DG27 Questions

[CHRIS]

Has anyone used the Bayosan product DG27 as a primer onto gypsum plaster board? I have been looking at Mike Wyes website and this looks like it maybe the thing I need, I have a modern plaster board ceiling I want to cover in a lime plaster skim to have an even finish with the original ceiling the other side of a steel beam.

http://www.mikewye.co.uk/dg27tech.htm

Has anyone succesfully used lime plaster on plaster board with this as a primer and do you get many cracks that need troweling over later, also do you use normal skrim tape or hessian on joints?

many thanks

 

[MDE]

I've used DG27 on a mixed background, including gypsum plaster (but not boards), to even out the absorption rates before lime plastering. Don't know about boards, but my guess is that you need to prevent any movement of the underlying material or else the lime plaster may crack (but perhaps less so than gypsum plaster). You could just use gypsum plaster, of course.

 

[BMcD]

Yes I have used it on plaster board ceilings and so long as your board work is ok with staggered joints and the length of the board going against the run of the joists and screwed up tight so you have no play in the board (so don't peirce the paper surface with the head or leave the head proud) you shouldn't have much problem. I scrimmed my joints with fibre tape prior to applying DG27. Jute/hessian scrim would be too heavy with the lime since there is little suction and is likely to fall off (very messy and annoying especially when a long length peels off and hits you on the back of the head). Talking of little suction, give youself plenty of time between laying on and scouring up as it will just hang there for ages.

But it seems fine now and no reports of any cracks and they were done a few months ago now

 

[ajbaker]

I have just finished plastering my bedroom with lime. One wall had been covered with plasterboard with acoustic insulation behind. This I did in lime simply to ensure a matching finish. Used DG27 on this as advised by Mike Wye. Also used the product to put a skim of lime on an internal wall that had been plastered and papered previously. The paper did not leave a clean finish so decided a re-plaster was the easiest option. I used self adhesive jointing tape and left over acoustic sealant for the joints and screw heads.

Its difficult to say how effective DG27 has been since I know no different. However I have seen no cracking or any other problems so can say it has not caused any problems at least. Go for it!

Also, I took Mike Wye's advice on the different mixes for different surfaces and again this has proved to provide a good finish.

I can testify to BMcDs experience though: it will take the plaster ages to begin to harden and carbonate on plasterboard. What took an hour on mortar took a day or two on plasterboard. Not a problem, just give it time.

We gave the finished plaster several coats of rich limewash - again this may well have helped to prevent cracking.

Good luck.

 

[Penners]

I'm interested to know why you need to prime plasterboard before using lime plaster on it. You don't need to prime it for gypsum plaster - the paper surface is specifically designed to be plastered.

 

[BMcD]

Penners wrote:

I'm interested to know why you need to prime plasterboard before using lime plaster on it. You don't need to prime it for gypsum plaster

Not all gypsum plasters will adhere to plasterboard either. There are only a few that will such as board finish, multi finish and bonding. This is probably due to plasterboard being a low suction background and therefore a bonding agent is required if the plaster is unsuited to low suction backgrounds

 

[CHRIS]

Thanks for the ideas, I will order some next week. I bet it is a fancy mix of PVA and fine sand or like! but I can see why lime would need a key on plaster board.

thanks

 

[ajbaker]

Chris.

Absolutely. That is the first thing that struck me when I opened the tub - PVA. Or more accurately, the glue I used to use in primary school which must have been a variation on the same theme!

Neat, it has a very thick consistency. I watered it down down to a consistency more appropriate for painting (I think it said it could be on the tub but not on Mike Wye's web site, or vice versa). I then 'painted' (slopped?!) the relevant walls. I wouldn't concern yourself with a neat finish or even a lot of wall showing through - that's not the point of it. It then has to be left for some time but you'll get away with less (I gave it 12 I think).

Good luck and let us know how you get on.