Should I go the whole hog and go down the route of buying £200 of crates or use the rubble/bricks available to me to make a soakaway?

It will take water from a roof covering 45 m2, which means crates of around 1m2 OR 1.5 – 2m2 for rubble.
The permeable cover for the aggregate is £50 so I’m saving £150 buy using the bricks from our old extension and obviously it also means that we don’t have to get a skip or grabber lorry to remove them.

We’ll be staying in the house probably for at least 20 years and once our build is done access to the soakaway by digger will not be possible. I don’t want to be digging this out again in 10 years by hand at the age of 50!

Any advice from builders / landscapers or anyone that’s had one would be most appreciated!

The rubble would be ok so long as it doesn’t contain a lot of fines. i.e. when placed, the rubble needs to have sufficient voids to be able to take the surface water. %30 voids is a good place to start.

The advantage of crates is they give a much larger void ratio letting you have a smaller overall soakaway.

I would suggest that if serviceability is going to be an issue, wrap the lot in a permeable geotextile / membrane to stop the soakaway choking up later on.

I may well be wrong, but you might need planning for it? Could be worth checking out. For either method, the more important thing is using geotextiles around whichever infill you use to prevent fines ingress over time.

Soak-away design usually requires voids to be approx 30%. This is basically the volume of your hole x.3 which gives you a volumetric storage capacity. This may or may not be needed depending on the porosity of the ground (Please check it isn’t clay).

Random rubble should be okay for infill, however, you usually need to line the hole with a permeable membrane. Just ensure you buy a strong one as the bricks could pierce this and with time it can infill with fines from the surrounding soils and become less effective.

Check out BRE 365 for design guidance.

Just to add to this – there are a few questions that need answering – Whats the soil type? Do you know if the ground will take the water? Have you undertaken a soakaway test (dig a hole, fill it with water and time how long it takes to empty)?

i.e. if it is a clay soil any soakaway is unlikely to work!

if it is a clay soil any soakaway is unlikely to work!

Building regs round here specc’d a soakway for my neighbour. Its solid keuper marl (clay) all the way down – when it rains he has a lovely water feature pond now 🙂

Thanks for that chaps. It’s not clay and we’re going to get building control to have a peek inside the hole before we put anything inside just to make we’re ticking all the boxes.
By the sounds of it, once I’ve done the storm flood test and estimated the size, I’ll be OK with rubble and a membrane.

Building regs round here specc’d a soakway for my neighbour – when it rains he has a lovely water feature pond now

Sounds about right.

we’re going to get building control to have a peek inside the hole

Hummm…

once I’ve done the storm flood test and estimated the size, I’ll be OK

Make sure you do that test and repeat it a coupe times too. Flood the pit, let it drain then flood it again and then for a third time. This simulates successive storm events.

Had a stroke of luck yesterday! I came across someone who has to get rid of loads of plastic pallets. Stacked up and wrapped in membrane they’ll act just like the crates, but they’re free!

Thanks neilforrow, I’ll fill it three times to check the drainage.

Building control won’t let you use bricks anymore

Building Control will still let you use bricks/rubble!

I do anyway, and all of my colleagues as far as I know……….

Plastic pallets sound alright, just wrap them well, and allow plenty of cover, otherwise you could have a nice soft spot in the garden.

As long as you haven’t got clay ground, or a high water table, you should be fine.

And, make sure it is at least 5m away from any buildings!