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Typical roof costs breakdown (based on 400 m2 of roof)
COMPONENT COST (£)
Aluminium standing seam
Stucco embossed roof sheets 20/m2
Insulation 10/m2
Clips and thermal barrier 12/m2
Vapour control layer 7/m2
White polyester liner sheets 15/m2
SUBTOTAL64/m2
Overheads & profit @ 15% 10/m2
BASIC TOTAL 74/m2
Extra over costs (dependant on design):
Fall arrest system 65/m
Eaves closer excluding fascia 25/m
Hip closer 75/m
Ridge closer 35/m
Single-ply roof membrane  
50 mm asphalt in three coats including 30/m2
Separating layer 8/m2
120 mm insulation 27/m2
Vapour control layer 7/m2
SUBTOTAL72/m2
Overheads and profit @ 15% 11/m2
BASIC TOTAL 83/m2
Extra over costs:
Insurance backed guarantee cover 4%
Insurance inspection fee 750
Insurance tax 5%
Galvanized mild steel decking (if steel or timber roof structure) 18/m2
150 mm high turned-up skirting including angle fillet, expanded metal lathing, insulation and powder-coated aluminium flashing 40/m
600 × 600 × 50 mm precast concrete paving slabs 18
Slate roofing (35° pitch)  
Welsh slates 610 × 305 mm, 76 mm lap including tiling battens 78/m2
Counter battens (25 × 50 mm) 6/m2
Sheathing/ boarding (18 mm exterior quality softwood) 28/m2
Sarking/ underfelt 4/m2
SUBTOTAL116/m2
Overheads and profit @ 15% 17/m2
BASIC TOTAL 133/m2
Extra over costs:  
Double course at eaves 10/m
One-and-a-half width slates at verges including undercloak 18/m
One-and-a-half width slates at hips (both sides measured) 12/m
One-and-a-half width slates at valleys (both sides measured) 14/m
Typical roofing preliminary costs  
Project value Prelims (%)
Less than £50,000 20
Projects ranging from £50,000-100,000 17-20
Projects ranging from £100,000-250,000 15
Projects ranging from £250,000-500,000 12-15
Projects larger than £500,000 12