The Property

Roll Top Lead Bay Roof Detail

This project involved the installation of a traditional roll top lead bay to a period-style brick property. The bay sits beneath upper-level window openings and forms an important architectural feature to the elevation, requiring a finish that was both practical and visually sympathetic.

Lead bay roofs are relatively small areas, but they are highly exposed and technically important. They protect the structure below from rainwater, shed water away from the building and contribute significantly to the appearance of the facade.

The completed detail included roll top bay divisions, dressed lead panels, perimeter flashings, formed drips and carefully detailed junctions against the brickwork and window area.

What Is a Roll Top Lead Bay?

A roll top lead bay is a traditional lead roof detail where timber rolls are used to divide the lead covering into separate bays. The lead is then dressed over the rolls to form raised seams, creating the distinctive roll-top appearance.

The roll detail is not only decorative. It helps divide the lead into manageable sections and allows the covering to accommodate natural thermal movement. This reduces the risk of splitting, distortion and movement-related fatigue over time.

Leadwork Standards and Technical Approach

This project was completed using a standards-led approach focused on correct lead detailing, movement allowance and durable weathering performance.

• BS 6915 informed the design and installation of the fully supported lead sheet covering.
• BS EN 12588 governed the rolled lead sheet material specification.
• Lead Sheet Association guidance informed bay sizing, timber roll formation, fixing principles, bossing, dressing and general good practice.

The key principle on a roll top bay is that the lead must be able to move naturally while remaining securely weathered. This requires correct roll spacing, appropriate fixing, careful dressing and well-formed junctions at the perimeter.

Specification of Works

Preparation and Removal

• Safe access established to the bay roof area.
• Protection applied to surrounding glazing, brickwork and decorative features.
• Existing defective coverings and flashings removed where required.
• Bay structure inspected for support, falls and general condition.
• Area prepared for new substrate and leadwork installation.

Substrate and Support

• New 18mm exterior-grade plywood decking installed where required to provide a continuous support.
• Lead underlay / building paper laid beneath the lead sheet.
• Timber rolls formed to create the traditional roll top bay divisions.
• Perimeter edges, drips and upstands prepared to suit the bay geometry.

Leadwork Installation

• New coverings formed in Code 5 rolled lead sheet.
• Lead bays set out to suit the size, shape and appearance of the roof.
• Lead dressed neatly over timber roll details.
• Front edge formed to provide a clean and durable drip detail.
• Side edges dressed and weathered into the adjoining structure.
• Copper clips and fixings used where required to secure the lead without restricting movement.
• Lead flashings integrated neatly against the brick wall and window area.
• Corners bossed, dressed or welded where required to complete the weathering detail.

Finishing and Protection

• Patination oil applied to all exposed lead immediately after completion.
• Surrounding surfaces cleaned down.
• Completed detail checked for finish, continuity and weathering performance.

The Materials

This project used a traditional set of leadwork materials, each chosen to support the roll top bay detail and allow the lead to perform correctly over time.

• Code 5 lead
• Copper clips and fixings
• Exterior-grade plywood decking
• Building paper / lead underlay
• Timber rolls
• Patination oil

If you are trying to understand which code of lead is right for a similar detail, our shoppable lead chart is a useful starting point. For broader product learning, see The Lead Handbook and our lead roofing guides.