Why it happens
Some houses were built with only a flimsy partition, or nothing at all, between the roof spaces. In others the wall was damaged or partly taken down over the years.
Why it matters
- Fire: a gap lets fire and smoke pass between houses.
- Security: someone could get from one loft into the other.
- Sound and heat: noise and draughts travel through.
Loft conversions
Building control will usually expect proper fire separation between your loft and next door's as part of a loft conversion. Building up, completing or rebuilding the party wall is work to a party structure, so a party structure notice is needed.
Who pays
Where the work is needed because the wall is defective, the Act allows a split of the cost, reflecting how each house benefits from the wall and who let it fall short. If you are doing it as part of your own project, expect to pay. The surveyors settle any disagreement.
For neighbours
If the gap is found during next door's loft conversion, they should serve notice before building up the wall. The work should improve your home's protection too.
Common questions
Can I simply put up a stud wall in the gap?
For fire separation, building control will usually need a wall of suitable construction. Ask them, and serve notice if the work is to the party structure.
Where this comes from in the Act
- Section 2: Repair etc. of party wall: rights of owner
- Section 3: Party structure notices
- Section 11: Expenses
Links go to the official text of the Party Wall etc. Act 1996 on legislation.gov.uk.