Doors, Windows, Fittings and Joinery
This section covers door and window frames, shutters, hardware, clearances, glazing, and joinery joints. The exam tests whether you can set a frame plumb and square, size a leaf correctly, fit ironmongery, and avoid sticking or leaking.
Core rules
- Set frames plumb, level, and square; brace them while fixing so they do not twist.
- Allow clearances: typically about 2–3 mm at the sides and top of an internal door leaf, with a slightly larger gap at the floor for clearance and ventilation.
- Fit hinges so that the knuckle projects clear of the frame; check that screws bite into solid timber, not just plaster.
- Use mortise-and-tenon, dowel, or biscuit joints appropriate to the member and loading; glue and clamp correctly.
- Weather seals, drips, and sill slopes keep water out of external windows and doors.
- Treat cut ends and concealed faces before assembly, especially in wet areas.
Worked example
A door opening is 900 mm wide and 2100 mm high. The frame is 70 mm wide on each jamb and the head, with a 3 mm clearance each side and a 3 mm gap at the head. Leaf width = 900 − (2 × 70) − (2 × 3) = 754 mm. Leaf height = 2100 − 70 − 3 = 2027 mm, before any floor clearance. The reasoning: deduct the frame members and the specified clearances from the structural opening, not from the frame’s outside size.
Traps
- Fixing a frame before checking it for plumb and square.
- Leaving no clearance, so the door binds after painting or swelling.
- Fitting hinges with screws that only grip plaster.
- Omitting a drip or sill slope on external joinery.