Wearing coat needed for tarmac drive?

Hi Folks,

We have a pretty long driveway that we need to lay tarmac on. As its going to be fairly costly because of the length, we're looking to save money if possible (without compromising on longevity or anything structurally important!), so my question is:

If the 'norm' is to put say a 25mm fine wearing coat on top of 50mm base coat, is there any reason why you would not want to just use a single 70 or 75mm of base coat?

I'm led to believe that the finer wearing coat is more expensive but its main purpose is just cosmetic as it gives a finer, smoother finish. Our drive is on a fairly steep hillside as is, so I'm almost wondering if a slightly rougher finish might be advantageous for grip and its not the end of the world if its not a silky smooth finish! However my initial searching for construction methods seems to come up with the fact that roads do have the wearing coat.... so there must be a pretty good reason for it :-)

I'd be grateful if anyone could comment. TIA

Gareth

Reply to
Gareth Jones
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=============================== If you haven't already done so check here:

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's generally regarded as the paving bible and might give you a definitive answer.

Cic.

Reply to
Cicero

In message , Cicero writes

Thanks for the link, however I had already found that site - absolutely loads of good info as you say ... but unfortunately I couldn't find an answer to my question (although it did confirm that the 'standard' way of doing it was to have a wearing coat, but it didn't say what happens if you don't)

I even tried posting to the sites forum, however there seemed to be a problem with the script and it kept coming up with an error each time I tried to register :-(

Reply to
Gareth Jones

================================ We used to do domestic drives and the routine was always the same. A well rolled base with a layer of about 4" to 6" of 3/4" bitumen followed by a top coat of 1/4" bitumen. Each layer was rolled using a hand 'vibroll' (vibrating roller). The theory then was that the top layer of 1/4" bitumen was a water-proofing coat / frost proofing coat. I believe that there's some truth in this and that's also the reason that roads are finished with a fairly smooth top coat to provide water run-off.

I think it also depends very much on what weight roller you have available but I would think that you would need a fairly heavy roller to get anything like a driveable surface with just a layer of 50mm bitumen. As mentioned above I think you might need a finer finishing coat to prevent breakup from adverse weather conditions.

Cic

p.s. The finer mix (1/4") was always more expensive than the 3/4".

Reply to
Cicero

Block pavours (sp?)

longer lasting too

Reply to
Robbo

In message , Robbo writes

Lovely, but out of my price range I'm afraid.

Reply to
Gareth Jones

I've not seen any....pavements yes, roads are always 3/4 stone in bitumen, even motorways

Reply to
Phil L

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3/4" bitumen topped with 1/4" bitumen was quite standard for domestic drives and it tallies pretty closely with the modern specification as prescribed in the 'Paving Expert':

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"Tarmac Driveway

  • Excavate to reduced depth of at least 200mm below finished level (350mm below dpc) and cart all spoil to licensed, off-site tip. * Excavate any soft spots in sub-grade as required and dispose. * Supply, lay and compact minimum of 100mm of DTp1 crushed stone sub-base material to falls and levels. * Supply, lay and compact 50mm of 20mm dense base course bitmac, and 25mm of 6mm hardstone bitmac wearing course to falls and levels. * Clear all site of debris and rubble on completion and make good. * All Tarmac to comply with BS 4987"

The overall specification differs but the bitumen layers - 3/4" = 20mm and

1/4" = 6mm are more or less identical.

Cic.

Reply to
Cicero

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