The dark art of road surfacing

You would be well advised to call on the knowledge and skills of trained professionals if you want an asphalt-surfacing job completed properly. At Martin Cowman Ltd we use two different methods of laying tarmac: machine lay, aided by the use of a paver finisher, and hand lay where material is placed manually. There are various factors that determine whether a job will be machine laid or hand laid. These can be things such as tonnage or area of the job, accessibility (hard to manoeuvre a paver in tight spaces) or plain economics.

Step-by-step essentials for hand-lay work

  • Material delivered on purpose built insulated delivery lorries.
  • Material supplied from QA source ensuring consistency of mixing and delivery temperature.
  • The use of chuted vehicles –allowing the hot material to be kept on the insulated lorry for as long as possible. These chutes are used to direct the asphalt accurately into the wheelbarrows so it can be quickly moved and deposited where the rake hand needs it.
  • Next comes the most important ingredient – a highly skilled, experienced and fully manned asphalt crew. A typical hand lay crew will consist of barrow-men, rake-hands, roller operator and finishers. Each has a pivotal role to play in producing a top quality surface. Teamwork is essential.
  • The temperature at which the material is laid is vital to the outcome of the operation, therefore rapid use of material is extremely important. Three or four men cannot do this, so you should find out about manning levels from your proposed contractor.
  • Rolling must commence as soon as the material is laid, with water constantly being applied to the roller drums in order to prevent the hot asphalt from sticking.
  • Twin drum vibratory rollers are essential.
  • Safety and team training is very important!

Step-by-step essentials for machine lay work

  • Material delivered on purpose built insulated delivery lorries.
  • Material supplied from QA source ensuring consistency of mixing and delivery temperature.
  • You will need the aid of a modern, high tech paving machine with an electrically heated screed to ensure the asphalt is laid to an accurate profile at the optimum temperature. Martin Cowman operate a fleet of Vogele pavers in a variety of sizes, all of which were renewed in 2014.
  • High performance compaction equipment and twin drum vibratory rollers to ensure thorough compaction.
  • The most important ingredient: an experienced, highly skilled asphalt gang. Two men and a dog cannot achieve high quality machine laid asphalt!
  • MCL operate machine crews of eight to ten men to ensure attention to detail. A typical machine crew will comprise a paver operator, two screw-men who control the screed, two rake-hands, two roller drivers and two finishers.
  • Material must be used promptly due to working constraints in relation to temperature. Compaction should commence as soon as material has been placed.

Whether or not a job is machine laid or hand laid there are a few principles that remain the same. In relation to the material thickness:

2.5 x Max Aggregate Size or

  • AC20 Binder (min 50mm thick)
  • A32 Basic (min 80mm thick)
  • AC10 Surf (min 25mm thick)

Below shows examples of typical layer thicknesses for different jobs. Obviously every job is different, but this gives you an idea of the components beneath the surface layer!

Calculations table Footpath (mm) Driveway (mm) Car park (mm) Road (mm)
Surface 20mm 25mm 30mm 30-40mm
Binder 50mm 60mm 70mm 60-70mm
Base N/A N/A N/A N/A
Sub-base 150mm 200mm 225mm 450+mm

Basic principles to remember

  • Must be laid hot.
  • Must be levelled/compacted immediately.
  • Post laying, it must be left to cool before use.
  • Surfaces are built up in 3 layers: base course, binder course, surface course.
  • If you want results you need a crew of experienced professionals along with the right equipment.

Steer clear of the Wild West!

Professional experienced asphalt contractors will deliver a quality product. The tools and skills used to lay asphalt are beyond the most passionate DIY enthusiast, it is best to leave it to the professionals on this one!

Make sure you get references if you have not used a contractor before. At Martin Cowman Limited all of our operatives are directly employed and fully trained to the appropriate industry standards. Equipment is regularly updated, serviced and tested. We pride ourselves on offering outstanding service and quality at competitive prices. Be very careful of “cowboys” who offer discounted prices. Expect a thin surface that offers minimum wear protection and will ultimately break up in a couple of months or in some cases weeks! (Not all of them look like this!)