Why cant I use 45 degree mitres for fitting skirting boards?

[benjiman]

Hi all,

Im about to fit some new skirting boards but have been told by a builder friend that I cant use 45 degree mitres to join the internal corners.

He said I have to butt one against the wall and cut the other to match into it. 45 degree cuts will work so why cant I use them?!

 

[big-all]

proper way to do it is to scribe one bit of skirting cut to fit
the other bit neatly

having said that you can of course use a mitre saw

its as acceptible as mdf skirting or using no nails

youll find most people mitre

big all

 

[masona]

45 degree cuts will work so why cant I use them?!

Because no internal or external wall are 90 degree.

 

[benjiman]

proper way to do it is to scribe one bit of skirting cut to fit
the other bit neatly

having said that you can of course use a mitre saw

yup thats thats the correct way to do it, but it is very hard to get the right fits isnt it, even with the coping saw. Isnt there an easier way that will result in a better finnish?

 

[benjiman]

45 degree cuts will work so why cant I use them?!

Because no internal or external wall are 90 degree.

Yes but what if I were to sand the mitres so they did match up. Or use a angle measuring tool and then set the mitre saw to that degree and cut it?

 

[big-all]

yes it is difficult

try under cutting very slightly cut the strait parts with a normal
handsaw[ undercut as well]

this means when you have to adjust it you only have to work
on the front edge to make it fit

get 2 bits of skirting about a foot long with internal mitres one end
and external mitres other end to pair up so you can see how much
of an adjustment you need to make on the angle to make them fit

dont forget half the diffirance on each side of the cut

big all

 

[masona]

Yes but what if I were to sand the mitres so they did match up. Or use a angle measuring tool and then set the mitre saw to that degree and cut it?

You can but the wall got to be plumb as well as 90 degree, impossible unless you have perfect external or internal wall.

 

[2scoops0406]

Yes but what if I were to sand the mitres so they did match up. Or use a angle measuring tool and then set the mitre saw to that degree and cut it?

You can use an angle measuring tool, and a mitre saw, but remember that not only is it likely that the internal angle is not 90 degrees, it is also likely that the walls aren't perfectly vertical, therefore for a perfect fit, you need to cut a compound mitre, which is more difficult. For internals, it's best in my limited experience to profile and butt the skirting, for externals, of course you have no choice, in this scenario, you can either mitre, or possibly compound mitre the skirting, or pack out the skirting until it is vertical. At the mitre, I like to either pin the mitre with small stainless steel pins and mitre glue, or even better biscuit joint them, this helps prevent the mitres coming apart.

 

[AdamW]

Easiest way I have found is to cut a 45-degree mitre, fit the skirting and then use filler to fill the gap (if there is one).

I have never used an electric mitre saw, the one I have is a cheapo hand-version. I have found that it takes a while to get used to before you can cut mitres accurately, otherwise it tends to cut at a slightly different angle to the one selected.

The method I have described is only any good if you plan to paint the skirting anyway. If you want a varnished wood finish then it is no good! I did this AND filled any minute gaps between the wall and skirting with filler, and nail holes. Then sand smooth, prime and paint. The finish looked seamless, almost as if the wall and skirting was cast as a single piece.

 

[2scoops0406]

It's difficult to sand moulded skirting on internal angles, hence the butt joint method. Also with mitred externals, they tend to part company if filled with filler. Sure mitre as best as possible, slap some filler in, but 10:1 in wont last that long.

It really depends on how far out of true your walls are. I used to live in an 18th Centry cottage, cutting 45 degree mitres would have been an utter waste of time, seeing as the amount of filler required would have been massively excessive. In this case, I decided that the best finish entailed a case of packing out the skirting so that it was nearly vertical, compound mitres, pinning the mitres, and filling where necessary. It was time consuming, but at least the result was asthetically pleasing.

 

[big-all]

forgot to mention

if your using a mitre box or a mitre saw without fine adjustment
you can place slithers of wood underneath or behind the skirting
when your cutting it to give you fine adjustment of angles

you just move the slithers or wedges towards the blade or away
to increase the angle or decrease the angle
taking care as you finnish the cut to support skirting or it will jam
on the blade

big all

 

[ChrisR]

I'm appalled that nobody knows why you don't mitre skirtings , or how to scribe them! What do they teach ....??!

Wood moves - usually shrinks of course after it's been put in an ouse, at least it traditionally did before kilns etc.

That means that even a tight fitting mitre(of any angle) WILL open up and you'll see into the gap. Think about it - the gap will always be on the obtuse-cut side of the wood. (ie the 135 not the sharp 45) That means it isn't a problem on external mitres, only internal ones.

Ye olde solution is to "scribe" the internal joints, so one piece runs full section to the end wall and the other is cut round it. You pick which is which according to which way will give the least visible gap when the wood shrinks. So if it's the back of a recess, the line of sight to see into the gap would be parallel with the back wall - not where people tend to look from!

Cutting the scribe is easy if you MITRE THE END FIRST!! The wiggly line of the cut (135º) on the face of the skirting is exactly where you have to cut , say with a coping saw, to fit snugly round the other board. If the room isn't square, you just angle the cut so it's correct at the surface.

Easy when you know, huh!

 

[masona]

I'm appalled that nobody knows why you don't mitre skirtings , or how to scribe them! What do they teach ....??!

Erm er, it does explain above why you cannot mitre skirting and I have some 90 degree internal corner mitre in my property and hasn't open up in over 22 years, maybe I glued and pin it that why

 

[big-all]

ok explenation masona

skirting nailed to wall ouside mitre skirting shrinks across the grain
pulls the mitre tighter towards the wall

internal mitre outside edge is the shortest edge
shrinks 1mm towards wall on two planes[90%]
so it stands to reason internals loosen
externals tighten

clear as mud eeehhh

big all

 

[masona]

Yes, I know that ! Done carpentery for the last 34 years !!!

ChrisR said "I'm appalled that nobody knows" and that's including you as well !!!!!!!