Installing flashing on to your rear extension

What is flashing (Weatherproofing)?


Flashing is the method/process used to waterproof a structure’s joints and makes up part of a weather resistant barrier system. Flashing is used to prevent water penetration through objects such as chimneys, vent pipes, walls, windows and door openings. Typical flashing is made from lead, aluminium, copper, stainless steel or zinc alloy – new material is always being introduced to the industry.

When is flashing required?

Builders will generally use flashing on the small gap between two extensions; they need to have vertical and horizontal flashing at the top of the floor or in the case where there are two different extension heights the top section to block off the gap. This is done to prevent build-up of dirt, debris and limit access to vermin in the small gap. This will also limit/reduce any water ingress to both extensions.

When building an extension you will need to ensure there is flashing between your neighbour’s extension party wall. When doing a loft conversion you will need to make sure there is adequate flashing on your neighbours loft conversion Party Wall.

Different Types of Flashing

There are many different types of flashing that you might require and come across, the most common types are:

Roof flashing

Placed around ends or objects which protrude from the roof of a building to direct water away from joints and in valleys where the runoff is limited.

Wall flashing

Often embedded in a wall to direct water that has penetrated the wall back outside. In some applications, it is applied to prevent the entry of water into the wall. Wall flashing is typically found at interruptions in the wall, such as windows and points of structural support.

Planning permission or consent for installing flashing

Planning permission is not required when installing flashing, but you need to serve notice under Section 2(2) (f) or (j) under the Party Wall etc depending on the wall. Obviously there are other sections to serve for the Excavation and building on the Line of Junction which is not related to this topic.

Find a Party Wall Surveyor to help you better understand what paperwork and processes are required before you start any works.

Avoid future Issues

If you or your neighbour are planning an extension, make sure the flashing and weather proofing is implemented properly. The correct implementation of a weatherproofing and flashing can avoid future issues for both your property and your neighbour’s.

Are you installing flashing on to your rear extension adjoining your neighbour? Do you need to find a Party Wall Surveyor in London? Contact Seven One Associates to get help and support on how the works will be affected by the Party Wall Act.

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