Drainage for Patio.

K-Rod · 14 Nov 2008

Hi everyone.

I'm in the process of preparing part of my garden to lay a patio down and was wondering about drainage.

To put you in the picture, the area is about 3m wide by 9m long. At the far end is a metal shed on a concrete base which I'll be laying the patio flush up to, the left side is a rendered breezeblock wall, the right is going to be turfed and at the near side is a path then the house. Hope that makes sense.

I've been reading up about drainage and the recommended slope is 1 inch to 40 foot (?) so I figure that should cover me. But my question is, which way do I run the slope and how do I get surface water to drain/run away? Presumambly the slope would run lengthways, i.e. along the 9m length as opposed to the 3m width? If that's the case it'll either drain towards my concrete base or towards the path that's in front of the house.

Any help on this would be greatly appreciated.

K-Rod.

r896neo · 14 Nov 2008

you can fall it in any direction or combination of directions you like! In terms of laying and aesthetics it it is obviously better to just fall in 1 plane. You can fall it towards the grass if you like as i assume you'll have some edging seperating the two. Generally speaking take the water away from the house but it all depends how well and to where the path (beside the house) drainso?

noseall · 15 Nov 2008

any hard standing will drain towards a storm gully or otherwise.

ideally away from the property, but if a r.w.gulley is sited against the building then run it to the gully.

1/80 is adequate falls for a patio.

if the ground is poor draining then don't expect the garden to take sudden storm water or frequent winter rain. it will pond and get muddy/messy.

i have lost count of the times that we have replaced patios that had inadequate drainage. some people think that a 2' hole in the ground with a few bricks will do. or even a bit of pea gravel sprinkled along an edge!

a roof collects the same amount of water as a patio and they have large soakaways, so expect to dig something similar for a patio.

K-Rod · 15 Nov 2008

Thanks r896eno and noseall.

Yes I am going to lay some edging to separate the patio from the lawn but as noseall said I'd be worried about muddy puddles if I run it that direction.

I've never noticed any puddles on the path so presumably water drains adequately off the path. On that basis, would it be ok to slope towards the path and hope it can cope with any extra runoff, or should I not risk it?

I'm torn between the lawn or the path. Do I have any alternatives or workarounds anyone can think of?

Thanks again for any responses.

noseall · 15 Nov 2008

a path will appear to drain ok because a path only usually has itself to drain.

whereas a large body of paving that is sloping towards a specific point, is collecting water from many slabs and depositing that water in a small area.

you need a drain, and/or a soakaway. are there no rainwater pipe drops to the property, near to the patio?

K-Rod · 15 Nov 2008

Hi noseall,

All there is is a drain for the downpipe from the upstairs bathroom but this is at the opposite side of the path to where the patio will end (if you see what I mean).

Can you explain to me what a soakaway is please?

noseall · 15 Nov 2008

a soakaway is a large rubble filled hole in the ground into which rainwater is allowed to drain.

it must be 5m away from any building or highway.

a soakaway into clay is practically useless. in this instance rainwater is usually drained away from the building via a storm system or a combined storm/foul drainage system.

K-Rod · 15 Nov 2008

Right I've got you.

Thanks very much for your help noseall, I'll more than likely be back at some point for more advice!

deefadog · 17 Nov 2008

In my last house i had a similar sized driveway that i patio'd, i sloped it to 2 x drainage grids and had a pipe going to a large soakaway i dug, which was around 1.5 meters wide and about waist height. filled it with rubble stones and chippings and i never had a problem.

Also to get a good even slope i bought a level that had a gradient on there, so you just slide the cover over the normal level setting and lay the patio to the gradient one.

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Drainage for Patio.

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