Aluminum Capping for Philadelphia Rowhomes
Wood window frames, sills and trim on an older rowhouse need painting every few years or they rot. Aluminum capping wraps sound wood in custom-bent metal, so the trim keeps its shape without the paint cycle.
Aluminum capping covers exterior wood trim, most often window and door frames, sills, bay windows and porch trim, with aluminum coil bent on site to fit each piece. Done right, the wood is repaired first, the metal is fitted tight with sealed joints and weep paths, and water cannot get behind it. It ends the painting cycle on rowhome trim.
When Capping Makes Sense
Capping works on wood that is still sound. The metal protects the wood from sun and rain; it does not fix rot. So the first step is always probing the frames and sills, cutting out soft wood and replacing it, then priming bare spots before the aluminum goes on.
The quality of a capping job is in the bending and the joints. Each profile is bent on a brake to fit the trim, laps run so water sheds away from the window, and joints against brick and glass are sealed with a flexible sealant. Badly fitted capping catches water behind it and rots the wood faster than bare paint would.
What Sets the Price of Capping
- Number of openingsEach window and door is capped separately.
- Wood repairsRotted sills and frames replaced first.
- Profile complexityBays and detailed trim take more bends.
- Height and accessUpper-floor windows need ladders or lifts.
- ColorStandard and custom coil colors differ.
Capping is priced per opening and per run of trim once the wood has been probed, since rot repairs change the job.
Cap, Paint or Replace?
The right answer depends on the wood and on how the house should look.
| Option | When it fits | Tradeoff |
|---|---|---|
| Aluminum capping | Sound wood, plain profiles, low upkeep wanted | No painting; changes the look slightly |
| Repair and paint | Decorative or historic trim | Keeps detail; repaint every few years |
| Replace the wood | Rot too deep to repair | New trim, then cap or paint it |
Window and Door Frame Capping
Window frames and sills take the most water on a rowhome front, especially the sill, where rain sits and paint fails first. We repair the frame and sill, then cap the brickmold, jambs and sill in separate bent pieces lapped so water runs out and away. The joint to the brick is sealed, and the joint to the window itself is left with a path for water to drain rather than sealed shut. Door frames and transoms are done the same way.
Bay Window and Porch Trim Capping
Bay windows and front porches carry a lot of exposed trim: corner boards, panels, fascia, beams and railing caps. Streetcar-era rowhouses with front porches and second-floor bays have a great deal of this trim, much of it facing the street and the weather. We repair the wood, then cap each surface in aluminum bent to its profile, keeping the lines of the bay or porch rather than boxing them in. Where decorative trim would lose its detail under metal, we recommend repair and paint instead.
Rear Addition Trim Capping
Rear kitchen additions on older rowhouses were often wood-framed with wood trim, and they sit under the runoff from the roofs above. Their window trim, corner boards and fascia are often the first wood on the house to rot. Capping them is often paired with new gutters or a new roof on the addition, so the roof edge, trim and water path are all renewed at once. Where the gutter hangs on the fascia, the fascia is repaired and capped before the gutter goes back up.
Window frames peeling again?
Call and we check the wood and cap it.
What We See on Philadelphia Roofs
The City's Philadelphia Rowhouse Manual points out that rowhouse kitchen and bath additions were often built of wood with wood siding, and that every wood surface needs regular maintenance and painting, which is the work capping replaces. The same guide shows a South Philadelphia cornice covered in vertical aluminum, a reminder to cap trim to its profile rather than boxing in historic detail.
How a Capping Job Runs
- 1
Probe the wood
Frames, sills and trim checked for rot.
- 2
Repair the wood
Soft wood cut out and replaced, bare spots primed.
- 3
Measure and bend
Coil bent on site to each profile.
- 4
Fit and fasten
Pieces lapped to shed water, fastened neatly.
- 5
Seal the joints
Brick joints sealed, drainage paths kept open.
- 6
Clean up
Offcuts and old caulk removed.
Aluminum Capping Questions
No. Rot is repaired first, or it keeps spreading under the metal.
Slightly. Fitted to the profile and in a matching color, it stays close to painted trim.
Mainly resealing joints every several years.
On properties on the Philadelphia Register, exterior changes need Historical Commission approval.
Yes. New windows are often capped at installation.
More Masonry & Rowhome Details Work in Philadelphia
From our guides: Why Porch Roofs Leak on Philadelphia Rowhomes
End the Paint Cycle on Your Trim
Call and we repair the wood and cap it to fit.