india sandstone

I Have to grout a patio wich has riven sandstone slab with 10/15mm gap. I understand dry mix sand cement does not work for this type of slab and brush in product would be ideally. I came across Sika fast fix but load of comments about failure and product coming loose apart to be very expensive...

Hiya, I would like to lay an Indian Sandstone patio on my garden. I seen some patios that were lay without mortar/cement. What is better? With or without? And what the advantages and disadvantages? Really appreciate some advise from those who experience. Thanks,