Lead flashing on a roof is lead used to seal the joints between surfaces on a roof. This can be between brickwork and tiles, or where tiles meet creating a valley or gully way. The leadwork is called flashing and the purpose of the flashing is to waterproof the roof. Originally flashing was on lead but nowadays there are lead-free alternatives to flashing. 

Common flashing areas are around;

• the base of a chimney
• the edging of a skylight
• a vent pipe protruding from the roof
• dorma windows
• the drip edge along Eaves
• any gully created on the roof from different pitches meeting

Is there lead free flashing?

Traditional flashing was made from lead, referred to as leadwork. A modern day alternative to leadwork is lead-free flashing. Roof flashing can be made from metals such as; copper, aluminium, stainless steel, or galvanised steel.

People are steering clear from leadwork because lead is toxic and harmful to the environment. Lead-free flashing is safe for the roofer to install and is suitable for water butts and other forms of rainwater harvesting.

Lead-free alternatives are often lighter than lead so less weight on the roof for the joists to handle.

​​A listed building or a historic building may be an instance where leadwork must be used, rather than a lead-free option, to preserve the building's authenticity.

Popular choices for UK roofs with lead-free flashing include;

Aluminium Flashing
Well priced, popular flashing as it can be used on many different types of roofs. Aluminium flashing can be bent and cut to fit any shape. The downside to aluminium flashing is that it does corrode easily.

Vinyl Flashing
This is a lightweight material that is more expensive than aluminium flashing. Although it is not suitable for colder, harsher weather, it is alright for rainy wet weather. Vinyl flashing is prone to cracking.

Steel Flashing
Steel flashing is zinc-coated and often used in the construction of roofs and chimneys. It is a longer lasting flashing that does not corrode as easily as aluminium flashing. 

Copper Flashing
Copper flashing is lightweight and resistant to cracking. Copper can withstand harsh climates but it is difficult to shape as needed along the roof. Copper flashing is used with a sealant that gives an additional barrier of waterproofing.

When does flashing need to be replaced?

The most obvious time to replace flashing and leadwork is when reroofing. If you are replacing your roof, existing flashing will be removed and new flashing (lead or lead-free) should be fitted. This is because old flashing may already have deteriorated faster than the roof and the old flashing may be damaged during the roof removal.

Otherwise, if you are not replacing the roof, but you have noticed the existing flashing is damaged or corroded, then the flashing will need to be replaced. A roofer will let you know after inspecting the roof, if it is a section of flashing needing replacing, if a section can be fixed, or worst case, if all of the flashing leadwork needs replacing. 

Visible signs that it may be time to replace the flashing is;

• signs of water ingress inside the loft or ceilings coming from the roof
• rust stains on the roof
• visible gaps in the caulking around the flashing
• mortar joints near the flashing disintegrating
• big gaps beginning around stone or brick
• cracks in mortar or the chimney is beginning to show signs of cracking

How much does replacing flashing and leadwork cost?

The costs involved in redoing flashing and leadwork depends on the size of the roof area needing the new flashing, what type of material was previously used and which material will be used for the new flashing, the condition of the roof and shingles, whether scaffolding is needed to access the roof and of course, labour time of the roofer installing the flashing and leadwork.

For a roofer to renew all four sides of chimney flashing, in total this could take the roofer a full day. Replacing the leadwork may only be 3 hours of time but setting the scaffolding and taking that down will be hours as well as removing the existing leadwork.

When it comes to a roofer needing to replace all of the flashing on a two bed detached house, labour time could run into 3 days of labour.

Cost to replace flashing and leadwork	Per	Average total labour cost
Replacing flashing on a 2 bed detached house	Per day	£650
Replacing flashing on a 2 bed terraced house	Per day	£540
Replacing chimney flashing	Per day	£180
Repairing a section of flashing	Per hour	£90

 

Can new flashing go over old flashing?

The roof should only have one set of flashing at a time. New flashing should not be layered over old flashing or leadwork as this may cause the flashing to be susceptible to water leaks.

Flashing can be installed on top of shingles but more often it is installed under the shingles. There are three types of flashing found on roofs;

Apron Flashing
Apron flashing or cover flashing is what is usually found on roofs where a roof meets the brickwork of a house or chimney. Apron Flashing is used on slate and tile roofs where they meet a wall, on conservatory roofs, and around bay windows.

Step Flashing
Step flashing allows a roof to meet where the roof is a lower height than wall it is meeting, perhaps due to a side return or extension. The name 'step flashing' is because of the pattern created in the lead by a series of cuts that visually looks like steps of a staircase. Doing the steps in the flashing means that the brickwork can remain un-cut which is aesthetically pleasing and better for waterproofing and to avoid corroding brickwork.

Chimney flashing
Chimney flashing is the flashing around the chimney to stop water from seeping through the roof at the base of the brickwork where the chimney meets the roof.

Replace or repair flashing?

If the leadwork or flashing has a small hole or there is a visibly corroded tiny section that seems to be allowing water to leak inside, instead of going to the expense of removing and replacing the whole section of flashing, a roofer would be able to patch the small hole.

Two ways of repairing the flashing is either;

using roofing cement to plug the corroded piece or small hole

or

using the same material as the flashing, the roofer can make a patch repair to the flashing.

Both these ways should only be done on small holes that are no more than 3/4 inch in diameter.

Estimates for common roofer jobs;

Rates for other trades