Underboard ceiling with coving...

[Egremont]

I want to underboard a 4x4m ceiling in a room with original coving (9.5 or if necessary 12mm board). Heaven forbid I have to get someone in to skim it, so I'd be looking to tape + hide the joins. As for the coving, as suggested sometime, somewhere I want to run some kind of board edging about 20mm from the coving and board within that - painting the outer perimiter + coving a different colour to give the impression of an extended coving profile. This would be better than burying part of the coving in plaster, however the original idea may have involve some skimming.

Q1: Any thoughts on the right edging as most stop-end I've seen assume a few extra mm for the skim coat. Can you get an exact fit for 9.5 or 12mm board, then again if the edge has a 90 degr bend-back (over board surface) would this show?.

Q2: In this day and age of 'Smoothover' and the like is there still no easier way to conceal the joins than to use jointing compound and sanding?. I've used this with reasonable results in the past but this job is something of an afterthought in a newly decorated area and I really don't fancy the dust!. Then again, given some of my past experiences with skimming I'd at least want to option of sanding as a last resort if all else fails.

Any comments on feasibility (or otherwise) welcome...

Egremont.

[Egremont]

OK well according to the British Gypsum site they do a 12.5 mm PVC end strip without the preformed 'arris' (I believe the cockney rhyming slag is 'rolf') for the jointing material.Wickes have something similar (just sold as PVC strip not particularly for plastering), though at 2.4m these are a bit short.

So I have a possibility for the heavy 12 mm boards, however plan A is to try and make do without edge strips - I wouldn't expect edges on a ceiling to get knocked much, but getting the dead straight edges might be tricky. If this fails plan B is to slip the edging in after the boards are screwed up. Somebody also thought of 'mitring' boards at the corners such that the edges are all papered, which should help.

As for finishing the join, looks like I'm sanding in time-honoured fasion. I'll go for multiple layers to keep sanding to some minimum, but I still expect to get covered in white dust!. Somebody also mentioned that applying several coats of thick primer paint also helps to hide blemishes, and I'll paint the boards up to the margin where the filler will go first to help with the sanding process.

Might not be what some would do, but in the true spirit of DIY at it's stingeiest it'll be much better than what I have for a lot less than a 'spreader'. If I get to do this before the reply-to button gets turned off I'll tell how it went...

Egremont

[Egremont]

If anyone else ever tries this...

I've finished this job, and I think the end result was pretty good - certainly a big improvement. I didn't use any edging [I might have done if I'd used 12mm boards], I just very carefully lined the (square) board edges up parallel to the coving about 1" away - you can't see the joins, honest!. I was lucky that the coving edges were fairly straight, an added bonus is it's hard to see the outside back edge where the boards meet the ceiling. I did the perimiter boards first, with plenty of screws round the edge (after fixing to joists first, extra screws into the old laths to support edge). Then put up the middle boards. Rather than mitre the corner boards, I just used brown paper & strong paste to go over the unpapered board edges (making sure there were no folds). Like everything else, the paper edges get caulked in with joint filler later. Perhaps the corners are a bit sharp, but (at least for the coving I had) the extended profile looks fine now it's painted.

BTW, I had a soft plastic squeegee-type tool (for tile grout) which I found helpful for smoothing out the (Wickes) joint filler after first applying with a trowel. It took several itterations, but the result was good with minimal (but sadly non-zero!) sanding down.

So there you go - yet another success for Egremont and uk.d-i-y, though all in all it took a few days.

Egremont