I have just had a new patio laid using Marshalls Firedstone paving slabs. Before laying, all the slabs were uniformly coloured in a buff yellow.
Since being laid and once the grouting was finished, there is now a load of dark patches all across the patio. some of the slabs look as they did before laying but the majority look as if they have a damp patch on them that needs drying out.
I've seen the efflorescence posts and that seems to suggest a white salty appearance on the slabs, but my slabs have dark patches on them so I'm not sure this is the issue.
Sometimes slabs can have damp patches for a long time after laying as the cement cures in the bedding course. This appears as damp looking blobs and lines alongside the edges. Could this be it? A photo would help.
It's been over a week since being laid now. Here's a picture. The original colour is the light yellow colour on the top right hand slab. The brown patches on the other slabs should not be there.
It'll be like that off and on for a few weeks or even months, depending on the weather. The cement takes a long time to finally cure. Once the slabs, bedding course and pointing reach the same moisture content you won't see it any more.
