Specialist cost update: Envelope | Features

Curtain walling - Lead times and costs
Typical design options	Approximate costs
Cost of each additional frit	£17-25/m2
Extra cost for faceting	10-15%
Extra cost for single radius	60% minimum
Glass external fins, depending on profile	£280-400/m
Aluminium external fins, depending on profile	£110-225/m
Extra cost of laminated glass in place of toughened	£17-25m2
Inter-cavity blinds (motorised tilt only, manual raise and lower)	£60-70/m2
Additional layer of glazing (opening inwards for access to cavity)	£100-135/m2
Miscellaneous items
Parapets	£280-450/m
Penetrations through system	£1,650-2,000 each
Single doors	£4,000 each
Double doors	£6,500 each
External soffits	£450/m2
Interface with other elements, e.g. stone	£280/m
Secondary steelwork	Project specific

Roofing - Typical roof prices
Single-ply membrane	£90-105/m2
Natural slate	£140-180/m2
Aluminium standing seam	£80-100/m2
Two-coat asphalt	£140-180/m2
High-performance bitumen felt	£80-100/m2
Stainless steel standing seam	£100-130/m2
Clay tiles	£60-80/m2
The quality, procurement route, timescales, complexity of design and desire of contractors to tender should be carefully considered in project-specific estimates and their outturn cost.
* UK Roofing Materials Marketing and Development Report 2007 (£600 from MBD, www.mbd.co.uk)

Stone construction and restoration - Budget costs
Washing dependent on method	£4.95-11.00/m
Controlled air abrasion	£12.10-20.90/m
Poultices	£33-110/m
Chemical cleaning	£7.15-14.30/m