Another thing that is defeating me

How big are these gaps ? funnel web size or daddy long legs ? If they are bigger than 5 mm I would coat a packer like ply in the gaps, then push it in - or fill the gap with cornice cement - be sure to trowel it off and tidy it up immediately though.

Usually I mark a line on the wall the height of the cornice and put a temporary nail every few metres, this gives the cornice something the sit on and makes it easier to align correctly. I mix the cornice cement until it is a toothpaste consistency and apply a 10mm bead along both edges of the cornice, rest it on the nails and press in firmly. If it does not stay in place I will add some additional temporary nails along the ceiling. I then use a small trowel or my finger to smooth out the cornice cement. This leaves no gaps.

The biggest issue I have is getting the cut for the mitre the wrong way, stuffs up everything.

Andrew

Originally Posted by Bargain Hunter

The biggest issue I have is getting the cut for the mitre the wrong way, stuffs up everything.

Andrew

to stop that happening using a miter box and a scrap piece of cornice
I cut both ends of and internal corner and both ends of the external corner
and then would use that as a guide so that i cut the correct angle

forgive the southerners mate,lol. Ive done the cornice cement thing on a few large gaps in timber. It works pretty well cause it goes off quick and doesnt sag . Just got to make sure that it is wiped off for a smooth finish or its a bastard to fix later. But gooing up a packer works well too, but it can still slide out of the gap before going off.