The Brew Cabin

Dear Tony

Glad to hear that your op went well. Hope you're managing to get some rest as well as answering all these questions!!

We have employed a contractor to lay some 85 square meters of Indian Sandstone Flags around our house. They have just completed two small sections but still have the bulk of it to lay.

They say that the fall needs to be 50mm in 2.5m, whereas we understood the fall should be 10mm in 1metre which is only half the fall that they are recommending. The problem is that a lot of the patios are in walled areas on two or three sides so the slope is very noticeable and gives the appearance that the wall slopes downhill. At one point we have measured a fall of 65mm over 1.8m. Is this correct and if not what fall would you recommend?

Chris May

Thanks for the good wishes - I'm feeling much better, although keyboard cramp is beginning to set in!

50mm over 2.5m is 1 in 50, which is not really excessive, but is a bit steeper than absolutely necessary for a patio. If you're prepared to accept small pools of water lodging in the low-points of the riven textured surface, then you can get away with a fall as low as 1:80, which is 12.5mm per metre, but I'd suggest somewhere between 1:60 and 1:80.

You have to find a balance between adequate fall for drainage, without it feeling/looking odd, and without the patio table inducing a feeling of sea-sickness. At the end of the day, the choice is yours - if you instruct the contractor to lay at, say, 1:75, then you can't complain if you get small, short-lived puddles after a downpour. Personally, I wouldn't be too worried about 1:75 :)

Many thanks for your reply. Wishing you a very speedy recovery, the paving industry and their customers need your sound advice to keep them on the straight and narrow!!