Bituminous layers

Tables 35 a, b and c provide:

  • the required minimum design thicknesses; and 
  • the options for flexible and modular (block) materials that should be used for different development road types.

Roads not covered by this table should be designed on a site-by-site basis to the Design Manual for Roads and Bridges (DMRB), such roads include; the primary route network, classified roads, all-purpose roads, and bypass/distributor roads.  

Where it is necessary to alter or improve an existing road to serve a development, in all cases the minimum depth of surface course, binder course and base layer should not be less than that of the site access road, as given in Table 35. For example, if a road is being widened to serve a housing development accessed by a 'residential access road', then the material depth should not be less than 250mm - equal to 40mm+60mm +150mm. It may be necessary to overlay or reconstruct the existing carriageway to achieve the required depth.

Table 35(a): Road carriageway construction depths - Major Residential Access Roads (Primary Streets) and Residential Access Roads (Secondary & Local Streets)
  Bituminous Notes Block
Surface course

40mm

SMA 10 surf 40/60

(Appendix 7/1 Material Ref. SC2)

1, 2, 3

80mm

40mm

HRA 55/10 F surf 40/60 des

(Appendix 7/1 Material Ref. SC7)

1, 2, 3

80mm

40mm

AC 10 close surf 100/150

(Appendix 7/1 Material Ref. SC11)

1, 2, 3

80mm

Binder course

60mm

AC 20 dense bin 100/150 rec
(Appendix 7/1)

4

30mm sand
60mm AC 20 dense bin 100/150 rec
(Appendix 7/1 )

Base

150mm

AC 32 dense base 40/60 rec
(Appendix 7/1)

 

100mm AC 32 dense base 40/60 rec

(Appendix 7/1)

Table 35(b): Road carriageway construction depths - Shared Surface Residential Accesses (Tertiary Streets)
  Notes Block
Surface course

1,2,3

80mm

Binder course

4

30mm sand

Base  

110mm AC 20 dense bin 40/60 rec
(Appendix 7/1)

Table 35(c): Road carriageway construction depths - Industrial access roads
  Bituminous Notes Block
Surface course 50mm

HRA 35/14 F surf 40/60 des (14/20mm pre-coated chippings)

(Appendix 7/1 Material Ref. SC6)

1

Not permitted

Binder course 60mm

AC 20 dense bin 40/60 rec
(Appendix 7/1)

4

Not permitted

60mm

AC 20 HDM bin 40/60 des
(Appendix 7/1 Material Ref. BC4)

4

Not permitted

Base 190mm

AC 32 dense base 40/60 rec
(Appendix 7/1)

5

Not permitted

190mm

AC 32 HDM base 40/60 des
(Appendix 7/1 Material Ref. B4)

5

Not permitted

Table notes
Note number Explanation 
1 Polished stone values (PSV) of course aggregate in surface course materials shall be determined from ‘Table 1.1 Polished Stone Values for carriageway resurfacing treatments’ in the council’s ‘Carriageway - Skidding Resistance Procedure
2 Laid to agreed material and correct gradients.
3 Refer to the surfacing ‘Materials Palettes document for further guidance on the use of surface course materials
4 Any binder course material laid as a running surface course prior to the final surface course being laid must have a minimum PSV of 55 and an aggregate abrasion value (AAV) of 7. This includes under block paved surfaces in carriageways.

Key:

HRA = Hot Rolled Asphalt;

AC = Asphalt Concrete;

SMA = Stone Mastic Asphalt

Full details of the permitted standard materials can be found in Appendix 7/1 of the council’s Specification and the Materials Palettes document.

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