Driveway foundations

[Big G]

Not sure whether this post should be here or in gardening (or somewhere else).

Our tarmac driveway needs widening. I’m going to steal 3 foot from the lawn to do this. Not sure yet what I’m going to use as a topping for the extended bit – may use concrete; tarmac or block paving. The length of the extended bit of drive is about 40 foot.

My plan is to dig out the lawn about 8 inches to a foot deep, lay hardcore, ballast, etc and then top with 4 inches of concrete. The excavated soil from the front garden will be going into a rather large hollow in the back garden.

First question relates to the foundations. I’ve got stacks of rubble in the back garden. Mainly concrete blocks that are the 1930’s equivalent of breezeblock (12 inch by 6 inch by 8 inch) – and very heavy. Also got some 2 inch thick concrete that was laid as a base for a shed.

Finally, got lots of bits of sandstone that has been ‘mined’ from under our living room – long story but it looks like at some point an air raid shelter was put under our living room. The sandstone from this is currently under our dining room and will need to be moved/removed at some point in the future when I put a new radiator in.

Can I use any of the above as a base – probably along with a few jumbo bags of ballast from Wickes?

Questions on the pros and cons of concrete, block paving and tarmac to follow.



Many thanks in advance

Gordon

 

[noseall]

any "clean" hard core will be ok. clean as in no reactive products such as tarmac, red ash etc.
you will have to sledgehammer the rubble into smaller pieces as this will settle better. top it off with a layer of mot, this will fill in the cracks and provide a level substrate ready for the finishing material.

once mot is in place you will need to mechanically compact either with a wacker or vibrating roller.

if you decide to tarmac, leave the hard core down 60mm.

concrete 100-150mm down.

block paving, 100mm down.

 

[Big G]

Cheers for the answer. I'm pleased I can use the existing stuff I've got - even though it will take ages to break up as it's bloomin' hard. It will save me on skip hire and on the cost of buying hardcore.
Just need to buy a wacker now – Screwfix do a 10lb one. Could hire a petrol vibrating plate but as I will be doing the work a few hours here and there, this isn’t really an option.
I think I may be going down the block paving route. Just need to investigate what is involved.
One (thick) question though – what is mot? Is this the same as ballast?

Cheers

G.

 

[2scoops0406]

Cheers for the answer. I'm pleased I can use the existing stuff I've got - even though it will take ages to break up as it's bloomin' hard. It will save me on skip hire and on the cost of buying hardcore.
Just need to buy a wacker now – Screwfix do a 10lb one. Could hire a petrol vibrating plate but as I will be doing the work a few hours here and there, this isn’t really an option.
I think I may be going down the block paving route. Just need to investigate what is involved.
One (thick) question though – what is mot? Is this the same as ballast?

Cheers

G.

MOT - or MOT type 1 or correctly DTp Type 1 is commonly used as a sub base which is layered over the top of the sub grade (usually the hardcore) it is an unbound material consisting of fines (dust) and solids when compacted the mass interlocks forming a rigid surface which in the case of block paving may have sand layered on top, and then blocks placed on this.

See here for loads of info.