Lime Plastering Advice and Recommendations

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Robert Nash

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I'm renovating my daughters bedroom with an 1894 Victorian semi-detached.

At the moment I've had to go back to brick on all the walls as the plaster was blown. The walls were is a bad state and various blends of plaster had been used by the looks of it.

Given that the house has a solid brick wall I want to add IWI which I believe should be breathable which means lime based.

So the first questions has any one had experience with thermal insulation?

I am considering either thermal board; thermoblok or spacetherm or thermal lime plaster; diathonite, thermopor or ecocork.

Has anyone had experience with any of the above and how did you find working with it?

Given, that it is a big area and lime plastering the whole room is both time and material I'm wary of cost.

So the second questions is whether or not anyone has experience of plastering the 3 internal walls with gypsum; wet of base and board and blending with lime of the exterior wall returns?

The third question is has anyone had experience of applying a scratch coat and then boarding with a breathable board such as fermacell?

Finally, should I just use the standard gypsum and wet plaster the whole room and have use thermal plaster board with a vapour barrier?

Thanks in advance
Is it a cavity wall, or solid brick construction because many were. Also was it damp or condensated in the first place .
A word of warning if your gonna dot and dab insulated board give it a coat of insulating plaster first before you dab otherwise it will condensate behind the board .
Try googling Tellings lime they have a great system called unilit they're insulation mortar unilit 20 comes up to a great spec with less thickness
Thermaline plus or thermaline super for me the thickness depends on your budget 48mm work out at an ok cost on the plus...i never used the others u have listed...if its tight around your window reveals use a thinner board or cut down point in your lime saving is more important.British gypsum thermaline and knauff version have vapour check in the boards so no worries with them just dab all round edges and a few in the middle
Thanks guys for the advice.

The room is a bedroom and it is a solid wall. Thermally I am concerned with the outside wall as the room (house) is hard to keep warm.
I do not suffer damp in the bedroom on the outside wall but the chimney needs some remedial work. The pots aren't capped. The pots are going to be capped and the chimney will be repointed and made good with NHL5 lime mortar.
The outside walls of the house and the chimney will then be treated with Stormguard to help prevent moisture penetration.

I have replaced the ceiling and insulated between the joists with Rockwall and going to use RSB to help reduce noise from the room above, attic.

I don't generally like dot and dab, as I want to try and do what's right by the building. So am leading towards wet plastering with the possibility of mechanical fixing of boards over the top before skimming.

I am vary wary of controlling moisture and putting a vapour barrier board up on the external wall will force the moisture somewhere else. Not sure whether I'm being paranoid of not. In addition by boarding I bring the dew point to the inside of the solid wall and not the outside so again I'm not sure the long term effect on the solid wall.

Now I remember being told that thermal breathable insulation on the inside with a breathable wall was the best for the house. The movement of air keeps the wall dry and protecting the mortar from moisture.

So not sure of the different merits... Clearly drylining + GP is the most cost effective but I don't know the long term impact on the house. Remembering that I'm just the custodian of the house at the present time and have a care of duty to house for the future.

Basically, I'm not comfortable with short terms fixes. As I been taught do it badly, do it twice.

Cheers Guys.
...not yet - I'm about to attempt to do so in a a month or two. I'm a complete novice, and I've been dithering between and for a few months! I'm going to go for the Ty Mawr approach, mainly because I've been offered some at a good price by the cob specialist who's repairing a wall for us. Knowing me, it'll be as slow and bumpy process with lots of requests for advice!
I've never bother putting continuous dabs top of board...this fire safety stuff is a load of b*llox, if there's a fire theres a f**king fire, not going to make any difference. Waste of adhesive.
Each to there own mate ...I try to do it as is stated by the people who make the products .
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