Sandstone Problems

[Johnmelad502]

Started a job painting round a bay window today and as I removed flaking paint, patches and lumps of sandstone came away. Pictures below:

2nd and 3rd pictures are of a wall that has not been painted before.

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

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• Johnmelad502
• 5 Mar 2010
• 1

Once the sandstone has dried out, is there a viable way to stabilise it prior to putting on the primer/undercoat.

If it's not that simple, what is needed?

Cheers

 

[dave1953]

Bit difficult this one Johnmelad,I had the same problem on an old cottage built of Purbeck stone,I think water had permeated the stone and frozen and blown the face edge off in various places.[It had all been painted before] I used SBR to seal and let the stonework breathe but left it for 2 months to dry out before I sealed and painted it with micro porous exterior paint. All fine for 12 months then a couple of small areas blew again so I re- treated and re-painted.I think it's down to really letting the stone dry out before sealing and to be honest that could take months if it's bad.
In picture 2 that downpipe isn't venting venting onto the flat bay window roof is it?
By the way the job I'me on about has had no more comebacks and I did it 3 years ago now but I am now very wary of doing something similar again as water and stone don't mix well in the long run.

 

[Johnmelad502]

I used SBR to seal and let the stonework breathe

What is SBR?

 

[dave1953]

Rubber based as opposed to Pva water based,Band Q sell it,about £14.00for 5 litre tub