Lead Flashing in Windermere

The Problem

This substantial four-bedroom detached house is built of local Lakeland stone with a Westmorland slate roof, typical of the finer residential properties around Windermere. Over the years, the property had been extended twice — once in the 1960s with a single-storey kitchen extension, and again in the 1990s with a two-storey side addition. Each extension created new wall-to-roof junctions, and the lead flashings at these junctions had been installed to varying standards. The 1960s kitchen extension had Code 3 lead flashings that had corroded through along the fold lines, while the 1990s extension had been flashed with a lead substitute material that had become brittle and cracked. The original Victorian section had lead flashings at the chimney and a rear abutment wall that, while better quality, had developed fatigue cracks after well over a century of service. The cumulative effect was water ingress at five separate locations around the property — two bedrooms, the kitchen ceiling, a utility room wall, and the chimney breast in the sitting room. The homeowner had spent years applying mastic patches and sealant, each lasting only a season before the leaks returned.

Our Solution

We carried out a comprehensive survey of every wall-to-roof junction on the property and produced a detailed specification for complete lead flashing renewal throughout. Working from scaffold and roof ladders, we systematically stripped all existing flashings and substitute materials back to bare masonry. Each junction was then assessed for its specific requirements — chimney flashings were formed from Code 4 lead to BS EN 12588, while the more demanding abutment flashings and the chimney back gutter were specified in Code 5 for additional durability. Every step flashing was let into freshly raked mortar joints to a depth of 25mm, wedged with lead clips, and pointed over with a lime-based mortar. Cover flashings were secured with lead wedges and sealed with lead mastic. The kitchen extension abutment received a continuous lead apron flashing dressed over a tilting fillet, with a generous 150mm upstand against the stone wall. We also renewed the lead soakers beneath every slate course at all abutment positions, ensuring a fully weathertight junction even under wind-driven rain conditions. Where the 1990s extension met the original building, a particularly complex junction required a bespoke lead detail incorporating both step and cover flashings with a lead-lined secret gutter to manage water flow at the intersection.

The Result

For the first time in years, the homeowner can watch heavy rain from the comfort of a completely dry house. All five leak locations have been permanently resolved, and the consistent use of Code 4 and Code 5 lead throughout means these flashings will outlast the current owners by generations. The traditional leadwork detailing is sympathetic to the Lakeland stone character of the property — dressed neatly into the stonework rather than surface-fixed with clips and adhesives. The complex junction where the extensions meet the original building has been particularly satisfying to resolve, as this was the leak that no previous contractor had managed to stop. This project demonstrates the value of a comprehensive approach to lead flashing work rather than piecemeal patches — a philosophy we apply to every project across the Windermere area.

Code 4 Milled Lead Sheet

Code 4 lead (1.8mm thick) was used for all standard step flashings and soakers throughout this Windermere property. Milled to BS EN 12588, it provides the optimum balance of workability and durability for flashings that need to be dressed into irregular Lakeland stonework. Each piece was cut on site and hand-bossed to follow the contours of the random rubble masonry, a skill-intensive process that produces far superior results compared to machine-folded flashings. Code 4 lead has an expected lifespan exceeding 100 years in this semi-sheltered Lakeland position.

Code 5 Milled Lead Sheet

The heavier Code 5 (2.24mm) was specified for the kitchen extension apron, the chimney back gutter, and the bespoke junction detail — all positions where the lead is subject to greater water flow, thermal stress, or physical loading. The additional 25% thickness compared to Code 4 provides proportionally greater resistance to thermal fatigue cracking, which is the primary failure mechanism in lead flashings. On long, uninterrupted runs like the kitchen apron, Code 5 is essential to prevent the creep and buckling that can affect thinner grades.

Lead Wedges and Clips

All flashings were secured into mortar joints using traditional lead wedges — small folded pieces of scrap lead tapped into the joint to hold the flashing in position before pointing. This method provides a secure fixing that accommodates thermal movement without the stress concentrations created by mechanical screws or masonry pins. At exposed positions, additional lead clips were used to secure flashing edges against wind uplift.

Lead Patination Oil

Freshly installed lead has a bright silver appearance that takes 6-12 months to weather naturally to the familiar grey patina. Lead patination oil accelerates this process to just a few weeks, which is important both aesthetically — particularly on a prominent Windermere property — and practically, as the patina layer protects the lead surface from white carbonate staining that can mark adjacent stonework.