patio fall

[marsaday]

can anyone help me out with the falls ratios.

i have a patio which is going to slope from the house to the grass in one direction only. the distance from the house to the grass edge is 6m. what fall do i need ? currently i have done it to allow a 2cm fall.

is this enough. not sure what 1;40 actually means. is this 1cm for every 40 cm ?? i am stumped a bit and i think i have not made a big enough fall.

 

[holmslaw]

The fall you describe is 1 in 300.
6mts = 6000mm and 2cms = 20mm, so 6000 divided by 20 = 300. ie. for every 300mm the fall is 1mm.

I think thats a bit shallow, I'd go for 1 in 150, so over 6000mm that would be a fall of 40mm.

And you really need a drain to take the water away.

 

[marsaday]

if i dig a channel into the grass and fill it with gravel, will this be enough to drain the water away?

what will happen if i do a patio with a shallow fall like this ?

the spirit bubble will be at the back of the line and so it will be draining ok.

 

[holmslaw]

Your channel idea sounds ok.

A 1 in 300 fall will drain, the main problem would the difficulty in maintaining the fall whilst laying the patio. But if you're very careful and use slabs with a complaetely flat surface it should be ok.

 

[noseall]

if i dig a channel into the grass and fill it with gravel, will this be enough to drain the water away?

It may last a couple of seasons. Maybe.

It will depend upon your sub-soil drainage. A foot deep channel of gravel will clog up after a couple of years.

A well built soak-away can last in excess of 25 years.