Laying new foot or two of sand under tarmac drive?

[Jimlad]

Having just lifted 40 sqm of tarmac drive in prep for new block paved drive, there is well over a foot of grit sand under there (maybe even 2ft ?)
We will start digging down to remove sand (as laying everything from scratch)

300- 600 maybe more of sand under surface layer of tarmac.

If the sand goes down and down to maybe 3 feet or more is it ok to build the level back up to where I (originally) wanted my sub base layer to finish- to 250mm nelow dpc ? (build back up with mot type 1)???? A little advice please chaps this is out of my small experience - thanks.

[rab1]

could be shot down in flames here as i`m not a pro but dig out the first 200mm of sand and then compact. then lay terram down (woven fabric) to stop your type one migrating and then stone up compacting in layers.

[Jimlad]

I think you are probably spot on mate, and to other forum users - I'm sorry about the crappy title and description of my problem, it was late on and I was ruddy tired, and don't think I communicated the prob very well.

However; on further investigation today - the sand turns out to be the actual sub course layer - we dug down 3 and a half feet and still the same soft silty sand/soil.
I have ordered 14 cubic metres of mot1 and hiring a digger for tomorrow to clear the soft stuff to around 450mm-500mm below DPC and build up a good solid base, then throw down some non woven geo membrane (type NW8) from a guy at combined harvesters (find them on tinternet.)
This should - as you rightly said separate the sub course and sub base - and then I'm going to stick some more NW8 on top of the sub base (mot1) to sperate the bedding layer of grit sand from the mot (sub base.)

I could be shot down in flames here as well, what do you reckon guys?

[rab1]

a bit overkill mate, providing you compact the sand and leave enough depth for the type1 you should be fine.

Also remember that the lads giving advice on here are working full time as well but someone will always make an effort.

[haggistini]

I would remove all the sand/soft ground and back fill with type 1 in layers of 150mm compacted with a whacker peace of mind for the cost of sub-base and you got a machine at hand... Watch for services at that depth tho!

[GB_Groundworks]

weve done jobs though where theres still sand at 6metres down.... that was chewing through 10mm thick sheet piles so sands not all bad.

remove a good 300/400mm depending on how bad the sand is. can you squeeze it in a ball in a tight fist does it consolidate well? if its ok one blinding layer of roadbase say 40-100mm ontop of your geotextile then compact and consolidate, then your 20-40mm mot on top of that to level make sure you compact well but without pictures or seeing the sand its very hard to say....



Edited By GB_Groundworks on 1320780696

[Jimlad]

Chaps thanks for your advice, Rab 1 you may be right with it being overkill, but as its only my second drive I'm especially keen to do the job well and although it's a pain in the rear it's all good experierence for me,
My customer is very happy that I am pointing all this out to him (and also pleased that he's going to have a proper-strong drive) so he doesn't mind paying the extra for all the hardcore and fabric, labour etc...

Lucky I have a good customer eh - bet they're not all like this.

At the moment my plan is to dig down to 500mm below dpc with 1.5 tonne digger at £50 quid for a day, level and compact the surface best I can - and build up layers of mot1 up to 250mm - 200mm below dpc. (compacting in layers as I go)

Then the usual mot layer, grit sand and 50mm marshalls tegula on top, job done - I hope!

Job is in clipstone mansfield, notts and it's known in this particular mining town to have very silty sandy weak soil.

Thanks for your opinions people keep em coming, cheers, James.

[Jimlad]

ps. yep sand sort of consolidates to a ball if manipulated, is a darkish soil/orange colour but mostly sand not soil - we have also found a lot of builders waste in the ground, bricks - polestyrene metal etc so maybe the builders just chucked alot of thier waste under this particular drive wen building this 1980's estate?

Thanks again, will definately report back with pics and finished results for those who are bovved, cheers.

[lutonlagerlout]

Personally i think digging that much out you are wasting your time
sand is a decent sub grade if it is old and untouched
we did one in luton similar and we used geogrid which is like a heavy duty plastic mesh that we laid on at 350 deep then built the type 1 up in 100mm layers
I have about 150m2 left if you fancy a drive to luton?
cheers LLL

[Jimlad]

LLL thanks for the offer - and I would certainly want some if I had time, but really really pushed at the moment - got to dig down tomorrow all day and chuck into skip, then haunching and bed preperation for the edge courses if I get time.

I presently have alot of some non-woven premable membrane called NW8 from a company called Combined Harvesters based in Liverpool,the NW8 is a kind of white fleece but fairly thick, firm-ish and rough to the touch -(bit like me) probably medium duty stuff I think.
They say it'll be more than suitable and only £28 for 30sqm.

Very good of you to offer tho fella - thanks

How much did u want for it? If I need some in future( and you had none left) would you mind telling me where you got it from and how much?

I'm going to stare at everything tomorrow when on site and decide for sure how far to dig, thanks for your reply to post. cheers.

[local patios and driveway]

I would agree with lll. If the tarmac has ben o top and assuming no issues, why dig so deep. The geotextile will be the key in his particular job

[lutonlagerlout]

I paid £200 for 200 m2,used roughly 45-50m2 on a job so would take £75 just to get it out of my blinking way
has to be cut with a grinder
cheers LLL

[haggistini]

What about a 200 base of lean mix concrete ?