So when we met with Matt the Builder - he asked for details about our soak-away. Our plans just showed a circle with the words soak-way, with no supporting information.
Our first point of call was Christian our architect but he pointed me in the direction of our Building Regs man Stuart. Here is Stuart's response.
Good Morning Tamsin,
The construction and design details of the rain water soakaway really depends upon the percolation of the ground into which it is situated.
When the footings are dug I can make a judgement call as to whether the soakaway needs to be constructed of crates (usually required in a more clayey ground) or could be a rubble filled pit with a terram topping (in more shaley/stoney ground).
From previous experience of the area I would be fairly confident that a rubble filled pit or pits would be fine, but a cant give you a formal answer until I know the actual ground conditions on your site.
There is another issue that could affect the soakaway design and that is whether you have a planning condition applied to your permission, which may require the soakaway to be designed in accordance with the relevant BRE digest. I would recommend checking your planning permission to make sure that it does not have a condition on it relating to rainwater disposal. If it does then you will need to get a design done by a drainage specialist or a structural engineer. This is more likely to be a crate type soakaway design.
Hope that helps.
Stuart Anderson C.BuildE MCABE
Building Control Surveyor
I will take a look at our Planning Permission to see if there is a condition attached relating to a soak-away.
Watch this space.