DIY Doctor UK DIY Forums

Hi folks. As part of my building extension planning proposal I intended to create a soakaway to accomodate the extra surface water. However, the groundworks have revealed that the site is almost all heavy clay and shale. (The garden is about 3 foot higher than the extension's dampcourse) Its clear that any soakaway will simply back up for any inclement weather other that a light shower. Building Control appear indifferent to this and seem quite content for me to proceed with a very time consuming and expensive arrangement that will simply not work. Has anyone had a similar expirience and if so was any alternative acceptable solution found?

if the ground is potentially unsuitable then you need to carry out a percolation test and then this will allow the required size of soakaway to be determined. Thus if it turns out that the required size is unsuitable for the garden area you can argue the point with building control. Guidance on how to do the percolation test and determine the soakaway size is found in approved document H, which can be freely downloaded from the planning portal website.