Lead Hip and Ridge Rolls: Bossing vs Machine-Forming, Tack Fixing and Code Selection

Summary

Lead hip and ridge rolls are among the most visible elements of a quality leadwork installation — and among the most commonly done poorly. A well-formed lead roll over a hip or ridge will be smooth, evenly dressed, free of wrinkles, and will sit flat on the tile surface for its full length. Poor work shows as puckering at the sides, split seams at saddle pieces, lifting at tack positions, and cracking at the roll ends.

Hip and ridge rolls are not simply folded lead. They require the lead to be worked into a complex three-dimensional shape at each tile course junction. Where a hip meets a ridge, or where a hip meets a valley, a bossed junction saddle piece is required — a hand-formed piece that wraps around the intersection geometry without cutting or soldering. The craft skill involved in producing clean bossed saddle pieces takes significant practice and is one of the key differentiators between a competent leadworker and a general roofer attempting lead work.

Understanding the correct bay lengths for hip and ridge rolls is critical. Because hip and ridge rolls run up or along the slope, they experience the same thermal expansion forces as flat roof bays, but in a more constrained geometry — the roll is held down by tacks and is sitting on a relatively narrow board with tiles on both sides. Maximum bay lengths must be respected, and saddle pieces must be formed correctly to allow adjacent bays to move independently at their junction.

Key Facts

• Code 4 minimum — for all domestic hip and ridge rolls; 1.80mm thick, 20 kg/m²
• Code 5 — for exposed hips, chimneys with hip abuttments, high-rainfall regions, or complex hip geometry
• Maximum bay length (Code 4) — 1,500mm
• Maximum bay length (Code 5) — 1,500mm (same limit; heavier code adds durability, not longer bays)
• Tack fixing — Code 4 lead tacks or clips, nailed to hip/ridge board, at maximum 500mm centres
• Hip board — structural timber board nailed over hip rafter; provides substrate for lead and tiles
• Ridge board — structural timber running along roof apex; lead ridge roll laps both tile courses below
• Saddle piece — hand-bossed junction piece at hip/ridge intersection, valley/hip intersection
• Gusset piece — additional bossed insert at complex geometry junctions where a saddle piece alone is insufficient
• Roll width — lead must extend minimum 150mm either side of the hip/ridge centreline onto the tile surface
• Bossing — hand-forming technique using bossing mallet and bossing stick to stretch and work lead around compound curves
• Machine-forming — using a lead bender or hand bender tool to pre-form straight sections; not suitable for complex junctions
• Tack type — 25mm × 100mm Code 4 lead strip, folded and nailed with two galvanised or stainless wire nails
• Common failures — split along roll centreline (too long a bay, overtightened tacks); lifting at tack positions (tack too narrow or nail pulling out); cracking at saddle piece folds (insufficient bossing)
• LCA Manual — Lead Sheet Association Manual is the primary UK technical reference

Quick Reference Table

Detailed Guidance

Hip Roll Construction

A hip roll covers the external angle formed at the junction of two adjacent roof slopes. The hip rafter runs diagonally from eaves to ridge; a hip board (typically a 75mm × 50mm or 100mm × 50mm sawn softwood) is fixed over the hip rafter to provide a flat bearing for the lead and the hip tiles on either side.

The lead roll is cut to a width that gives a minimum 150mm cover on each tile face below the roll. The total sheet width is therefore approximately 300mm plus the width of the roll itself (the portion that wraps over the hip apex). For a typical 60mm-wide hip board, a sheet approximately 350–400mm wide is needed.

Forming the roll: the lead is centred over the hip board. The two side wings are dressed flat onto the tile surfaces on either side. The centre portion is folded upward to form a raised roll over the hip apex. The roll can be:

1. Machine-formed (hand bender): a lead bender or former tool is used to pre-form the roll profile on straight sections. Efficient for long, straight runs. The former is removed after forming.

2. Bossed (hand-formed): a bossing mallet and bossing stick are used to work the lead around the hip profile, particularly at changes of angle or at saddle pieces. Required at all junctions.

The finished roll should stand approximately 50mm above the tile surface at its apex to shed water effectively and to provide adequate material at the apex to resist splitting under foot traffic.

Ridge Roll Construction

A ridge roll covers the apex of a pitched roof, lapping over the top course of tiles on both sides of the ridge. Construction is similar to hip rolls: the lead is centred on the ridge board and dressed down each side to cover the top 150mm of the tile surface.

Ridge rolls are slightly simpler than hip rolls because the geometry is straight — there are no compound curves along the length of a straight ridge. However, the ends of the ridge roll require careful treatment:

• At the gable end: the roll is turned over the barge board and fixed; a lead saddle may be needed at the junction with any projecting chimney or wall
• At the ridge/hip junction: a bossed saddle piece is required to cover the point where the ridge transitions to the hip, since the geometry changes angle at this intersection

Ridge rolls are often neglected in maintenance. A ridge roll that has lifted or split along its centreline allows water to run directly into the roof void at the highest point of the roof — rainwater will travel a long distance before appearing as a damp patch inside.

Bossing vs Machine-Forming

Bossing is the traditional leadwork technique in which the lead is shaped by hand using:

• Bossing mallet — a wooden mallet with a large, slightly convex face used to stretch and compress the lead
• Bossing stick — a flat hardwood paddle used to smooth and work the lead against a backing form

Bossing stretches the lead at outer curves and compresses it at inner curves, allowing three-dimensional shapes (such as the corners of a back gutter or the junction of a hip and ridge) to be formed without cutting and soldering. A properly bossed piece has no splits, no wrinkles, and no thinning of the lead at the worked areas. Lead can be bossed up to approximately 300mm beyond its original flat length without splitting, giving considerable flexibility in forming complex shapes.

Bossing is the correct technique for:

• All saddle and gusset pieces at hip/ridge/valley junctions
• Dog-ear corners on flat roofs
• Back gutter corners
• Any compound curve that a bender tool cannot form

Machine-forming with a hand bender (a simple handheld roller or brake tool) is used for pre-forming the roll profile on straight sections of hip and ridge rolls. It is faster than bossing for straight runs and produces a consistent roll profile. However, machine-forming cannot produce the compound curves required at junctions — a machine-formed roll will split at the edges when forced around a three-dimensional corner.

On a complete hip roof:

• Straight hip sections: machine-formed acceptable
• Hip/ridge junction: must be bossed saddle piece
• Valley/hip junction: must be bossed saddle piece
• Hip at eaves: must be bossed or dressed by hand

A leadworker who only uses machine-forming and avoids bossing will produce joints that look acceptable on straight runs but will leak at every junction.

Tack Fixing Detail

Lead tacks are the only acceptable method of fixing hip and ridge rolls to the substrate. Direct nailing or screwing through the lead is not acceptable — it would create a rigid point that prevents thermal expansion and will cause cracking around the fixing hole within a few cycles.

A tack is formed from a strip of Code 4 lead approximately 25mm wide × 100mm long, folded in half to give a 25mm × 50mm double-thickness strip. Two galvanised or stainless steel wire nails (50mm minimum length) are driven through the fold and into the hip or ridge board. The protruding tongue of the tack then laps over the edge of the roll lead, holding it down without clamping it.

Tacks are placed at maximum 500mm centres. Each tack is positioned on one side of the roll only — alternating sides is acceptable. The tack must not be bent so tightly over the lead that it prevents the lead from sliding longitudinally; there should be a small amount of play in each tack once fitted.

At the joints between bays (at saddle pieces), tacks should be placed within 50mm of each side of the joint to prevent the lead ends from lifting.

Saddle and Gusset Pieces

At all junctions on a hip or ridge roll system, a saddle piece is required. This is a separate bossed piece that covers the joint between two adjacent roll bays and wraps around the geometric change at the junction.

Ridge/hip junction saddle: covers the point where the ridge roll ends and the hip roll begins. This junction involves a change of angle in two planes simultaneously. The saddle must be bossed to cover both sides of the junction, lapping over the last bay of the ridge roll and the first bay of the hip roll by a minimum of 75mm on each side.

Hip/valley junction saddle: where a hip meets a valley (as occurs on complex roof forms), a more complex gusset piece is required. The geometry at this point involves three roof planes meeting, and the lead must be bossed to cover the exposed angle between all three. This piece is often the most technically demanding element of a hip roll installation.

Chimney/hip junction: where a hip rafter runs to a chimney, the lead hip roll must be coordinated with the step-and-cover flashings on the chimney face. The final bay of the hip roll is dressed up behind the cover flashing on the chimney side and the cover flashing is carried over the top of the hip roll end. A gusset piece bossed into the internal corner between the hip roll and the chimney flashing is required on exposed elevations.

Common Failures and Diagnosis

Split along roll centreline: The most common hip roll failure. A longitudinal crack running along the apex of the roll for most of the bay length. Cause: bay too long (exceeds 1,500mm), or tacks fixed too rigidly at both ends. The lead has been placed in tension along its length as it tries to expand but is constrained. Remedy: strip and relay in correctly sized bays with free-movement tacks.

Lifting at mid-bay: The roll has peeled away from the tile surface in the centre, sitting proud in a tent-like profile. Cause: bays too long and no tacks at mid-bay, or tacks pulling out of rotted board. Remedy: check board condition, add mid-bay tack, or relay if board is rotten.

Cracking at saddle pieces: Fine cracks at the bossed folds of a saddle piece. Cause: insufficient bossing (the lead at the fold was worked too sharply without enough stretching, creating a stress concentration); or the saddle piece was cut too small and forced to cover more geometry than its mass could accommodate. Remedy: replace saddle piece with a correctly sized and properly bossed piece.

Water under roll: Where tiles on either side of the roll are pitched steeply and wind-driven rain is significant, water can work its way under the edge of the roll. Cause: roll width insufficient (less than 150mm onto the tile surface). Remedy: replace with wider lead or add a bossed edge flap dressed flat onto the tile.

Frequently Asked Questions

Can I re-use old saddle pieces when relaying hip rolls?

No. Old saddle pieces that have been in service for decades will have significant work-hardening at their bossed folds. Even if they appear intact, relaying will require re-bossing them slightly to fit the new bay positions — and work-hardened lead will crack when re-worked. Always use new Code 4 lead for saddle and gusset pieces. The cost of the additional lead is negligible compared to the cost of a callback for a leaking saddle.

Do hip rolls need to be dressed under the ridge roll or can they butt up to it?

The top of the hip roll must be covered by the ridge roll saddle piece or by the last course of the ridge roll itself, lapping a minimum 75mm over the hip roll end. A hip roll that simply butts against the ridge with no lap will allow water ingress at the junction. The correct detail is for the ridge roll or its saddle piece to be the topmost element, overlapping the hip roll end.

What is the hip board spec — does it need to be a specific size?

The hip board must be wide enough to provide full bearing for both the lead roll and the hip tile on each side. A minimum 75mm wide × 50mm deep (finished) softwood board is typical for standard concrete or clay plain tiles. For large-format interlocking tiles, a wider board (100mm) may be needed. The board must be pressure-treated with preservative (Use Class 3 minimum) and securely nailed to the hip rafter at maximum 400mm centres.

Is solder or welding ever used on hip or ridge rolls?

Neither soft solder nor lead welding is used on hip or ridge rolls in standard domestic work. All junctions are achieved by mechanical lapping with correctly bossed saddle pieces. Welded or soldered joints on lead rolls in an exposed position will fail from thermal cycling much faster than a correctly formed mechanical joint.

How do I price a hip roll replacement versus a ridge roll replacement?

Hip rolls are significantly more labour-intensive than ridge rolls of equivalent length because of the diagonal geometry (which means more cutting and waste), the requirement for bossed junction pieces at top and bottom, and the physical awkwardness of working along a diagonal slope. As a rule of thumb, a hip roll replacement takes approximately 40–50% longer per linear metre than a straight ridge roll replacement. Ensure your quote reflects the number of hip/ridge/valley junctions — each bossed saddle piece adds approximately 30–45 minutes to the installation time.

Regulations & Standards

• Lead Sheet Association (LSA) Manual — Specifies Code 4 minimum, maximum bay lengths, tack fixing methods, and saddle piece requirements for hip and ridge rolls

• BS EN 12588 — Specification for rolled lead sheet for building purposes; defines all code thicknesses

• BS 5534:2014+A2:2018 (Slating and tiling for pitched roofs and vertical cladding — Code of practice) — Includes requirements for fixings and junctions at hips and ridges; references lead flashing details

• Building Regulations Approved Document C — Resistance to moisture; hip and ridge junctions must be weathertight

• Lead Sheet Association — Rolled Lead Sheet: The Complete Manual — Primary technical reference for hip and ridge roll details, bay lengths, and bossing guidance

• BS 5534:2014+A2:2018 — Slating and tiling code of practice; fixing and junction details at hips and ridges

• BS EN 12588 — Rolled lead sheet specification

• lead thermal expansion provision — Why 1,500mm bay limits matter; expansion coefficients and fatigue failure explained

• lead chimney flashings — Step-and-cover flashings that coordinate with hip rolls at chimney junctions

• lead flat roof coverings — Bossing technique used in dog-ear corners; roll construction principles