The wrong driveway material?

[Mr Punter]

If you are on clay soil you would need to excavate a vast amount and backfill with the granular permeable base material.  You may need to go down half a metre from the finish level.

 

I have laid permeable paving on a fairly thin bed of granite chippings on chalk subgrade and it drains very well.

[Alan Ambrose]

I’m going to respectively disagree - as I said our type 3 drive is working well. You can get a SUDs calc done, receive the volume you need to store, and then calc the volume of driveway that represents, bearing in mind the ‘void ratio’ or some such i.e. proportion of your drive that can be water. I’ve a calc like that here somewhere. Helpful if it can drain somewhere by gravity.

[Post and beam]

On 14/05/2026 at 20:13, Alan Ambrose said:

You can get a SUDs calc done

Who can do this please?

 

Scraping the crush off of our drive is enough of a job to be honest. Going down half a metre would be a nightmare.

My plan now is to scrape the crush away, lay a membrane, perhaps a French drain away towards the rear garden,200mm of type 3, compact. Then worry about what the top dressing will be.