Wall Trim · Metal building trim guide
Metal Door Jamb Trim for Roll-Up and Walk Door Openings
Jamb trim covers the sides of door openings, wrapping the framing and the cut panel edges for a clean, sealed finish.
Also called: door jamb trim, door jamb flashing, jamb flashing, roll-up door jamb trim, side trim
Metal door jamb trim finishes the sides of every door opening in a metal building. When you cut a roll-up or walk door opening into a wall, the panel edges and the framing are left raw. Jamb trim wraps that edge so it's sealed, straight and safe to walk past.
It's the piece that makes a door look factory-built instead of cut in with a grinder. This guide covers what jamb trim does, how to measure it with a worked example, and how it laps with the head trim so water stays out.
What is metal door jamb trim?
Jamb trim is sheet metal bent to wrap the side of an opening. One part lies on the outside face of the wall and covers the cut panel edge. The other part returns into the opening and covers the face of the jamb framing.
It does four jobs. It blocks wind-driven rain at the panel edge. It closes the open ribs so wasps and rodents can't nest. It covers sharp cut edges where people and equipment pass. And it gives the opening a finished look. It's also called jamb flashing or door side trim.
Where jamb trim goes on a metal building
Each opening needs solid framing: a jamb post on each side and a header tube across the top. The jamb trim fastens to that framing. Many pre-hung steel walk doors come with their own frame that covers part of the edge, so check what your door includes before you order.
- Both sides of every roll-up door opening.
- Both sides of walk doors, where the door frame doesn't already cover the panel edge.
- Framed openings and frame-outs for future doors.
- Windows, on some buildings. Many builders use J-trim on windows instead.
Jamb trim sizes, gauge, profile and colors
Most jamb trim is 26 gauge steel to match R-panel and PBR walls. 29 gauge versions exist for lighter systems. The return leg must match your jamb framing size, and that varies by building. A 2.5 in. square-tube jamb needs a different bend than a deeper red-iron jamb, so tell us what you have.
It comes in Galvalume or painted colors, usually matching the head and corner trim. Pieces are typically 10 ft long, and longer lengths are often available, so ask us. Custom bends are common for jamb trim because framing sizes vary so much.
How to measure jamb trim and how many pieces to order
Formula: opening height x 2 sides x number of doors = total feet. Add 10% and round UP to whole pieces. Then check it piece by piece: each jamb should be ONE piece from slab to header, with no joint.
Worked example: a 30 x 40 gable building with 12 ft walls and a 3:12 pitch, with one 10 x 10 ft roll-up door and one 3 x 7 ft walk door. Roll-up: 2 x 10 = 20 ft. Walk door: 2 x 7 = 14 ft. Total = 34 ft. Add 10%: 34 x 1.10 = 37.4 ft. With 10 ft pieces, 37.4 / 10 = 3.7, so order 4 pieces.
Piece check: the walk door jambs are 7 ft each, cut from two 10 ft pieces. The roll-up jambs are a full 10 ft each, which leaves no room for error. Order those two as 12 ft pieces (or a custom length) and cut to fit. Final order: two 12 ft and two 10 ft pieces.
How to install jamb trim
- Frame the opening square and plumb, with the header tube across the top.
- Hang the wall panels and cut them back to the jamb framing.
- Cut the jamb trim to run from the slab (or base trim) up to the bottom of the header, tight to the head trim position.
- Set the trim over the panel edge and wrap it around the jamb framing. Check it for plumb.
- Fasten with color-matched #12 tek screws into the jamb framing and #14 x 7/8 in. lap screws through the face into the panel, about 12 in. apart.
- On roll-up doors, install the jamb trim before the door guides go on, if your door installer allows it, so the guides bolt over the trim.
- Install the head trim last so its folded ends lap OVER the tops of both jambs. Seal the joint with butyl tape. Brush off all shavings.
Common jamb trim mistakes to avoid
- Splicing a jamb with a joint halfway up. Use one piece per side.
- Ordering 10 ft pieces for a 10 ft door and coming up short.
- Ordering a return leg that doesn't fit the jamb framing size.
- Putting the head trim on before the jambs, so the jambs end up lapped over the head and leak.
- Forgetting the frame-outs for future doors.
- Leaving cut panel edges exposed inside the opening where they can cut someone.
What to order with jamb trim
- Head trim (drip cap) for the top of each opening
- J-trim for windows and other cut edges
- Base trim, which stops at each jamb
- Inside foam closures for the wall panels
- Color-matched tek screws and lap screws
- Butyl tape or sealant and touch-up paint
Get metal door jamb trim in Houston from Ironrod Steel
Ironrod Steel rolls its own R-panel and PBR and supplies matching metal door jamb trim, head trim, J-trim, closures, screws and butyl tape. Tell us your door sizes and framing size, or send a few photos, and we'll help you build your full trim list. Pick up at 8122 Hillsboro St, Houston, TX 77029, or ask about delivery across Houston and Southeast Texas. Call or text (281) 902-7619.
Jamb Trim FAQ
What is jamb trim on a metal building?
Jamb trim covers the sides of a door opening. It wraps the cut panel edge and the jamb framing so the opening is sealed and finished. It's also called jamb flashing.
How much jamb trim do I need for a roll-up door?
Two pieces, one for each side, each as long as the door is tall. A 10 ft tall door needs two jambs of about 10 ft, so many people order 12 ft pieces and cut them to fit.
Does jamb trim or head trim go on first?
Jamb trim goes first. Head trim goes on last so its ends lap over the tops of the jambs. That way water runs over the joint, not into it.
Do walk doors need jamb trim?
It depends on the door. Many pre-hung steel walk doors for metal buildings have a frame that covers the panel edge. If yours doesn't, you need jamb trim or J-trim on both sides.