Lead flashing is one of the roofing details that most consistently produces defect claims in the two-year warranty period following handover. The mechanism is not complicated. Lead flashings that are installed incorrectly, or that are specified to insufficient standard, fail slowly. Water finds the failure. The internal finish shows the water. The claim arrives.
The specific failure modes are well known. Lead sheet weight too low for the exposure. Overlaps insufficient for the pitch. Fixings too widely spaced. Chase cuts not deep enough. Sealant used inappropriately as a substitute for correct dressing. Each is a specification and workmanship item, not a mystery. Each is preventable at design and installation stage.
The Lead Sheet Association's guidance sets out the standards. Code numbers indicate the sheet weight per square metre. Recommended overlaps are specified by pitch. Fixing patterns are defined for different exposures. Chase details are illustrated for different substrates. A roofer working to the LSA guidance produces flashings that hold up. A roofer improvising produces flashings that fail.
The most common areas where lead flashing appears on new build housing are chimneys, abutments where roof meets wall, valleys, dormer surrounds, and small roof-to-roof interfaces. Each has its own detailing requirements. Each is a discrete piece of work that either meets the LSA standard or does not.
For developers and QSs, the practical issue at tender stage is not usually the lead specification itself, which is often boilerplate in the contract documents. It is whether the installer has the trained personnel to deliver the detailing consistently. Lead work requires specific skills that not every roofer possesses. A contractor who sends generic roofing labour to fabricate chimney flashings produces a different outcome to a contractor who has trained leadworkers.
Globe Roofing's site teams include operatives with Lead Sheet Association leadworking qualifications. On plots where meaningful lead detailing is required, those qualified operatives are the ones fabricating the work. The install records show which operative did which flashing, and the LSA qualifications are on file.
That evidence trail matters for warranty defence. Where a defect claim is raised in year one or two of the warranty period on a lead flashing, the developer's position is materially better if the install records show a qualified leadworker fabricated the flashing to LSA standards using specified materials. Where the records are silent, the developer's position is weaker.
There is a related point about chase depth. UK new build brickwork often produces chase cuts that are cosmetically acceptable but structurally shallow. A lead flashing set into a shallow chase and sealed appears fine at handover but is not mechanically retained. Over the first winter of thermal movement, the flashing works loose. Water finds the joint.
Globe Roofing's chase specification requires the brickie gang or the roofing gang, depending on the sequence on the scheme, to cut chases to a specified depth before the flashing is installed. Where the chase is not to depth, it is cut deeper before the flashing goes in. This adds a small amount of time on site and prevents a defect that would otherwise emerge two years later.
For developers looking to reduce warranty period defect claims on new build housing, lead flashing detailing is one of the higher-leverage areas to focus. A small investment in specification clarity, competent installation and documented evidence prevents claims that are otherwise almost inevitable across a portfolio of comparable schemes.
Talk to Globe Roofing
To discuss lead flashing detailing on your scheme on your scheme, contact Globe Roofing on 01223 890727 or email enquiries@theglobegroup.co.uk.
