Damp looking sandstone

Marvel · 17 Jul 2012

Hi. I was hoping someone in the know could help me diagnose a problem with my external wall. I live in a mid terrace built in 1901, the external wall is built of sandstone. The problem is some of the brick look damp and there's parts flaking off. The house has been painted for as long as I've been living here, 9 years.

Any help appreciated

Untitled

Marvel
17 Jul 2012
1

Untitled

Marvel
17 Jul 2012
1

joe-90 · 17 Jul 2012

Probably the unusually wet weather. Wait for it to dry out then repaint it.

Marvel · 17 Jul 2012

hmm. It's been like that for years

I've repainted it before and it keeps flaking. I'd like to sort it once and for all if I can.

joe-90 · 17 Jul 2012

You'll need a damp course then. It's damp inside the stone causing the trouble, you can't sort that from outside.

canter71 · 17 Jul 2012

joe-90 said:
You'll need a damp course then. It's damp inside the stone causing the trouble, you can't sort that from outside.

Sorry Joe but rising damp is a myth!
http://www.architectsjournal.co.uk/...a-myth-says-former-rics-chief/5204095.article

joe-90 · 17 Jul 2012

In your opinion. Did that geezer speak up when he was with RICS? Nah - he was interested in his fat salary.

peaps2 · 17 Jul 2012

Just another angle on it.

"Older buildings were made from a mixture of stone and brick with a lime mortar. The Radyr stone and the bricks used in these structures are breathable, i.e. they let water vapour pass through them. However, the conventional masonry paints that we now use to cover these surfaces when they are starting to look a bit tired (or just for aesthetics) are not breathable. This means that any moisture within the stone and brickwork is effectively sealed in. Hydraulic pressure is a very powerful force and so when water needs to escape from the stone or brick it will do so and this is done at the expense of your paintwork."

http://www.sustainablebuildingresou...eling_off_external_stone_and_brick_work/1255/

Hope that helps.

Possel · 19 Jul 2012

That pointing looks like cement-based to me. That's impervious and it cracks, so any water on the face can get behind the cement but can't get out. So it goes through the stone and, when it freezes, the water in the stone expands and makes the surface loose. An old building needs lime-based pointing so that the water evaporates through the pointing not the stone. If you're lucky the cement won't go too deep and you can replace it with the proper stuff.

Marvel · 19 Jul 2012

Still not really sure what the best thing to do is. If it is rising damp wouldn't the bottom stones be wet too, they look dry to me. I'll definitely repair the big flaky patch, with maybe a lime mix and repaint.

Marvel · 19 Jul 2012

Possel said:
That pointing looks like cement-based to me. That's impervious and it cracks, so any water on the face can get behind the cement but can't get out. So it goes through the stone and, when it freezes, the water in the stone expands and makes the surface loose. An old building needs lime-based pointing so that the water evaporates through the pointing not the stone. If you're lucky the cement won't go too deep and you can replace it with the proper stuff.

Do you think water would be able to penetrate the pointing even tho its covered with a few layers of paint ? Or maybe the blocks were wet before they got painted and have never dried out!

Possel · 19 Jul 2012

Marvel said:
Do you think water would be able to penetrate the pointing even tho its covered with a few layers of paint ? Or maybe the blocks were wet before they got painted and have never dried out!

Cement pointing will crack as it's rigid, whereas lime is flexible. Thus a gap can appear along the edges of the pointing, then water can get in but it can't get out. New paint will not have filled those gaps for long.

Have you checked your tiles, gutters, downpipes, flashing etc above the spot? If the lower stone is dry it implies that water is getting in somewhere.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Damp looking sandstone

peaps2

Possel

Possel

Similar threads