Costed: External works & drainage

AECOM’s David Holmes looks at external works and drainage costs

Pedestrian and vehicular access areas can be provided by many different materials. Popular choices include block paving and brick paviors, particularly for residential developments. Concrete paving stones can be a cost-effective alternative to traditional clay block pavers, especially if large numbers are required.
In industrial environments reinforced concrete is preferred for access roads and loading bays. These are often combined with brick paviors for turning areas which suffer the most wear and can be more easily repaired. Tarmac can be used for large areas, such as car parks, as it accommodates small settlements without detriment and can be used quickly after laying.
Street furniture is probably the largest and most diverse category of external works. Benches, seats and associated products are made in a wide range of material and styles.
The term ‘external works’ describes any works carried out to the external environment of a building project. These can provide functional and aesthetic features.
BRE’s description is: ‘All items outside the building footprint but inside the site boundary, encompassing wastewater and surface water drains, supply of utilities (eg gas, electricity and cabled services), footpaths, and access for vehicles including car parks and hard standings to be found in the vicinity of buildings.

Rates are a guide and current as at Q2 2016, based to a location of UK mean. No allowance is made for sundry or related preliminaries costs. VAT is excluded.


Housing cost models meeting minimum planning requirements or to maximise sales potential at economic cost. Soft landscaped space only; planting: turf ratio’s as shown; planting sizes and densities as indicated; 1 tree of 18-20cm girth at 1 tree per 100m2 overall external area; mulch and watering after planting

Landscape:turf and trees only; imported topsoil to turf at 50 thick      £1127-£1281/100m²
70:30 turf to planted area with imported topsoil to turf at 50 thick     £2145-£2437/100m²
50:50 turf to planted area; imported topsoil to turf areas at 50 thick     £2475-£2812/100m²


More dense landscape incorporating relaxation areas and larger planting schemes; generally more mature at implementation, with larger trees. Schemes often incorporate larger swathes of groundcover to give graded views over landscaped areas; planting density and sizes are of higher standard than housing. Soft landscaped space only. Planting:turf ratios as shown; sizes and densities as follows; 1 tree of 25-30cm girth at 1 tree/100m² overall external area; mulch and watering after planting

Landscape: turf and trees only; imported topsoil to turf at 50 thick      £1375-£1562/100m²
70:30 turf to planted area with imported topsoil to turf at 50 thick    £2365-£2687/100m²
50:50 turf to planted area; imported topsoil to turf at 50 thick    £2722-£3093/100m²


Civic and public areas in current climate encompass high quality surfaces for public access, larger planting and a need for furniture and lighting
Civic town centre area of paved open space; model area 500 m2
General open area; one 30-35cm tree with root cell planting system every 400m²; metal tree grid; one bench per 200m² and one bin per 500m²; granite kerb

Concrete slab paved     £10,120-£11,500/100m²
Granite paved      £17,600-£20,000/100m²
As above w/stepped terraces: 3no steps 10m long in 500m2 area    £20,900-£23,750/100m²

Living wall; design and installation of planted modules with automatic irrigation, fabric based systems; indicative area rates as shown:
Wall up to 20m²    £682-£775/m²
Wall up to 50m²    £539-£613/m²
Wall up to 100m²    £506-£575/m²
Wall up to150 m²     £495-£563/m²


Parking; macadam base and wearing course    £900-£1100/per bay
Parking; block paviors 80mm thick    £78-£90/m²
Pedestrian areas; 100mm thick concrete    £60-£70/m²
Modular grass concrete paving 100mm thick    £65 -£75/m²
Resin bonded 1mm-3mm golden pea aggregate pathways    £77-£90/m²

Access chambers
Excavate inspection chamber; concrete base; half section pipework and benching
Precast concrete inspection chamber 600 × 400 × 900mm deep    £479-£544

Polypropylene inspection chamber

Mini access chamber 600mm deep    £330-£375
475mm dia × 900mm deep; ductile iron cover with screw-down lid    £572-£650

Drainage pipe

Excavate and lay 100mm diameter upvc pipes › 1.0 m deep    £43-£54/m
Excavate and lay 150mm diameter clay pipes › 1.5 m deep    £85-£110/m
Excavate and lay 300mm diameter concrete pipes › 2.5 m deep    £150-£185/m
Excavate and lay 150mm diameter cast iron pipes › 1.5 m deep    £155-£200/m

Street furniture

Road signs; reflective traffic signs 0.25m² area on steel post    £115-£140
Road signs; internally illuminated traffic signs; dependent on area    £190-£225
Pedestrian area lighting, estate roads; 4-6m columns: 70W lamps    £215-£260
Main road lighting; 12-15m columns: 400W high pres sodium lamps    £580-£700
Benches; hardwood and precast concrete    £950-£1150
Litter bins; bolted to ground
precast concrete / hardwood slatted    £170-£215
cast iron    £350-£425
large aluminium    £520-£630
Planters: supply and install precast concrete planters w/exposed aggregate finish, topsoil, 50mm shingle and drainage mat
with assorted 5 litre and 3 litre shrubs to provide instant effect; 700mm dia × 470mm high    £836-£950/each