Accurate calculation of wind loads acting on roofs is crucial for design. SPRA members apply safety factors to the means of attachment (mechanical, adhesion, ballast) to ensure a wide margin of security. SPRA Technical Committee has appointed a task group to review the new calculation method EN1991-1-4 which is due to replace the existing (BS6399 Part 2) during 2010. The task group has taken a series of notional buildings in various UK locations and compared the wind loads calculated by these methods. A preliminary report is available here