Lime skim over gypsum

[margatedan]

Hello all,
I've been a backseat viewer on the site for a while - this site is an amazing resource! I have a question - it sounds simple but I haven't seen anything on the site after searching...

We have a wall that has been half replastered in lime, but the other half (from before our time) is gypsum and finished with paint etc. The lime side is a little rougher and comes out a little more than the gypsum side so we'd like to skim the lot to get the wall more regular. My question is, can we skim lime plaster over gypsum? We have a pre-mixed lime plaster 3:2 strength that we'd like to use. Are there issues with movement etc with lime on gypsum?

Any pointers are welcome!

 

[Penners]

I'm afraid my pointer may not be what you want to hear, Dan, but I'm sure your best solution would be to hack off the gypsum plaster, then lime plaster that half of the wall, too.

 

[Keithj]

I'm no expert (5 years so far in the university of listed period property), but I tried to stick some lime render to gypsum - duly scratched and wetted first, and pushed on very hard, covered and kept damp. It fell off a few weeks later.

 

[margatedan]

Thanks for the replies. A local shop recommended this stuff as a primer for gypsum - http://www.mikewye.co.uk/product/dg27/ We shall see what happens! I'll keep you posted.

 

[FamilyWiggs]

Penners and Keith are right - it is unlikely to be successful as the gypsum and lime have very different suction properties. There is also very little point putting lime over gypsum, other than for aesthetics.

A better approach is to take off the cement and then lime the whole wall. Lime plastering is very forgiving of novices, hugely therapeutic, and very satisfying when complete.

Good luck - and post lots of pics!

Robin

 

[Nigel Watts]

I agree with Wiggsy.

 

[noj]

I would agree with the others, but I'd really like to know how effective the DG27 is (at someone else's expense!). Manufacturer's claims sound good

 

[margatedan]

Plaster's been up for a week or so, over the DG27. No signs of failure. It's quite an expensive to cove a large area though. Luckily we only had a couple of square metres to cover.

Yes - I'm going to try some DIY lime plastering soon. Around the fireplace. Would you recommend just dgetting stuck in? With some help from Youtube of course...