SR structural roof decks provide a clean uncluttered soffit for the roofing system.

It is possible to enhance this uncluttered appearance by utilising the structural roof deck as a diaphragm to transfer wind loads from the perimeter walls to internal vertical bracing/walls, therefore reducing, or removing the need for in-plane roof bracing.

To design the deck as a diaphragm, the following must be considered:

• Implications of deck layout, void sizes/locations and vertical bracing/wall positions.
• Line loads applied to the diaphragm perimeter
• Fixings to all perimeter edges of roof deck area
• Minimum of three vertical bracing/braced wall locations required

It is important to note that fixing type and frequency may need to be changed to enable diaphragm design - Refer to Fig.8.13a for recommended standard fixing configurations.

For useful guidance on stressed skin diaphragm design, refer to:

• ECCS Publication No88: European Recommendations for the Application of Metal Sheeting acting as a Diaphragm
• BS 5950-9: Structural use of steelwork in building – Code of practice for stressed skin design
• SBI Document 174: Stabilisation by stressed skin diaphragm action
• BS EN 1993-1-3: Cold-formed thin gauge members and sheeting, clause 10.3