What is a window frame?
A window frame is a wooden, plastic, or aluminium framework placed in a wall to contain a window or door. The frame forms the fixed surround in which the opening part (the window sash or door) is hung. It is the connection between the wall and the glazing.
Components of a window frame
A window frame consists of four main components:
| Component | Position | Function |
|---|---|---|
| Head | Top | Horizontal member at the top, rests on the lintel |
| Sill | Bottom | Horizontal member at the bottom, drains water away |
| Jambs | Left and right | Vertical members on either side |
| Rebate | Inner edge | The step in which the window sash or door sits |
On a window frame, there is often also a drip edge (weatherbar) on the sill: an angled edge that directs rainwater away from the frame.
Types of window frames
Wooden frame
The traditional choice. Easy to work with, paint, and repair. Requires maintenance (painting every 5-7 years). Widely used in renovation and self-build projects.
Plastic frame (uPVC)
Maintenance-free with good insulation. Cannot be painted a different colour (unless specially treated). Popular in new-build construction.
Aluminium frame
Slim profile, strong, and maintenance-free. More expensive than wood or plastic. Often used in modern architecture.
Installing a frame in a garage or renovation
When building a garage or renovating an existing building, the window frame is an important component:
- Measure the reveal — The opening in the wall where the frame goes. Always measure at several points (top, middle, bottom).
- Check the rebate size — The rebate size is the dimension of the glass or panel that fits in the frame.
- Place the frame in the reveal — The frame is set in the opening, aligned level and plumb.
- Secure — With frame screws or plugs into the masonry.
- Finish — The gap between frame and wall is sealed with sealant and finished with a trim strip.
Adjustment space
Between the frame and the wall, there should be 5-10 mm of adjustment space. This gives you room to level the frame and is later filled with PU foam and sealed.
Dimensions and terminology
- Reveal size — The dimension of the opening in the wall (from reveal to reveal)
- Frame size — The outer dimension of the frame (slightly smaller than the reveal size)
- Rebate size — The dimension of the glass that fits in the rebate
- Adjustment space — The space between frame and wall for alignment
Common mistakes
- Not installing level — A crooked frame causes windows and doors not to close properly
- Too little adjustment space — Without adjustment space, you cannot align the frame
- Sill not draining — If the sill is flat, water stands and the wood rots
- No drip edge on the outside — Water then runs down the facade instead of dripping off
Related terms
- Lintel
- Reveal size
- Rebate size
- Glazing
- Drip edge