New parking area - MOT sub base?

[pixiepoo]

Hi

We’ve recently dug out a large parking area (18m x 7m). We still have a lot of landscaping to do outside and as such we don’t want to spend money on our finished topping i.e. gravel/tarmac etc until all the work has been done. We need something that is usable (to park and turn vehicles on) and will be fine for a year or two until the rest of the landscaping catches up.

We were given 11 tonnes of something cheap which was a mixture of dust and stone which was fine during the summer but now in the winter it is nightmare, holding water and makes a mess of tyres/shoes – it just basically doesn’t have a good ratio of stone in it.

I understand that before we have our topping gravel we ideally need to lay a sub-base of MOT type 1. If I buy a load of this and put it over our existing layer and do a really good job of wackering/rollering it, would this create a stable area for cars to sit on without sinking? Also, does it create a mess when wet? I know there has to be dust in order for it bind together but the stuff we have down at the minute you may as well be at the beach when the tide has just gone out!

Any help and advice appreciated

 

[^woody^]

Use scalpings, there is no dust.

If the base is holding water then you need to sort the draining below it out

 

[tomfe]

Get 2inch clean

 

[r896neo]

If its quarry dust or similar then you need to remove it. Putting mot over the top will not help. It will hold water and forever be unstable when water logged.

Mot type 1 or 2 will do as a parking surface, once properly compacted there will be little to no dust/ dirt come off it.

 

[tomfe]

Type 1 is impervious to water get type 3 or 2inch clean. It's not nice yo walk on but makes a very good base and is fairly cheap.

 

[pixiepoo]

Thanks for your replies. If I got 2inch clean would that wacker down at all or would it stay pretty loose everywhere?

I ideally want something that can stay there until we put gravel on the top of it, would 2inch clean be fine as a sub base to gravel?
Thanks

 

[r896neo]

You cannot use an unbound sub base like clean stone under gravel, they will just mix into one big soup of expensive decorative gravel and cheap grey stone.

Use type one or type 2. Type 3 is totally unworkable unless being laid in deep fills as it has large rocks in it and you need a heavy duty vibrating roller or road roller to compact it. A vibrating plate will just bounce off it.

Type one when used on the surface and heavily trafficked can be quite impervious but as a sub base it is permeable. So if you can have a fall on it and fall the bulk of the water away it will be fine. If not then you may need to go for type 2.

 

[pixiepoo]

Thanks r896neo - it looks like I'm back to MOT type 1 or 2 then, any advice on what depth I should go for on top of what's already there?
Just considering that when wackered we will 'lose' some stone in the softer layer underneath.

 

[tomfe]

If you are not worried about drainage get hogging.

 

[John D v2.0]

If what's underneath is unstable you'll need to dig it out before hand to get to undisturbed ground. I know that because we did and used a lot more hardcore, and the neighbours didn't and their drive is somewhat bumpy now. Failing that you might get away with a decent geotextiles membrane between the two then they won't mix and the load may be spread enough.

 

[r896neo]

As I said in my first reply, lumping more on top is a bad idea. You need to remove the existing layer of waterlogged quarry dust or whatever it is and use proper sub base. You may be able to mix a good chunk of it back in with the new type 2 but its hard to know without seeing exactly what it is like. If you leave it in there it will remain fluid especially under loading.