I would appreciate some advice on how to rectify an issue with a recently installed patio.

I have tried to get the original installer to repair and rectify, but this has been going on for a good 18 months and is a very long story.

The nub of the matter is that the installer was an approved Marshalls patio slab contractor, that’s why we choose them.

The patio has been laid using sandstone Marshall slabs.

However, the steps have developed a problem which Marshalls say is cement leaching and the contractor says is effervescent staining.

Since installing the patio the contractor has been removed from the approved supplier list.

Anyhow, is there some way of using a sander to remove the staining and crusting?
I am sure it is cement staining, as it only occurs on the steps, and has washed the stain down onto the slabs etc.

It has been driving me a bit crazy trying to resolve this, as both Marshalls and the contractor are blaming each other.

Are you sure it’s not something biological leaching up from below?

You would be better with some chemicals to remove the staining but you would need to be careful not to take the colour out of the slabs.

The garden was altered dramatically for the patio.

The steps had to be dug out of the soil, and then built up with a brick and concrete foundation. The slabs were then cut and placed on top of this concrete / cement foundation.

The staining is very heavy and has a chemical crystalline appearance.

We have tried some solution recommended by Marshalls but it doesn’t touch it.