- Thread starter dyndns
- Start date
Answers to 1: cement renders are not impermeable, painting them with a 'waterproof' coating will inevitably trap moisture in the render and could lead to problems down the line. Also, waterproof paints contain plastics and using them will inevitably introduce yet more microplastic into the environment as the coating weathers.
Answer to 2: if you DIY IWI, it might be cost-effective in the financial sense but you'll need to do a proper analysis of heat loss and energy savings to find out
Answer to 2: if you DIY IWI, it might be cost-effective in the financial sense but you'll need to do a proper analysis of heat loss and energy savings to find out
Yeah, agreed with Jamest, even if I had a wall covered with a cement render that I was unwilling to remove, I would still choose to lime plaster on top of it and paint with a breathable paint. In my book, the less layers of modern junk on a wall, the better.
In terms of options for internal insulation on cold solid masonry walls, yes there are many well-tested approaches. Look an breathable boarding options like wood fibre, expanded cork, or wood wool boards. Another option is an insulated lime plaster applied thickly to the wall.
In terms of options for internal insulation on cold solid masonry walls, yes there are many well-tested approaches. Look an breathable boarding options like wood fibre, expanded cork, or wood wool boards. Another option is an insulated lime plaster applied thickly to the wall.
Ah, thank you. How interesting, I always assumed cement render would be impermeable but it's good that it does 'breathe' a bit. Thank you both for the answers, great to hear there are some cost effective ways to insulate too! I wonder if there are any sheep wool-based options - wool is such an amazing product warm, fire resistant, renewable..
Yes there are members here who I believe have done sheepswool stuffed between studs and then faced with wood wool and lime plaster. Not sure how they are doing with it. Search the forums a bit.
Nice!
stuart45
Member
- Messages
- 777
- Location
- Somerset, England
It depends on the mix how permeable cement render or pointing is.
Generally a 3/1 sand/cement mix is close to being impermeable, but using a 6/1/1 sand/lime/ cement mix is similar to NHL3.5.
Some plasterers used a 5/2 scratch and 3/1 top coat, whereas others went for a 5/1/1 scratch and 6/1/1 top.