Tarmc over existing badly worn tarmac

[ck-]

I wonder what advice anyone can give. We have contacted a reputable local contractor who has suggested that rather than dig out and lay a new drive from scratch, they could simply lay new tarmac on the existing base (sma actually, as we have a tight turn into garage, so sma seemed better bet).
The problems as I see them are:
1) How good is the existing base to lay on to? It has been down for many years, but it is badly worn away - several inches of worn surface in some areas.
2) How deep is the existing base? Is it going to be good enough, or will it continue to degrade underneath the new top because it doesn't have enough mechanical strength?
3) The drive had large trees near to it: these have been cut down, but the roots are still there. The contractor has stated that the roots are better left alone, but I'd have thought better to get them out, as they will eventually rot away and cause subsidence
4) How well will the new tarmac bond to the existing surface, and how much of the existing surface would need to be scraped away, because it is very loose? I can kick the surface away quite easily with my shoes.
5) There is an amount of excavation that needs to be done to some parts anyway, because we are having a new section added as a parking space by the garage. Surely it is better to have it all built to the same depth and standard.

I had thought I was right to say "Rip it all out and start again", but after re-reading this site there seems to be a point of view that says "If you have a well consolidated base, then use that." My problem is that I don't really know how good the existing base is.

So of course I have probably shown my total ignorance here, but any help will be gratefully received.

Oh, and one final thing, I had suggested somewhere in between these as a good standard, given that there will be card from next door passing over it on a regular basis, aswell as our own traffic, and there is a 90 degree turn into the garage space.
Light Use Drive Access / Carpark
Surface 25 30
Binder 50 70
Sub-base 150 225
Dig Depth 225 325

[rab1]

post a picture mate, it`ll help the lads help you

[ck-]

post a picture mate, it`ll help the lads help you

Hmm, I'm struggling to know how to upload the pictures. Do I have to upload them to a website of my own and link to them from here?

[msh paving]

yes that the way to post pix MSH

[Dave_L]

Nothing wrong with an overlay of a fresh surface course.

Any areas that are badly worn/sunk/defective are relaid with a binder course

Area is swept clean of any loose stone/surface/debris

Tack coat emulsion is applied to the surface to 'bond' the new surfacing to the existing

If you really want to start afresh tell the contractor to requote!

[ck-]

Nothing wrong with an overlay of a fresh surface course.

Any areas that are badly worn/sunk/defective are relaid with a binder course

Area is swept clean of any loose stone/surface/debris

Tack coat emulsion is applied to the surface to 'bond' the new surfacing to the existing

If you really want to start afresh tell the contractor to requote!

Thanks Dave_L, I'm happy to pay for what is needed but really I'm asking people's advise as to what is needed. No point paying for something that will make the job worse!
I have some pictures here. Sorry they're a bit blurred, but I think that you can see the overall size of the driveway. The really badly degraded parts are at the bottom of the driveway next to the pavement.
This is the overview.



This is to the right of the garage where the old drive is heavily buckled (6 inch lift) due to tree roots, and the old flower border will be removed and a parking space taken all the way to the wall.



You can probably see the buckling better here, and you can just see the old edging strip. The new drive will extend right to the wall.



This is at the bottom of the drive by the pavement. Almost in the middle of the picture is the remains of the old stone wall. That bit has stayed at the same height while the drive has eroded around it.
The contractor did say they would dig out there to remove the stone.



This again is at the bottom of the drive by the pavement, and is not much more than loose stones.



The stones laid on the drive show the border with our neighbour's property - they have access over our driveway. As you can see, the contractor has just laid a course of edging on top of the existing tarmac, and then will apply tarmac to fill to the level of the edging.



The only quote I have is a number written on the back of a business card, and I have told them they cannot start on my drive until I get a proper written quote.

Thanks again for any help, and I'm sorry if these pictures are too big!

[Dave_L]

I can't see the pics?

The 'quote' you have is laughable.

You are doing right to hold off until you get a proper written spec.

[ck-]

I can't see the pics?

The 'quote' you have is laughable.

You are doing right to hold off until you get a proper written spec.

The problem with the pictures not being visible was that my home web server had been turned off

I gleaned some information from this site, and put together a list of why I thought a full "rebuild" is correct. Central to my argument is that they do not know how deep the existing base is, and so can't possibly know whether it is adequate. All through our discussions I have stated that I want a written quote, and I wrote what I thought was a reasonable spec, and gave it to them.

Here is what I have written (and I am grateful to this site for the vast majority of the material):
Tarmac drive
The standard specification for a Tarmacadam driveway, is given in the picture below.

... picture missing....

A wearing/surface course may be laid over an existing surface. This is known as an "Overlay". The overlay surfacing should be a minimum 25mm thick and MUST be bonded to the existing surface with a cationic or anionic bonding emulsion, commonly referred to as a 'Tack Coat'.

It has been suggested by <name withheld> that the driveway is compatible with being overlaid, rather than digging down and building from scratch. While this may be an initially cheaper option, it is only cheaper in the long term if the driveway is suitable. The key considerations are:
1) What is the depth of the existing sub-base
2) What is the state of the surface, in order to guard against reflective cracking.
3) How well can the organic matter on the current driveway (moss, leaves, etc.) be removed.

Tack Coats:
Tack coat is a browny-black emulsion of bitumen that is applied to the prepared, existing surface before laying the new surface/wearing course. The emulsion bonds to the existing surface, and then the new wearing course will bond to the emulsion, ensuring full adhesion. It also helps ensure that water does not find its way between the new and existing surfaces where it can freeze and lift off the new surface. The tack coat is absolutely essential in all instances of overlay work.
Tack coat is typically spray-applied to the existing surface at the rate of 0.4 to 0.6 litres per m². The keys points are that the coverage should be complete, ie, no 'bald' spots, and there should be no pools of liquid on the treated surface.

Laying an Overlay Surface:
The surface to be overlain must be clean and sound and free of organic material or other detritus. If the new material is laid over a badly cracked concrete base, old flagstones, or any other unsound base, any joints or cracks will soon be transmitted to the surface of the new driveway, and the surfacing will fail. This phenomenon is known as "Reflective Cracking" and is a well-documented problem for all overlay surfacing.

It is my belief that overlay is unsuitable for the following reasons:
1) We do not know the depth of the sub-base, and hence cannot be sure that the driveway will be adequately supported. The highly irregular surface at present would tend to suggest that the current sub-base is inadequate.
2) There are clearly visible cracks, caused by tree roots, which will continue to move and hence reflect through to the finished surface.
3) The current topcoat is extremely contaminated by organic matter, requiring a great deal of effort to totally remove it.

I require the driveway to be built to the following standards:

Excavation:
The surface needs to be dug off to a depth of at least 225mm. The depth of dig can be roughly calculated as somewhere between a light use driveway and an access road / small carpark, for which the following depths are suggested:

Light Use Drive Access / Carpark
Surface 25 30
Binder 50 70
Sub-base 150 225
Dig Depth 225 325

All weeds and other unwanted organic matter, along with topsoil must be removed and any soft spots excavated and filled with compacted sub-base material.

Edgings or kerbs MUST be used on free edges, i.e. those parts of the perimeter of the surfaced area not bounded by walls or other solid structures that will act as a retainer for the asphalt. This is to prevent it crumbling at the edges.

Sub-Base:
The sub-base layer is the main load-bearing layer of the driveway, designed to evenly spread the load of the traffic to the sub-grade below. A well-constructed sub-base will prevent settlement and channelisation - the phenomenon common on cheap installations, where two 'ruts' develop in the paving. These 'ruts' are caused when a car travels over the same line of paving to the garage, every morning and every night. The sub-base is intended to prevent channelisation and settlement.
For this reason, the sub-base specified in the above table is the minimum required. The finished sub-base should not deviate from the correct level by more than 10mm, and should reflect the final profile of the driveway.

Binder Course (Base Course):
This is a load-bearing, strengthening layer of the pavement. The binder course material should be laid and levelled out reasonably level (± 10mm) and thoroughly rolled and compacted before proceeding with the wearing course.

Surface Course (Wearing Course):
This is the top layer of the driveway - the layer that is seen and which takes the traffic. Given the amount of traffic, and the amount of turning that the driveway will be subject to, the surface course material will be Stone Mastic Asphalt (SMA), a dense, tough, durable asphaltic material reinforced with fibres, laid by machine.
The surface course should not deviate from the correct level by more than ± 6mm, and there should be no roller marks in the finished surface. A minimum fall of 1:80 is required for tarmac areas, although a fall in the range 1:40-1:60 is preferred.

[ck-]

The contractor has agreed with the spec I wrote, and I have witnesses to them accepting it.
We are in rather a peculiar position because the neighbours have right of access over our property, but the drive isn't shared ownership. Once onto their land, the drive is in much better condition, and is suitable to be built on top of. So they are having theirs overlaid, while we are having ours completely relaid. The contractor came to me this morning and said he had considered overlaying part of ours, but it seemed more sensible on reflection to dig it all out, and that is what his quote is based on.

Mine is being dug down now, and he has stated that they'll dig down until they are happy with the ground beneath before they start to build up again. Looking at how far down they have dug so far, they are clearly good to their word!
The driveway is about 80 square metres, and has 30m of stone edging with a price quoted of £3200, which is similar to other quotes we had.

I'll post some pictures of the completed job. Thanks Dave_L for your help.

Thanks to the owner of this site. Is there an option for contributions to its upkeep?

[lutonlagerlout]

send it to meeeeeeee!!!!

joking aside its that rare that anyone wants to give there is no facility
you could buy the gaffer's book

details here

well worth a read

LLL :;):



Edited By lutonlagerlout on 1286466232

[pickwell paving]

have a look on the about us page at the top of the website and there is a donate facility on there

[lutonlagerlout]

my bad
LLL

[pickwell paving]

sorry LLL only noticed it because I was having a nosey around the other day

[Mikey_C]

the gaffers snail mail address is on here and I think he accetepts, good old queens english pound notes, if you can't fit them all in standard envelope try a jiffy bag

[lutonlagerlout]

i hear his favourite colour is red re: notes
LLL :;):