The Brew Cabin

Posted: **Thu May 17, 2007 5:25 pm**

Hi, I'm just about to start a DIY paving project.
I want to do my drive in clays but I'm worried about movement.
My house is built on the site of an old victorian baths and I'm in the deep end .
My neighbour dug a test pit to see how far the his footings were down and had a shock at 32 courses! below the DPC.
All the backfill was topsoil which explains why when I built a 6ft boundary wall between our properties 3 yrs ago it's sunk by 1 1/2".
The drive has normal traffic, with occasional use by a 7 1/2 tonner.
Should I go for a deeper sub base than normal? Or is there anything else I should be considering.
cheers guys.

Posted: **Thu May 17, 2007 9:33 pm**

32 course isnt especially deep footings ,its about 2.5 m i did work in london in the early 90s and sometimes there were 40 course in the footings depending on the site datums
if you dig out maybe 350 mm below finished then use terram ,then 150mm of type 1 ,then wack,then 120 mm of type 1 then wack,then sand blocks etc
remember block paving is a flexible drive so even after this if it sinks an inch in 5 years ,you can always take the clay pavers up and do it again
mind you this is only what i would do ,a structural engineer would give you the full rundown
cheers LLL

Posted: **Sat May 19, 2007 2:26 pm**

LLL is right - excavate to around 500-600mm and use a geotextile over the sub-grade. Place, level and compact approx 150-200mm of Type 1 using a vibrating roller or a big, heavy plate compactor. Then, place a layer of geo-grid, and overlay that with another 150mm or so of Type 1. The geo-grid will substantially reinforce your sub-base and minimise any settlement for several years.

For an example of a geo-grid, see this site ... other geo-grids are available.

Posted: **Sat May 19, 2007 6:10 pm**

Thanks guys, this site is so good .
It's nice to see that people are willing to help out with advice for us novices.
I feel fairly confident of getting a good result having read your replies.
Now to start sourcing materials.

Posted: **Sat May 19, 2007 8:48 pm**

Keep us posted (pics would be good) as to how you get on, Morse (please)

The Brew Cabin

Sub base for made up ground