Introduction
Accurate measuring and cutting is the key to a professional-looking window board installation. This guide covers everything from taking the initial measurements to making the final cuts — including how to handle tricky angled reveals and horn cuts.
Tools You'll Need
- Steel tape measure
- Mitre saw (preferred) or circular saw
- Jigsaw (for horn cuts)
- Pencil and set square
- Sandpaper (120 grit)
Step 1 — Measure the Width
Measure the width of the window recess at the front, middle, and back. Use the smallest measurement to ensure the board fits. Add the overhang you want at the front (typically 20–30mm).
Step 2 — Measure the Depth
Measure from the back wall to the front face of the window reveal. This is your board depth. Standard window board depths are 219mm, 244mm, or 295mm.
Step 3 — Check for Square
Use a set square to check if the window reveal is square. If the reveals are angled, you'll need to cut the ends of the board at a matching angle rather than 90°.
Step 4 — Mark Up the Board
Transfer your measurements onto the board using a pencil and set square. Mark the cut lines clearly.
Step 5 — Cut the Length
Use a mitre saw for a clean, straight cut. Always cut on the waste side of the pencil line.
Step 6 — Cut the Horns
If the board extends past the window reveal, mark and cut the horn notches using a jigsaw. The horn depth should match the thickness of the plaster/render on the wall face.
Step 7 — Sand the Edges
Lightly sand all cut edges with 120 grit sandpaper for a smooth, paint-ready finish.
Pro Tip: Always cut slightly long and test fit before making your final cut — MDF can't be lengthened once cut!