Lead Flashing

Lead flashings are strips of lead used to cover the gaps in roofs. They are an integral part of the roof, providing sealant qualities preventing water ingress. Flashings can vary in thickness depending on the weather conditions, other materials such as aluminium, copper, stainless steel and zinc alloy are sometimes used. Lead flashings minimise water ingress at connection joints such as vents, chimneys, and roofs to walls and windows and doors. Roof flashing is crucial to ensure the integrity of your roofs, without flashing it would almost certainly develop leaks and or mould. 

Areas you may find lead flashing

Flashings are generally used at the junction of two surfaces. Due to its flexibility, the lead flashings can be reshaped around most surfaces. The most common area flashing is used is along the edges of a chimney stack. It is placed around the junction where the chimney joins with the roof this prevents water ingress through the gaps. Other areas you may find lead flashing;

Roof to wall Flashing is used at the junction where the vertical part of the wall meets with the roof. It prevents water from seeping into the joints.

Drip edge flashing is used along the edges of the roof, it helps direct water into the gutters.

Lead flashing can also be used at the junction where two roofs meet. The flashing will divert the water away from areas susceptible to leaks.

Skylights, vents, pipes and other penetrations points are susceptible to leaks. The lead flashing is used around these areas to create a tight fit and prevent water ingress. 

Common Lead flashing defects to look out for

Although defects in lead flashing may be slow to show they can become damaged by the following;

  • Weathering and general old age.
  • Membrane shrinkage
  • Condensation.
  • If it is laid in a way that does not let the metal expand and contract.
  • Debris piercing the flashing. 
  • Puddles 
  • Inadequate overlaps of joints.

It is advised that you inspect your roof regularly as the seasons change. When inspecting your flashing keep an eye out for the signs of defects listed above. If you believe your flashing has been weakened, you should always consult with a professional.

Lead flashings and the party wall act

The party wall act considers certain works notifiable and therefore requires a party wall notice to the adjoining neighbours. The type of notifiable work usually involves, excavating near the party wall, cutting into or building on the party wall and building on or up to the boundary. 

A building owner undertaking works may want to cut into the party wall to install flashings at the junction where the two properties meet.  This is done to weatherproof the junction, if they are unable to do this the building could be susceptible to water ingress which could be difficult to solve. 

It is not uncommon for adjoining owners to be concerned about this as they believe they have legal rights over their walls. However, the Party Wall Act is not to hinder construction projects and was created as a way to resolve disputes. 

If the adjoining neighbour does not consent to the works the building owner will have to adhere to the party wall act and will need to serve a party wall notice under Section 2(2) (f) or (j)  in advance of two months. Your neighbour cannot stop you from exercising the rights given to them by the act. However, they can consult a party wall surveyor to agree on the Party Wall Award. The Party Wall Award may contain directions on when and how the work is done. 


Mr Jones and Mrs Bens are neighbours in semi-detached houses they share a party wall separating the two properties. Mr Jones decides to undertake a rear extension however the extension requires new flashing along the party wall.  Mr Jones consults a party wall surveyor to prepare the correct notice to serve Mrs Bens. Mrs Bens receives the notice and decides to appoint her surveyor. The surveyor advises Mrs Bens on her rights and options.  She decides to consent to the work. With the guidance of their surveyors, they enter into a Party Wall agreement. The agreement outlines the scope of the work, access, working hours etc. Both parties sign the award. Following this the contractors install the flashings by their Party wall award. 

If you are planning a rear extension, it is important to make sure that the flashing is installed properly and that the Party Wall Act is followed. As this will prevent future issues for both you and your neighbour. 

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