What flashings do
Wherever a roof meets something vertical, such as a chimney stack, a parapet, a gable wall or a dormer cheek, there is a joint that must be sealed against water. Lead flashing is the traditional solution. It is malleable, so it can be dressed to the shape of the junction, and it lasts well when properly installed.
How flashings fail
- Cracking from thermal movement where sheets are too large or fixed too rigidly
- Lifting or being pulled out by wind
- Failed mortar in the chase that holds the top edge
- Poor repairs with sealant or bitumen tape that have dried and split
- Theft of lead, which leaves the junction open
- Corrosion caused by contact with certain materials or poor detailing
Typical locations
We replace flashings at chimney stacks, party walls and gable abutments, dormer cheeks, bay window roofs, roof windows and lead-lined valleys. Many Victorian and Edwardian houses in Newcastle and Tynemouth have a mix of these junctions, and storm exposure on the coast means that weaknesses show up quickly.
How replacement is done
The old flashing is removed and the substrate checked for rot or damage. New lead is cut to a suitable code, or thickness, for the location, and installed with soakers, step flashings, aprons and cover flashings as appropriate. The upper edge is wedged into a raked joint and pointed, rather than relying on sealant. Fixings are limited so the lead can move, and length is kept within recognised limits. Following guidance from the Lead Sheet Association is normal good practice, and we work to those principles.
Why repairs with sealant fall short
Sealants and tapes can be a quick patch, but they dry out, crack and fail, often leading to bigger problems. A correctly detailed lead flashing usually outlasts them many times over.
Related work
Flashings are often renewed along with chimney stack restoration, parapet repairs, roof valley repairs and dormer repairs. Where leaks have been long-running, timber may need replacing, see roof timber strengthening.
Replacing flashings is usually a repair and does not need planning permission, but conservation area and listed building rules can apply. Check the Planning Portal.
Frequently asked questions
Why does my roof leak even though the tiles look fine?
Leaks often start at junctions such as chimneys and abutments, where flashings have failed. Tiles may be sound while the flashing is cracked or lifted, and water can travel some distance inside before showing.
Is lead the only choice for flashings?
It is the traditional choice and well suited to period buildings, though there are alternatives. We discuss what is appropriate for the building and its setting.
