Sealing interior sandstone wall.

[maldivemoment]

mid Way through a renovation. We’re making a feature wall of the chimney breast which is predominantly sandstone. we’re keeping it exposed.
Wall has been re pointed both interior & exterior. We’ve given the internal wall a coat of sealant (only 1) but it’s still pretty dusty/crumbly. By that I mean if you run you hand over it, a fine layer of dust from the wall will come off. This also means that there is a fine layer of dust/v fine sandstone on the hearth & wood-burner on a daily basis.

Any top tips as to how we can completely seal the internal wall.

Thank you in advance

Sandstone chimneys are very porous and need to breathe. You shouldn’t be trying to seal it with waterproof sealant. I hope you did not repoint with concrete? That will trap water in the sandstone and cause leaks/mould/damp.

If the chimney isn’t being used, you can put a down vented cap on the top to stop rainwater coming down it, and you can use a wool chimney plug to stop warm air from escaping up.

It was not repointed with concrete.

What did you use as a sealant?

I remember seeing a water-based emulsion like a matt varnish for this job but it's not common.

The flue must be internally ventilated top and bottom to prevent condensation.

We used to call it "stabilising solution" and I see Dulux make a translucent Stabilising Primer for dusty walls, but ask their technical help desk if it is suitable.

Searching "wall sealant" tends to bring up silicone waterproofers, which are not what you want.

The issue isn’t rainwater or heat escaping. Chimney is in use.

I'm more looking for advice on how to stop the wall being all dusty every day.

Oh! Not sealant then. Per piglet John the stabilising solution is what you want. It’s often used as a primer before painting masonry, but it’s sold as a “stabilising solution”. That will bind it and stop the dustiness.

Thank you all. V much appreciated 👍🏻

The sealant we used was natural stone floor sealer.

You may need to use another coat of the same. How is it thinned?

Can I ask what sealant please op? I need a natural stone floor sealant. 😁