In order to get a tight joint you have to scribe skirting board at internal corners instead of mitering it. This means fitting one board tight into the corner, then cutting the next one to match the exact profile so it fits perfectly up against the first.
Whilst this sounds difficult for very intricate mouldings it is actually really straight forward. This page has everything you need to know first for internal 90° corners, and after that to scribe skirting board into corners other than 90 like 122.5°, often found in bay windows.
Step 1: Cut a back mitre
I Take a measurement for the next piece and add about 100mm. Transfer this measurement to a new piece of skirting board and cut to length. Place this onto the chop saw standing up exactly as it will be on the wall and turn the saw to 45°, as though you were mitering the internal corner.
Cut down through the top part of the moulding only, and stop when the saw blade reaches the flat surface, like in the picture of Chamfered skirting below.
Step 2: Use a compass to scribe skirting board shape
Offer this up to the board that is already nailed in place. Put the pencil in your compass and use it to scribe the shape of the first board onto the second as shown in the picture (start the pencil line from the saw cut downwards). You can now see the exact amount (everything to the right of the pencil line) that needs to be cut out!There is a new tool available that is great for scribing internal corners and also the board down to the floor (amongst loads of other things). The Trend Easy Scribe Tool is an essential tool for any fixing carpenter to have in their toolbox.
Step 3: Cut the waste out
If when you scribe skirting board it's perfectly straight then it can be cut with a miter saw. If not, I use my jigsaw with a downward cutting blade. Keeping the saw blade to the right hand side of the pencil line I carefully cut the skirting up to the part first scribed with the compass. Let the blade stop and remove the jigsaw. Finish the rest off with a coping saw that has a fine blade. When coping intricate baseboard trim, it's sometimes difficult to remove the waste so to make this easier cut at an angle, taking more timber out of the back of the board where it won't be seen. By doing this you ensure it doesn't get in the way of the face edges touching if the wall is very slightly out of square. Finally sand off any pencil lines and,
It should fit like this!
When the corner is not 90°, the method is the same but there's a little more worth knowing in order to scribe skirting boards in tight. Again, as above cut one board tight into the corner, using a bevel to determine the angle and fix it firmly in place. I fix it at this stage otherwise you could scribe into a board that's going to move when you fix it.
Step 1: Bisect the angle
To scribe the next one into it, the first thing to do is bisect the angle of the walls that the skirting will be fitted to. I do this every time, in case it isn't exactly 122.5°. The quickest and most accurate way to do this is by using an angle finder, like in the picture. When you set this tool against the angle, it automatically bisects it perfectly.
Once found, set the mitre saw to the bisected angle.Click here for more help bisecting angles
Next, grab another piece long enough and cut the angle but like with a normal corner only go through the moulding.
Use a square to mark a line on the face of the board from the end of the cut on the moulding to the bottom of the board. This will help cut the next part right (you can use a compass to scribe skirting board like the normal corner above if the first one is cupped).
Turn the skirting board upside down and set the saw to the original angle, that the first board was cut to.
Step 3: cut the face:
This is the cut I used the jigsaw for to scribe skirting board into a normal corner. This time I cut down through the flat face of the board taking the back of the board out at an angle. Cutting the back out of the skirting like this ensures it doesn't get in the way of the first board already fixed to the wall. If you want to be sure you can adjust the angle to remove a little more out of the back, you can use a handsaw if your miter saw won't do the angle/depth of cut.
Step 4: remove the waste:
Finally, use a coping saw to continue cutting all the way through the moulding too. It's important to maintain the same cutting angle when removing the waste from the back otherwise it will prevent you getting a tight fit. If in doubt remove a little more - it won't be seen once the board is fixed (don't remove too much the board may split when you fix it though).
It should look like this!
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