Can you re-tarmac over old tarmac

H

Henny Penny

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... or do you have to dig up the old stuff first? My neighbour had a bad tarmac job done a few years ago where the tar was not hot enough and the tarmac was layed orignally and now the tarmac is ravelling. What can she do? Does she need a civil engineer to advise?
 
It would be best to get rid of the old dodgy stuff and lay the new stuff on a properly prepared formation, saves problems with lifting kerbing , gullies manhole covers etc etc.
 
Agreed, laying new over old generally requires the old material to be scarified in any case to give a bond, am I right? And scarifying is a smelly, dirty and dusty job, especially near the house.
 
Spot on Carpenter , Scarifying is also expensive , minimum hire rates would apply also need a dumper/truck to haul away scarifyied material & dump costs, get a JCB and small dumper. Cheaper , cleaner and you are paying for what you get instaed of 4 hour min hire for a job that may take 1 hour.
 
I not sure I agree with this. Scarifying (or road planing) is mainly used for the purpose of lowering the existing level in order to create falls for drainage or to ensure that the finished level with the new macadam ties in with existing features such as kerbs etc.

Even when new roads are laid, macadam is normally laid in layers without scarifying in between. Often there is quite some time between the layers being laid (for example almost every housing estate in the country).

The only special treatment of the lower layer required prior to laying the upper layer is that it is cleaned and in some cases sparyed with a 'tack coat' to aid adhesion.

There is one circumstance in which the lower existing layer would need to be removed. If it is structurally inadequate. In other words, if the existing is ravelling, then just overlay it. If it is settling (and maybe ravelling as a result) then dig it out, recompact the granular sub-base material adding more granular material as necessary and start again.
 
Adding new on top of old is not good practice if it puts the new surface at less than 150 mm to the top of the damp proof course.

I have always taken the view that if you want a good job then the base must be done properly, and putting a couple of inches of new tarmac onto a poor base is not a good job.
 
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