What is this - Indian Sandstone
Discussion
Hi All
We have a sawn and smoothed Indian Sandstone patio. We have cleaned it (using chemicals) but these marks remain. The marks almost look like the slabs are retaining moisture, but can't see how that could be the case.
The slabs were laid last year.
Each is on a full bed.
The back of each slab was primed with a slurry mix
NORMAL LOOKING SLAB
Which is how the majority look
SLAB WITH STAINING
There is one large area where multiple slabs look like this.
The marks don't brush of there is no residue.
We have a sawn and smoothed Indian Sandstone patio. We have cleaned it (using chemicals) but these marks remain. The marks almost look like the slabs are retaining moisture, but can't see how that could be the case.
The slabs were laid last year.
Each is on a full bed.
The back of each slab was primed with a slurry mix
NORMAL LOOKING SLAB
Which is how the majority look
SLAB WITH STAINING
There is one large area where multiple slabs look like this.
The marks don't brush of there is no residue.
Edited by rossyl on Tuesday 6th May 06:57
Do you find that the area with staining has standing water when it rains?
Previous house had similar staining on porcelain slabs which was due to the salts washing out from the bed the slabs are laid on and then being deposited on the slab when the water evaporated. That has the patio was over 2 levels and it was the lower one that suffered staining.
I did manage to get most of it off but it took quite a lot of cleaning. It ended up being a mixture of chemicals (I treated it similar to limescale) with lots of manual scrubbing and pressure washing.
Previous house had similar staining on porcelain slabs which was due to the salts washing out from the bed the slabs are laid on and then being deposited on the slab when the water evaporated. That has the patio was over 2 levels and it was the lower one that suffered staining.
I did manage to get most of it off but it took quite a lot of cleaning. It ended up being a mixture of chemicals (I treated it similar to limescale) with lots of manual scrubbing and pressure washing.
There's definitely nothing sitting on top of the slab (ie washed off from a raised bed, or standing water).
My thinking is this is capillary action, being drawn from below. But, with a slurry mix applied before laying, it's a bit of a mystery.
I don't know what the best thing we can do is.
My thinking is this is capillary action, being drawn from below. But, with a slurry mix applied before laying, it's a bit of a mystery.
I don't know what the best thing we can do is.
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