Window frame finishing is the collective term for all the linings, boards and mouldings around a window or door frame: everything that closes the junction between the frame and the surrounding structure neatly, and keeps wind and driving rain out. The frame carries and holds the sash or leaf; the finishing completes the job.
What it covers
- Reveal linings — the boarding of the reveal, the side face of the wall opening, between frame and inner wall.
- Stop bead or rebate strip — the strip the opening leaf closes against, which also covers the gap between frame and masonry.
- Head and cill boards — closing off the top or bottom of the opening, for instance at a spandrel panel or under a threshold.
- Window board and external cill — the board inside on the bottom member, the cill or weatherboard outside.
- Beads and mouldings — decorative or sealing strips along the junctions.
- Render stop profiles — plastic or aluminium profiles that take up the joint between render or plaster and the frame.
Why the junction matters technically
The joint between frame and wall moves: timber responds to moisture content, masonry and concrete expand and shrink. Finishing that cannot take up that movement cracks or opens up. Hence the fixed rules:
- Never simply fill it. The gap is made airtight with a compression tape or a sealing membrane, insulated, and only then covered. Expanding foam on its own is neither an air seal nor a rain barrier.
- Seal outside with a flexible sealant in a properly sized joint. Rule of thumb: make the sealant joint about twice as wide as it is deep, and let the sealant bond to two faces only, not to the back of the joint.
- Fall and a drip. Every horizontal external element (cill, flashing) gets a fall away from the building and a nose with a drip groove, so water does not run back along the facade.
- Do not fix it tight. Mouldings forced hard between two fixed elements will twist as soon as the timber or the structure moves.
Related terms
- Window frame
- Frame anchor
- Frame infill panel
- Door and window trim
- Bead
- Movement joint
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