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Cutting MDF Skirting Board: How to Get Tight Internal and External Corners
The neatest way of cutting MDF skirting board is with a mitre saw and a fine carbide-tipped blade with plenty of teeth. For a standard 90-degree corner, you cut both lengths at a 45-degree mitre. If the corner is out of square, measure the angle and set the saw to half of it.
This guide covers internal and external corners, walls that are not square, long runs and how to finish the joints so they stay tight.
What will you learn in this article?
- Which saw should you use for MDF skirting board?
- Which saw blade should you use for MDF skirting?
- How do you measure skirting board?
- Should the skirting stand upright or lie flat on the mitre saw?
- How do you cut an internal corner?
- How do you cut an external corner?
- What if the corner is not 90 degrees?
- How do you join skirting on a long wall?
- How do you avoid damaging pre-finished skirting?
- How do you finish joints and corners?
- Cutting safely with a mitre saw
- Frequently asked questions about cutting MDF skirting board
- In short: cutting MDF skirting board
Which saw should you use for MDF skirting board?
A mitre saw is the most practical choice. You set the angle on the scale, the board sits firmly against the fence and every cut is square and repeatable. A cordless sliding mitre saw from the Maxxpack 18V range can go from room to room without a cable.
If you only have a few lengths to cut, a fine-toothed handsaw in a mitre box will do. It takes more effort and the cut is less crisp, but for a downstairs toilet or a small room it works. A jigsaw is not suitable for the mitres themselves, but it is useful for coping the profile on an internal corner (see below).
Skirting cutters or trim shears are designed for thin laminate or plastic skirting. They are usually not suitable for MDF.
Which saw blade should you use for MDF skirting?
Use a fine carbide-tipped (TCT) blade with a high tooth count. A blade with few teeth chips the finish on primed or pre-finished skirting and leaves a fluffy edge. For a typical mitre saw blade, 60 to 80 teeth is a common choice. Check the specifications of your saw for the correct blade diameter and bore size. Keep the blade clean, because glue and paint residue make the cut rougher.
How do you measure skirting board?
Measure each wall along the floor, not halfway up. For each wall, note whether the ends will be an internal corner, an external corner or a straight end (at a door frame).
- Internal corner: the wall measurement is the long side of the board, at the back (against the wall).
- External corner: the wall measurement is the short side at the back. The front face ends up longer.
When buying, allow roughly 5 to 10 per cent extra for offcuts, out-of-square corners and the odd mistake. If you have lots of short pieces and corners, you will need more.
Should the skirting stand upright or lie flat on the mitre saw?
The easiest method is to stand the board upright, with the back against the fence and the bottom edge on the saw table, just as it will sit against the wall. You then only need to set the mitre angle (turning the saw left or right). If a tall skirting board does not fit under the blade, lay it flat and cut using the bevel setting instead. That takes more thought about which way to cut, so make a test piece first.
How do you cut an internal corner?
- Stand the board upright against the fence, with the face towards you.
- Set the saw to 45 degrees.
- For the left-hand board of the corner, cut so the back is longer than the front; for the right-hand board, mirror the angle.
- Hold both pieces loosely in the corner and check the fit before you fix them.
With profiled skirting, you can also scribe (cope) an internal corner. Cut one board square so it butts into the wall. Cut the other board at a mitre first, then use a jigsaw or coping saw to cut away along the profile line the mitre reveals. That board then fits exactly over the profile of the first. A coped corner stays closed better if the wall moves slightly.
How do you cut an external corner?
On an external corner, the front of the board is longer than the back. Cut both boards at 45 degrees, but in the opposite direction to an internal corner. Cut them slightly too long first, hold both pieces against the corner and trim in small steps until the points meet exactly. A little wood glue or grab adhesive in the mitre holds the corner together.
What if the corner is not 90 degrees?
In practice, walls are rarely perfectly square. Measure the angle with an angle finder or sliding bevel and divide it by two. If the corner is 92 degrees, for example, cut each board at 46 degrees. If you find measuring difficult, place two test offcuts in the corner and adjust them until they close; you can then read off the right setting. For internal corners, the coping method above also hides small deviations.
How do you join skirting on a long wall?
If the wall is longer than one board, do not butt the pieces square together. Use a scarf joint instead: cut both ends at 45 degrees so they overlap. An angled joint is less visible and stays closed better if the material shrinks a little. Keep the joint away from a corner and, ideally, place it behind a cupboard or door.
How do you avoid damaging pre-finished skirting?
- Cut with the face positioned so the teeth enter it first: on a mitre saw, that is the side facing up or towards you.
- Put masking tape over the cutting line.
- Let the blade stop completely before lifting it out of the cut.
- Lay the boards on a clean surface so the finish does not get scratched.
How do you finish joints and corners?
Fill small gaps in corners and joints with decorators' caulk or filler, smooth it with a damp finger or filling knife and let it dry. Sand lightly and touch up with paint in the colour of the skirting. Fill nail holes the same way. Run paintable acrylic caulk along the joint between the skirting and the wall.
Cutting safely with a mitre saw
Keep your hands well clear of the cutting area, clamp short pieces rather than holding them, and connect a vacuum to the dust port if you can.
Frequently asked questions about cutting MDF skirting board
Can I cut MDF skirting without a mitre saw?
Yes, with a fine handsaw and a mitre box. It takes longer and the cut is less crisp, so expect to do a bit more filling in the corners.
Why do my mitres not close?
Usually the corner is not exactly 90 degrees, or the board was not flat against the fence when you cut it. Measure the angle, divide it by two and hold the board firmly against the fence.
Should I cut first or paint first?
Cut pre-finished skirting as it comes and touch up the joints afterwards. With unfinished MDF skirting, it is best to prime and paint it first, then fill and touch up the joints and nail holes once it is fitted.
Which side of the skirting goes against the fence?
When cutting upright, the back of the board (the side that goes against the wall) sits against the fence and the bottom edge rests on the saw table. That way you cut the board in the same position it will be fitted.
In short: cutting MDF skirting board
Use a mitre saw with a fine TCT blade, stand the board upright against the fence and cut standard corners at 45 degrees. Measure out-of-square corners and halve the angle, cut external corners slightly long first and join long runs with a scarf joint. Finish small gaps with caulk and paint.