Garden Building - Rainwater Drainage

[sam8364]

Hi Chaps,

I want to build a large workshop/store at the end of my garden. The garden is long and narrow, about 4.25m . I would anticipate the workshop being about 3.4m wide with a total roof surface of about 20-24m2.

I am not sure about how to handle rainwater drainage from the roof. The current shed just runs off onto the ground - but it is considerable smaller. The workshop will be at least 30m from the nearest mains sewer. However, I am guessing there may be problems if it were just run off on the 0.4m strip around the building.

I considered constructing some sort of soak away but the regs seems to say that this cannot be built within 2.5m of a boundary (which all of my garden is).

So - what is the solution? Any thoughts please

Cheers

Sam

 

[joe-90]

Just let it run out onto the road.

You will have to make it out of non-flammable materials though.

And it has to be less than 50% of the garden area (I think).

 

[freddiemercurystwin]

A soakaway can be built next to a boundary but not within 5m of a building.

 

[sam8364]

Letting it run onto the road is not an option as it will be even further from a road than it is from a mains sewer.

I am not sure what you mean about needs to be non-flammable - do you mean the building construction? Why would this be so? Garden sheds, workshops and even garden offices are usually made of wood?

In terms of a soak away - can you run a path over a soak away or does the ground become unstable?

 

[RedHerring2]

Your workshop is not subject to Building Regulations if it's built of non-combustible materials and within 1 metre of the boundary.
If it's 1 metre or more from the boundary it can be built of combustible materials, i.e. wood, and still not be subject to Building Regulations, as long as it is under 30m ² floor area.
Therefore, strictly speaking, you can just let the water 'go to ground'.

Why not see if there is any ill-effect before you start laying pipes &/or soakaway?

My workshop is 30m ² and the water 'goes to ground' with no ill-effect.
There is a dpc in the wall and a dpm under the slab. I have a 250mm X 250mm shingle border all round the workshop at least 150mm below dpc.

If the soak away is properly constructed there's no reason it should become unstable and no reason why you shouldn't run a path over it.

 

[nickjb]

If you are planning of making it out of wood and less than 1m from a boundary then you will require building regs if it is bigger than 15m2

See last para here:

http://www.planningportal.gov.uk/england/public/buildingwork/projects/workcommonoutbuildings/

How about a rainwater harvesting system? Even if you just use it to water the garden it shouldn't be too tricky to build a system that will cope.

 

[sam8364]

Oh Blimey, good job I did not realise the 1m rule in relation to building regs. Good job you chaps are here.

So what does 'substantially non-combustible materials' mean in reality. Do we mean bricks and mortar/concrete blocks or would some form of treated or clad wood also work?

What is the definition of boundary? Does this include the boundary where our land meets the garden of a neighbouring property.

If there is a 450mm space all around between the structure and the boundary fence and I lay a decent depth of shingle around - should that be enough to act as drainage?

I had considered rain water harvesting but then there is an issue of either burying a tank or it taking up a large chunk of space.

 

[RedHerring2]

Oh Blimey, good job I did not realise the 1m rule in relation to building regs.

You're not the first and you can rely on it, you won't be the last. Two of our neighbours have contravened the regulation. In fact one of them even over-sailed the boundary with their wooden shed, by about 400mm. Their concrete slab over-sailed by about a metre.
I just built the fence with a slight dogleg in it, after bringing it to their attention.

So what does 'substantially non-combustible materials' mean in reality. Do we mean bricks and mortar/concrete blocks or would some form of treated or clad wood also work?

I suspect the concrete blocks/bricks are the way to go. Don't forget your roof will still be combustible. I can't imagine how you can make timber substantially not combustible.
I suppose you could do a mixed construction with the nearest walls to the boundary substantially non-combustible.

What is the definition of boundary? Does this include the boundary where our land meets the garden of a neighbouring property.

That's the one.

If there is a 450mm space all around between the structure and the boundary fence and I lay a decent depth of shingle around - should that be enough to act as drainage?

About 250mm deep with the appropriate fabric to suppress weeds and prevent the gravel mixing with the soil, I would try that first before buying/installing drainage/soakaway.
Check H3 1.13 of Approved Document H http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADH_2002.pdf

Especially check Eaves Drop Systems.

You could install guttering and drain that into your 450mm gravel border, or ..........

I had considered rain water harvesting but then there is an issue of either burying a tank or it taking up a large chunk of space.

A water butt is not covered by regulations. Use that to collect the rain water with an overflow to your gravel border.