Insulating Lime Hemp Plaster

[joncooper27]

I have an old stone property and I have some wall that have been stripped back to bare stone and I am thinking about plastering/insulating with lime hemp plaster at approximately 50mm.
This would keep the thermal mass of the wall and keep the wall breathable.
Does anyone have any experience of this? Did they need building regulations approval?

 

[Jacob]

I have an old stone property and I have some wall that have been stripped back to bare stone and I am thinking about plastering/insulating with lime hemp plaster at approximately 50mm.
This would keep the thermal mass of the wall and keep the wall breathable.
Does anyone have any experience of this? Did they need building regulations approval?

You won't need Building Regs.
If you google it gets a good write up.
I know people locally who have used it and sing its praises.
I'll ask them more tomorrow.

 

[sammy.se]

I've lime plastered my walls. Do you have a specific question on the process?

 

[joncooper27]

I want to insulate them with hemp.
The wall I’m doing comes under building regs as part of an extension.

 

[Jacob]

I want to insulate them with hemp.
The wall I’m doing comes under building regs as part of an extension.

Have you submitted plans and specifications?

 

[SLM]

When I did an extension and used lime plaster, from old to new, the building inspector wasn’t interested; it’s plaster, was his view.

 

[Jones]

I have used lime hemp from Ty Mawr lime in South Wales. It's a premixed hemp and slaked lime which takes a long time to cure and dry. It leaves a slightly textured wood chip like finish which I like or you can top coat it for a smooth finish. Insulation wise it makes a bit of difference and the walls feel warm so there's no condensation risk but it won't insulate as well as dry lining for example. I know the Ty Mawr guys do a cork based plaster which might be a better insulator I've never used it though.
You can also get chopped hemp and mix with a hydraulic lime and a bit of sand to make your own plaster which will cure a bit quicker than the slaked lime stuff. If you don't need a smooth top coat it's quite easy to apply with diy skills.

 

[pgrbff]

In Italy, you can buy premixed insulating hydraulic lime plaster. I used it around all the windows I made and installed to avoid condensation problems. It isn't hemp but it works and has approval in Italy. I have plastered in and out, approximately 1200m2 in hydraulic lime plaster.
In Ireland when I first started using lime, I plastered using hot mix fat lime which was much harder to use and took a lot of looking after.

 

[The_Yellow_Ardvark]

I think the used to use horse hair in the day.

 

[pgrbff]

I think the used to use horse hair in the day.

Horse or goat hair is for strength, not insulation.

 

[trvlr]

Lime mortar was much used and preferred in days gone by for its ability to breath, low expansion, and generally better than cement mortar. Lime plaster more than likely same reasons. Lime mortar also was naturally coloured by by whichever sand was used within it; and thus no need paint in the future.

 

[elstona]

Like @Jones I'm using Ty Mawr products extensively to renovate our house (parts of which date back to the 1700s). On the external walls that are a timber frame with brick infill, I've used wood TM's fibre boards as an insulating layer on the inside (lime hemp plaster to level off the wall to get a flat surface, then fibre board, then more lime hemp plaster and finally a finishing coat which is then painted with clay paint). OK, you lose 100-150mm off the inside of the room but it's been worth it.

 

[joncooper27]

Hi Elstona
On your internal walls approximately what thicknesses have you used of each product?
I was thinking of doing something similar just not sure on the board as well

 

[elstona]

Hi Elstona
On your internal walls approximately what thicknesses have you used of each product?
I was thinking of doing something similar just not sure on the board as well

Anything from 5mm up to 35mm on the base layer (medium hemp) to get the wall reasonably flat, then the wood fibre. Fine lime hemp of c10mm with a mesh bedded in next, finished with a 3-5mm coat finishing coat. I’ve used 40mm fibre boards on (reasonably thick) stone walls but 110mm on the single skin brick & timber walls.

Mike