Christian McArdle wrote in message 3f375d34$0$15038
No. Don't plaster to the bottom, or it will wick up any moisture or be
cracked when the floorboards flex.

The skirting should have a solid backing in case you have carpet fitted.
With voids behind it will cave in when the carpet is stretched

2. I notice from postings that some people have glued skirting - is
this really going to work with 145mm stuff ?

Sure it is. Gripfil is very flexible but you need to use it generously (one
cartridge per 4m)

No. Use screws if possible. Then your expensive and labour intensive work
cutting the boards isn't wasted when you need to remove the skirting to
install flooring or chase out electrical runs etc.

I'm guessing this has already been done.

with enough screws, even a warped board will be held
flat.

Nah, let the board sit where it wants and fill the gaps. If it isn't fairly
straight, take it back. There is no reason for quality skirting to distort.
Shrink it will, but twist it shouldn't. Trying to counter the stress in a 4m
board with fixings will only result in cracks.