Starting out...first self build ever

[CAPTAINSAM]

Hello

This will be my first self build. I'm quite handy in terms of DIY. However, I need to ensure I've taken everything into account.

Basically I am building a single story outhouse no higher than 2.5 meters at MAX.

I need to know how far down I need to dig to lay the foundations and waterproof membrane.

Point to note:
My garden is lower than all of our neighbour's, so generally, all/ most of the water comes down to ours and there have been times our garden has flooded. In order to avoid this, I am thinking of either raising the garden bed by adding lots of soil, I do wonder whether adding some drainage into the garden leading back to either the gulley or our private manhole would be worth it? I do plan to plumb the outbuilding. Should I plumb straight into the plumb works of the outbuilding or direct line it to the gulley / manhole?

 

[JohnD]

You aren't allowed to run groundwater into a sewer.

You could dig a soakaway.

 

[CAPTAINSAM]

Thanks @JohnD I will look at building possible soakaway(s) as well as raising the garden bed.

Does anyone have any tips about how far down I should go for laying the foundations?

The building will be roughly 30 meters from the manhole. Therefore, I assume I will need to dig rather deep in order to achieve the require gradient for the waste pipe(s). Will probably have to hire someone to make the manhole somewhat deeper too. Having said that, should I just hire someone to do the drainage, conversion of manhole as well as the foundations all together or should it just be a case of manhole + drain plumbing?

 

[tomfe]

I suggest you do some more reading around both on here and the building regulations approved documents.

 

[jeds]

Foundations depend on soil. Usually minimum 900mm in clay but could be deeper if trees nearby. Standard floor would be something like 100/150mm of well compacted hardcore, 50mm sand, 1200g damp membrane, 80/100mm PIR foam insulation and 100mm concrete. The hardcore can be up to 600mm deep but must be laid in 150mm compacted layers - if more than 600mm you need to get advice.

 

[^woody^]

Building regulations for the drainage if nothing else comes to mind

If the garden gets flooded, importing a load of soil wont help, but will just create a boggy mess.

 

[oldbutnotdead]

What's the proposed floor area of this shed- sounds as if you'll need building regs for the drainage bit anyway so you might as well call them up, pay the fee and get their advice for the footings and everything else- BCOs aren't ogres (or the ones up here aren't anyway). Drainage- your run from your shed wants to be in as straight a line as possible and must join the manhole at invert level (not halfway up). Check the Approved Documents for detail on what gradient to run to, how much cover is needed, all that sort of stuff. If it is a shared manhole (ie discharge from more than one house runs through it ) then it isn't your manhole, it belongs to the water company and you'll have to talk to them as well.

Soakaway- your BCO will be aware of local soil conditions, he may instruct you to run rainwater from the shed roof into the main drains.

Boggy garden- if ground is suitable for a soakaway then great. If not (and it sounds like not) then think about burying one of those big 1000ltr plastic containers with a pump in it, running land drains to it and using the water to water the garden, wash the car etc. - of course, if you end up pumping it into your shed drain occasionally then c'est la vie