Indian Sandstone

[mark242010]

Can someone please explain what this may be? Initially I thought it was efflorescence but I’m not so sure now.

Thank you

 

[foxhole]

Has it had any sealer on it? , it’s very porous .

 

[mark242010]

No nothing put on it. Thanks for your reply

 

[simplesteve]

Is it newly laid? Maybe without the slurry coat being put on the back of it to stop it sucking the water out the mortar?

 

[mark242010]

Yes it is newly laid. Been down a couple of weeks. If that was the case will it be permanent or will it eventually disappear?

Thank you

 

[simplesteve]

Tbh I don’t know if it ‘dies down’. I do know it’s a problem especially prevalent with I.S., and the couple of times I’ve laid it I’ve always slurried the back the first.

The front also needs treating, or you’ll be forever trying to clean the green algae off it that always seem to grow on it. ( or maybe that’s a West of Scotland / damp/ geography issue)
Unfortunately, I’ve yet to see an I.S. installation that still looks good after a couple of years.

 

[Mike13]

It is where the mortar is not fully bonded to the sandstone, it has slumped/shrunk or been shaken away from contact with the underside of the stone, so moisture is getting in. If they had used 5 dabs it would be circular marks, possibly laid a little wet.
Most likely will stay like that now.

 

[efunc]

Did you watch it being laid? Was it laid on a full bed of cement right to the edges? Or a dollop in the middle of each slabs? You may have voids underneath if so and water collecting under the edges. That is my guess.