window frame edge capped too
On older wood windows the exposed edge of the frame and the sill take weather. We cap that edge and the sill in the same color, leaving the sash alone so the window still opens and closes and can be replaced later.
Whole house, one color
Every window, the door casings and the corner boards capped on one trip so the house reads as one trim color. The brake stays set up and the per-window price drops.
Aluminum Window Capping — Wrap Exterior Window Trim in Coil Stock: questions, answered
What is aluminum window capping?
Capping is covering the exterior wood trim of a window with aluminum trim coil bent to the trim's shape. The coil comes in rolls with a baked-on color, and it is bent on a siding brake on site to fit each leg, the head and the sill. Once it is on, the trim does not need paint and it sheds water instead of soaking it up.
Can you cap window trim that is already rotted?
Not without fixing it first. Rot under a wrap keeps spreading and stays hidden until the window itself goes soft. We cut the rotted section out, usually a bottom corner or a sill nosing, splice in PVC or primed wood, fix the flashing behind it, and then cap. The repair is its own line on the quote so you can see what the coil is going over.
Does aluminum wrapped window trim trap water?
It does when it is done wrong, and that is most of the failed wraps we see. Water gets in when there is no drip cap over the head, when the sill piece is bent without a hem, or when the leg pieces run under the sill instead of over it. Done right, with a drip cap tucked behind the siding and the seams lapped so water runs out, a cap keeps the wood drier than paint ever did.
What colors does aluminum window wrap come in?
Trim coil comes in a long list of stock colors: whites, almonds, clays, browns, grays and blacks, plus most common siding colors. We match it to your siding, your existing trim or the window frames. If the house has an unusual trim color the closest stock coil is usually within a shade, and we can hold a sample against the wall before you decide.
Can you wrap the window frame as well as the trim?
On a wood window we can cap the exposed edge of the frame and the sill along with the casing, which is where most of the paint failure is. We do not cap the sash, because it has to move and it will be replaced someday. On a vinyl or clad window only the wood casing around it gets capped; the frame already has its own finish.
Is it cheaper to cap window trim or replace it with PVC?
Capping is usually less per window when the wood is sound, because nothing comes off the house. PVC trim replacement costs more up front but gives you a new profile and a paintable surface. If most of the casing is rotted, replacing it in PVC makes more sense than repairing it and then covering it. We price both from your photos if you want to compare.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and for the builders and dealers we sub for. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 26, 2026 · JMB Builders LLC, MN license BC809005 · All exterior trim pages
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Exterior trim near you
Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: