# Calculating Fall for new Patio (Beginner)

Discussion in 'Landscaping and Outdoors' started by JBird, May 25, 2020.

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1. ### JBirdNew Member

Hi All,

Any advice on calculating this correctly would be of great help.

I have a space of land that is 31.4ft(l) by 9 ft (w). I want to patio this with slabs and have been trying (and failing) to figure out the correct fall needed from the top to the bottom for drainage.

I have read that the ratio is 1:80, with my calculation coming out at 11 inches from top to bottom.

I am using the following patio slabs: http://www.stonemarket.co.uk/product-bourton-riven-garden-paving

Any help calculating the fall is really appreciated!

2. ### ramseymanScrewfix Select

A fall of 5 inches over the 31ft length is approx. 1 in 80

3. ### ramseymanScrewfix Select

Better to tip it away from the house over the narrower 9 ft width if you can - that's about an inch fall

4. ### JBirdNew Member

Thanks Ramseyman.

Out of intreat what would a 10m (l) ratio be?

5. ### AbrickieScrewfix Select

Seriously ? Whatever device youâ€™ve posted with has a calculator, divide by 80

125mm