Rendering inside wall

jdpl28

Hi,

I had to strip back all the plaster on my walls cause it was coming away and there was some dry rot in the plasterwork. I'm going to put up dry lining on the walls as a new wall surface but the dry rot surveyor said to render the bare concrete blocks with sand and cement before putting up the dry lining. Should I do this? Is this really necessary to do on the inside? Will this prevent damp from permeating the walls?

thanks,
J

mad m

I think you mean rising damp as to dry rot? Did you get walls treated for rising dampness? I would do as the surveyor suggests as if you got walls treated by a company you will void your warranty (20years) if you don't do as they specify.

jdpl28

It's upstairs, so I don't think it's rising damp. Although there is a flat roof just outside. It is dry rot that he was looking at. Although not a bad case of it. It attacked the floorboards, but didn't seem to get into the joists, but it's all over the plasterwork.

thanks,

Mellor

A coat of lime platers would help control moisture problems.
Lime is naturally hygroscopic and regulates moisture in the air and surrounding areas. Dry rot cant form is moisture is at the correct levels.

jdpl28

Hey, thanks for that. So would you put in any cement at all? or just sand and lime? And would the lime be all "used up" if the moisture level was high for a long time?

thanks,
J

jdpl28

Also, just wondering, should I add any additives, like polybond to the render? Or coat the walls with polybond before rendering them? The walls are quite dusty at the mo cause of all the old plaster/render taken off them.

thanks,
J

mad m

jdpl28 wrote:

Or coat the walls with polybond before rendering them? The walls are quite dusty at the mo cause of all the old plaster/render taken off them.

thanks,
J

Absolutely without doubt,Yes! Give it 3 coats,very easy to mix and apply plus its fast drying...Watch those splashes though.

jdpl28

Just reading somewhere, that you shouldn't render old houses with cement, particularly with portland cement, cause it's too hard. Doesn't allow the house to "breathe" or doesn't allow any movement. My house is an old council house from the 1930's. Would this qualify? Would using polybond help?

thanks again,
J

Mellor

Mellor wrote:

A coat of lime platers would help control moisture problems.
Lime is naturally hygroscopic and regulates moisture in the air and surrounding areas. Dry rot cant form is moisture is at the correct levels.

The lime won't get used up. It absorbs moisture from the air, and releases it when needed. You shouldn't need any portland cement
It would depend on what the house was built out of to weither portland was suitable. But portland cement wouldn't do anything for the moisture problem,I can't comment to weither polybond should be used first, but lime render as a finished coat.

I found this for you on Lime mortar,

Lime mortar is not as strong in compression as OPC mortar, nor does it adhere as strongly to the masonry as OPC. The mortar is softer so more able to accommodate movement and thus less prone to cracking than OPC. The 'softness' and reduced adhesion of lime mortar can be beneficial when used with old bricks or masonry which tend to be themselves softer than modern bricks and prone to damage by harder mortars.
Lime mortar or mortars containing lime are more water absorbent than OPC mortar, acting to draw damp out of the brickwork or stone

jdpl28

thanks again for that. How do you make lime render? And is it ok to put insulated plasterboard over it? Would 1930's house generally be made of softer bricks? And would they be damaged by a hard mortar?