Rendering a Bath stone wall?

[tony.jackson]

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

[Chris Bacon]

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".