Extensions constructed alongside an existing neighbouring wall often need careful roof detailing.
Homeowners sometimes ask whether they can simply install flashing into the neighbour’s wall or attach parts of their new roof to it.
The answer depends on ownership, the status of the wall and the exact works proposed.
First establish what the wall is
A wall that appears to sit at the boundary could be:
- entirely owned by your neighbour;
- entirely owned by you;
- a party wall; or
- a party fence wall.
Our guide explaining what a Party Wall is sets out the statutory definitions.
The Party Wall Act does not itself decide where the legal boundary lies. For more on that distinction, see Do Party Wall Surveyors Determine Boundary Lines?.
Cutting flashing into a party wall
Certain works to a party wall can fall within the rights provided by the Party Wall etc. Act 1996.
Where cutting into a party wall is proposed, notice may be required.
Our Section 2 guide specifically discusses cutting into shared walls and installing flashings.
What if the wall belongs entirely to the neighbour?
You should not assume that the Party Wall Act gives you a general right to attach your extension to a wall wholly owned by someone else.
Ownership and statutory rights need to be considered carefully.
Weatherproofing is important
Poor roof abutment details can result in leaks affecting either property.
The drawings should clearly show how the new roof meets the neighbouring wall and how the junction will remain weatherproof.
Access may be needed
Some flashing and roof works are difficult to complete entirely from your own side.
Our Party Wall Access guide explains when access rights may arise under Section 8.
Simple Survey can review the detail
Visit our Party Wall Surveyor service page and send us the proposed roof detail before construction starts.