Woodburner - wall finishes options

2bamum · 1 November 2019 at 7:12PM

Hi,
We are in the middle of converting our conservatory into a more useable room and have decided to install a 5KW freestanding wood-burning stove in the corner of the room. One wall is brick (which we are leaving as a feature wall) the other wall is currently block work with an opening for sliding patio doors. There is a steel above the opening. We need to decide how to finish the second wall. I would render the wall but the plasterer has said we would need to fix steel mesh on the steel so the render can be fixed onto this and that an aluminium beading would be used to join the plasterboard from the sliding door recess, to the render. This all sounds logical but expensive. Fire resistant plasterboard which has been skimmed would be much easier but I have read that it does crack. Reviewing old threads, people have suggested fibreglass wallpaper or vitas plaster. Has anyone used these? Could the plaster product be used on a large wall?

FreeBear · 3 November 2019 at 9:00PM

2bamum wrote: »

Fire resistant plasterboard which has been skimmed would be much easier but I have read that it does crack. Reviewing old threads, people have suggested fibreglass wallpaper or vitas plaster. Has anyone used these? Could the plaster product be used on a large wall?

Gypsum plasterboard, fire resistant or otherwise is not rated as "non-combustable" due to the paper coating on either side. Once skimmed, it will crack and flake off if exposed to temperatures above 50°C.

Cement board skimmed with Vitcas heat resistant plaster will work. Not cheap though. I finished my chimney breast off with lime plaster, and only have a couple of very fine hairline cracks. Temperature close to the stove is pretty extreme (have seen it up around 120°C). Not many plasterers will want to work with lime, and few will want to use the Vitcas stuff either. Would advise against using steel mesh - It will expand at a different rate to any plaster and cause it to crack.

2bamum · 4 November 2019 at 10:13AM

Thanks Freebear, I really appreciate your feedback.
What is mix for lime plaster? I knew lime was used in render as it allows for thermal expansion but hadn’t seen info about line plaster.
Why don’t plasters like working with these products?
Also on the Vitcas website they say you have to use their boards but will any A1 rated cement board do?

FreeBear · 4 November 2019 at 11:28AM

Lime mix for internal plastering - Three parts sharp sand mixed with one part lime putty. For base coats add animal hair or screed fibres (I use TDP 20mm fibres). For a smooth fine finish, a thin coat of two parts fine marble or chalk mixed with one part lime putty.

With both base and top coats, stir the putty well and add in the sand slowly. Small quantities of water can be added as required. If you add too much water, leave it to stand for a few weeks and then pour off the excess - Lime putty mixes will keep for ages as long as it is stored in a sealed tub with a layer or water on top of the plaster.

As to why plasterers don't use it - It requires quite a bit of work. To get some idea of what is involved, take a look at the series of short videos of Ty Mawr https://www.youtube.com/watch?v=DmWQ1X1jYOk&list=PLFSqOXpgBEL7HsP_j3HQv1YQzwrbhJDLi - Dot'n'dab then skim, you could probably do a whole house in a day. To plaster a hose in lime, you'd probably be looking at a week and then leave the building for six months while the plaster cures.

I have used cement board (and plaster board)as a backing for lime plaster where heat resistance & finish was more important than breathability. Saves quite a bit on time.

Woodburner - wall finishes options

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