Mechanical Fixing of Bituminous Membranes on Upstands

Code of Practice BS8217:2005 requires Reinforced Bitumen Membrane capping sheets applied to slopes greater than 5° to be mechanically fixed to prevent membrane slippage.

Bauder specifications have historically covered this requirement for sloping roofs. However, BS8217 provides limited guidance regarding vertical upstands, when an upstand ceases to be part of the roof and becomes a wall, and for upstands above 250mm in height.

To provide clarity, the guidance below has been produced outlining Bauder's recommended fixing methods and fixing patterns for upstands.

Upstand Insulation

Where insulation is being used on an upstand, Bauder will specify a coating of Activator-Primer applied to the surface of the insulation (all insulation types) prior to installation of the self-adhesive underlayer.

This ensures sufficient adhesion between the insulation and underlayer and eliminates the requirement to mechanically fix through the underlayer prior to installation of the capping sheet.

Fixing of Insulation on Insulated Upstands Up to but Less Than 600mm

Insulation should either be bonded using PU Insulation Adhesive or mechanically fixed. Please refer to the project-specific Bauder specification for the required fixing method.

Regardless of the fixing method used, Bauder recommends:

• BauderROCK: One fixing positioned centrally within the board to retain it in place.

Fasteners for Insulated Upstands Exceeding 600mm

Use thermally broken tube washers with a minimum 45mm diameter round head together with suitable fasteners.

Tube size and fastener type should be selected in accordance with the recommendations of the fixing manufacturer. Fasteners should be installed through into the underlying substrate, ensuring the washer is pulled tight against the insulation.

• BauderPIR FA-TE: Five fixings per board, one in each corner and one centrally positioned.
• BauderROCK: One fixing positioned centrally within the board.

Capping Sheets

Terminating the Capping Sheet on the Vertical

To terminate the capping sheet on the vertical face, Bauder will specify the use of a Bauder aluminium peel bar together with appropriate fixings (to suit the substrate) installed at 150mm centres.

Where the capping sheet is terminated on the vertical, the peel bar must be covered with the specified flashing material dressed over the top to maintain waterproofing integrity.

Where a traditional lead cover flashing is used, a separating tape must be installed between the aluminium peel bar and the lead flashing.

A Bauder termination bar must not be used in this situation unless specifically detailed by Bauder.

Mechanically Restraining the Capping Sheet on the Horizontal

Where the capping sheet is taken horizontally across the top of a parapet, Bauder will specify either a Bauder aluminium peel bar (fixed at 150mm centres) or screws and washers with suitable fixings to suit the substrate.

Cap Sheet Cover Flashing

A separate flashing piece of capping sheet is required to cover the mechanical fixings.

Important Notes

For upstands utilising self-adhesive membranes only, mechanical restraint at the top leading edge of the capping sheet is required regardless of upstand height.

This applies to System Airtech installations and all areas designated as Torch-Free zones.

Please refer to the fixing tables and detail drawings contained within the original Contractor Update for project-specific fixing guidance.

Upstands Exceeding Approximately 1100mm

Bauder does not advocate the use of bitumen waterproofing systems on upstands exceeding approximately 1100mm in height due to fire regulation considerations.

Alternative waterproofing solutions should be adopted as specified by the project client.

Building Control should be consulted to confirm waterproofing requirements where upstands exceed 1100mm.

Mansard Roofs

Where a roof slope exceeds 70°, the area is no longer considered an upstand and should instead be treated as a wall.

This includes dormer side panels and similar constructions.

Bauder does not recommend the use of bitumen membranes in these situations due to fire regulation considerations. Appropriate alternative systems should be specified by the client or project designer.

Building Control may impose further restrictions depending on the project circumstances.

Guidance Tables & Standard Details

The original Contractor Update includes:

• Guidance table confirming fixing requirements for insulated upstands.
• Guidance table confirming fixing requirements for uninsulated upstands.
• Standard details for fixing on the horizontal.
• Standard details for fixing on the vertical (Torch-Free applications).

Situations not covered by these standard details may occur on site and Bauder may have project-specific details available for these scenarios.

In these instances, please contact Bauder Ltd for further guidance.

Please do not hesitate to contact me should you have any questions regarding the above.