Hi all,

We have a 1930ish house which had blown render on the rear wall (the
whole wall!)

I've removed all the render, revealing that the lower half of the wall
is brick, and the upper half bath stone.

About 25% of the stonework is blown with a crumbly surface, which looks
a right mess. I've mechanically removed as much loose surface material
as I can.

The brickwork had peeling paint (which was rendered over, go figure why
it blew) which I've removed using a poly-abrasive disc in an angle
grinder.

Question is, how should it be re-rendered? Lime or cement render? How
best to stabalise the surface so the render won't just fall straight
off again?

Is PVA a bad idea as it'll stop the stone breathing?

We've already had one quote to get it rendered and the bloke
recommended a cement render with an additive that supposedly sticks it
to the wall more effectively than PVA.

Any advice would be welcome.

Tony

tony.jackson wrote:
Question is, how should it be re-rendered? Lime or cement render? How
best to stabalise the surface so the render won't just fall straight
off again?

Is PVA a bad idea as it'll stop the stone breathing?

Use 1:1:6, as you've got the paint off there should be
no need for PVA. Make sure the wall is dampened before
the render is applied, and that it does not dry out
quickly. I wouldn't use lime mortar outside in this
situation, and neither would I use cement render which
is too bliddy hard, especially as used by the "cement,
plasticiser, sand" mob. Use washed sharp sand or
"rendering sand".