The short answer
Sometimes. Work that stays on your own side of the roof, such as replacing tiles, felt or battens, normally does not touch the party wall. Work that cuts into the shared wall, raises it, or builds against it can fall under the Party Wall etc. Act 1996, which asks you to notify the neighbour first. These are general rules, so check your own job with a party wall surveyor before work starts.
When roof work on a semi or terrace is likely to need a neighbour notified, and the jobs that usually leave the shared wall alone.
What counts as the party wall
Where two houses join, as in a semi or a terrace, the wall dividing you from next door is shared. It usually runs up through the loft and often finishes in the roof void, where it may be raised above the tiles as a parapet or a low upstand called a party wall upstand. The Party Wall etc. Act 1996 lays down what an owner has to do before working on that shared wall, or close to it.
The Act is its own process, apart from planning permission and apart from building control, and having one of them does not stand in for the others. It is also about relations as much as rules, because it gives the neighbour a chance to know what is planned and to have the work looked at independently if they are worried.
We are roofers, not lawyers, and nothing here is legal advice. What follows is the roofer's view of which jobs touch the wall, so you know when to ask the question.
The practical point is that a party wall is a shared structure, so one owner cannot treat it as their own. Even a modest job, such as bedding a new flashing into a brick joint on the dividing wall, deserves a pause for thought. A quick message to a surveyor costs little, and it avoids a stopped job and a strained relationship with the people next door.
Jobs that normally leave it alone
Most day to day roof work stays on your side. Replacing a few slipped tiles, renewing felt and battens on your own slope, fitting new gutters and fascias, repointing your own chimney or cleaning moss off the covering do not cut into the shared wall. A full re-roof on your half of a semi is the same: the new covering lands against the wall, but the wall itself is left as it was.
The lead flashing where the roof meets the wall is the grey area. A new cover flashing fixed into a mortar joint on your own side of the wall, replacing an old one, is a small job on the face you own. Cutting new grooves into a shared masonry wall is a different job. If you are not sure which of the two your quote involves, ask the roofer to say so in writing before work starts.
Our guide to lead soakers and the page on lead apron flashing show where metal meets masonry.
Jobs that may need notice
Work that cuts into the shared wall or changes its height is where notice is likely. Examples are raising a party wall, building a new wall against it, cutting a recess to take a beam or inserting a new damp proof course. A loft conversion that rests structure on the wall, or a dormer built beside it, is also a time to ask the question early.
Where notice applies, the owner writes to the neighbour and the neighbour either consents or the two sides agree on surveyors. The Act sets time limits, so it pays to start well before any scaffolding goes up. A surveyor for either side can confirm, and many councils and building control bodies will point you towards the rules.
Raising or rebuilding the parapet above the tiles belongs in the same group, because it changes the wall itself. If you are unsure, describe the job to a surveyor in plain terms and ask whether it counts, before you pay for materials or book a scaffold.
Chimney work is similar. A chimney stack that straddles two houses is shared, so repairs may need agreement. Our answer on shared chimney stack repairs explains the practical side.
A word with next door before the scaffold
Even where the law asks for no notice, a short conversation helps. Tell next door when the scaffold will go up, what the work involves and roughly how long the roofers will be around. Scaffolding often leans towards or over a shared boundary, and the neighbour may need to move garden furniture or cars.
It also helps to record the state of the neighbour's side before work starts, with their agreement. Photos of the loft party wall, the ceiling below and the ridge line give both sides the same starting point if a question comes up later.
At the survey we photograph the roof and talk through which parts touch the wall, so the written price names the work clearly. For wider rules about roof work, see roof regulations explained, and for general background on our work visit roofing across Crawley. If your project involves a shared roof, our page on who pays for shared roof repairs is worth reading too.
More on this in Roofers in Crawley: the full guide
Two party wall questions
Do I need to tell my neighbour about a re-roof?
The law may not require notice if the wall is untouched, but telling them is still sensible. Scaffolding, noise, dust and access over their land or drive all affect them. A short note giving the start date, the expected finish and a phone number to ring avoids most disputes before they begin, and costs nothing to write.
Who should I ask if I am not sure notice is needed?
Ask a party wall surveyor before work starts, as the Act is separate from building control. A surveyor can look at the plans. Your roofer can explain which parts of the job touch the wall, and the written price should say clearly what is included, so the surveyor has something concrete to read.