Soak Away!

[theoldun]

oldun,
Are you sure it's not 30% voids for rubble?
.

Stuart, You are partly correct in what you say, as BRE digest 365 Design for soak ways for catchment areas exceeding 100ms do state 30% void, however as we work to the building regs formula for soak away design for catchment areas not exceeding 25ms, these state a 20% void.
Regards oldun

 

[ey143]

Thanks for this useful post, I've learnt a lot. I am having a mini digger dig up part of my large garden. I live in Watford where looking at the British Geological Survey of my area indicates we live in a upper chalk area.

I am paving about 20m square of the existing front garden and was going to install a crate soakaway to take water from the drain channels etc. What size soakaway should be sufficient for this task? The mini digger guy suggested just using a pit with bricks but I would rather do it properly now especially since we will be working on the house later and I'm sure this will help with planning permission etc if we have a proper SUDS scheme in place.

 

[Ollyfp]

In summary, the construction of a soakaway varies according to the type of ground your property sits on, hence, you should ask an experienced (and preferably old) LOCAL builder for advice!
In North Norfolk we hit free-draining sand at about 2m. Historically, a hole 1.5m x 1.5m backfilled with brick rubble and covered with DPM has always worked well in this area.
All the best!