planning regs re rainwater off a roof

daheff · 08-06-2015 01:29PM #1

Are there any regs that say you have to siphon off rainwater into a drain?

My issue is that we have a mid terrace house without access to a drain at the back of the house. Wondering if we are required to drain rainwater away or just let it wash into our garden?

**when I say we have no access, we could access it by digging up 2-3 neighbours gardens on either side. However of those 2-3 neighbours theres an "awkward" one on either side between us and the drain...so technically no access

sydthebeat · 08-06-2015 01:54PM

the rainwater discharge should be dealt with in the planning conditions for the house.

Strolling Bones · 08-06-2015 03:24PM

In this situation one often needs to build a soakpit which in simple terms is a pit dug in the garden then filled with stones. Best to employ an engineer to design it.

daheff · 08-06-2015 03:42PM

sydthebeat wrote: »

the rainwater discharge should be dealt with in the planning conditions for the house.

But in terms of where I am adding an extension that would be within the exempt size, would a soak pit be the best solution? Roughly speaking how big/deep would this usually be?

BryanF · 08-06-2015 03:52PM

daheff wrote: »

But in terms of where I am adding an extension that would be within the exempt size, would a soak pit be the best solution? Roughly speaking how big/deep would this usually be?

What will the size of your remaining garden be ?

Strolling Bones · 08-06-2015 04:05PM

daheff wrote: »

Roughly speaking how big/deep would this usually be?

There IS no roughly speaking. You have to have an engineer design it beacuse the affect of the soakpit on other structures has to be taken into account.

No one here can do that.

daheff · 08-06-2015 04:46PM

BryanF wrote: »

What will the size of your remaining garden be ?

I reckon it'd be approx 6m *5m

Strolling Bones wrote: »

There IS no roughly speaking. You have to have an engineer design it beacuse the affect of the soakpit on other structures has to be taken into account.

No one here can do that.

Ok let me rephrase. Can somebody indicate what size soak pits they have seen elsewhere are?
I understand an engineer will have to design 100%, all I'm looking for is an indication so I have a rough idea how big it'd be.

Strolling Bones · 08-06-2015 05:49PM

I have seen a soakpit as small as a domestic fridge - and as large as a family car.

Calahonda52 · 15-06-2015 06:06PM

OP, can u explain the current set up a bit more and amplify your plans.
My assumptions.
What I think you have is a mid terrace house with a continuous gutter at eaves level along all the houses and the occasional down pipe.

You don't say if single or two storey.

You now want to build an extension so I am assuming the existing gutter remaining and all you are concerned about is the run off the extension.

So lets do the rough math
using rainfall from here
http://www.met.ie/climate-ireland/rainfall.asp

say the extension is 4m square on plan, then assume a 300mm overhang so the plan roof area is 4 by 4.3 = 17.2 sq meters

Assume your rainfall is 1000mm per annum then your annual rainfall has a volume of 17.2 public meters or 17,200 litres.

If concrete roof tiles, 75% of this might run off into a soak hole or rainwater harvesting [RHW] tank.
If the latter, using it for toilets, car washing and clothes washing only, then maybe store enough for 6 weeks, 1.5 months so a 2,150 litre tank would do, say 3,000 litre so at a metre deep would be 1.7m square.
My guess is the soak hole won't be much smaller so consider RHW

planning regs re rainwater off a roof

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