The Property

Curved Lead Bay Window Restoration – Meadowhead, Sheffield

166 Meadowhead in Sheffield is a traditional late Victorian or early Edwardian semi-detached house. It is built in solid masonry with natural stone elevations typical of the region. The property features a pitched slate roof, along with some modern additions such as rooflights. However, it still retains key period details, including a prominent two-storey bay window with decorative features. Overall, the building reflects a durable family home with strong traditional character, set slightly elevated behind a boundary hedge.

The property includes a lead-covered bay roof. Although this is a small area, it is both highly visible and technically important. It sits directly below the window frame and is exposed to concentrated rainwater. As a result, these details often fail when the lead has been over-fixed, poorly detailed, or installed over a failing substrate. In addition, the bay roof plays a key role in the appearance of the front elevation.

For this reason, the work was not treated as a simple repair. Instead, the bay was fully stripped back, re-decked, and re-covered using Code 5 rolled lead sheet. The installation included correct underlay, copper clips, formed drips, and traditional detailing in line with recognised leadwork guidance.

Why the Original Leadwork Needed Replacing

In many cases, lead bay roofs fail because thermal movement has been restricted. This is often caused by over-fixing or incorrectly sized bays, which leads to splits and fatigue cracking over time. In addition, welded joints and corners are common weak points. Failure can also occur when the timber substrate beneath has deteriorated or become uneven.

Typical signs include visible cracking, lifted joints, and water ingress around the bay window. You may also notice staining or discolouration on the lead surface. In more advanced cases, the bay top can appear uneven or start to sag, indicating structural issues below.

Leadwork Standards and Technical Approach

This project was completed using a standards-led approach focused on proper lead detailing, correct material selection and durable support beneath the finished covering.

• 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, fixing principles, bossing, welting, corner formation and general good practice.

The bay roof should be replaced in line with BS 6915, BS EN 12588, and LSA guidance, starting with a new fully supported timber deck and underlay. New Code 5 lead is then installed in correctly sized bays, fixed with clips to allow for thermal movement, and formed with bossed corners, welded joints, and proper upstands and drip details to ensure a durable, watertight finish.

Specification of Works

Preparation and Removal

• Assess the structure of the bay window roof, taking accurate measurements of eaves lengths, ridge heights, and roof angles
• Carefully strip back and remove existing leadwork, flashings, and any associated coverings without damaging surrounding masonry or joinery
• Expose and inspect the timber substrate beneath, removing any decayed or inadequate decking and clearing all debris and fixings
• Prepare the area for replacement, ensuring the bay top is fully accessible and ready for new lead to be installed over all edges for a continuous, watertight seal

Substrate and Support

• Ensure the timber substrate is clean, dry and structurally sound, replacing any decayed or uneven sections to provide a stable base
• Install a suitable building paper over the deck to prevent moisture transfer and allow ventilation beneath the lead
• Form a fully supported deck, typically using exterior-grade plywood, securely fixed to provide continuous support in line with BS 6915
• Check that the structure beneath is rigid and adequately supported, ensuring it can carry the weight of the lead and allow for correct fixing and long-term performance

Leadwork Installation

• Install Code 5 lead base flashings at all abutments, dressed into the masonry with correct laps to form a watertight junction
• Set out lead bays to comply with BS 6915 and LSA bay size guidance, allowing for thermal movement across the bay window top
• Cut lead sheets to size and boss into shape to suit the faceted bay geometry without stressing the material
• Lay lead from the eaves upwards, forming bays with minimum 100mm laps to shed water effectively
• Fix lead using clips (not direct nailing across the sheet) to allow for expansion and contraction
• Form welted joints or welded seams where required, ensuring strength and watertight integrity at junctions
• Dress the lead neatly into corners, upstands, and around edges, forming a front drip detail to throw water clear of the structure
• Check all detailing, joints, and finishes to ensure a durable, watertight installation in line with BS EN 12588 and LSA guidance

Finishing and Protection

• Dress and finish the lead neatly, ensuring all edges, laps, and joints are smooth, secure, and fully watertight
• Apply patination oil and complete all sealing at abutments and edges to protect the lead and promote even weathering
• Carry out a final inspection to check joints, drainage, and detailing, ensuring the installation is fully compliant and free from defects

The Materials

This project used a straightforward but important group of materials, each chosen for a clear purpose within the bay roof build-up.

• Code 5 lead
• Copper ringshank nails
• 50mm copper fixing strip
• Building paper / lead underlay
• Lead sealant
• 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.