The short answer
Yes. Your half of a semi-detached roof belongs to you, so you can have it re-covered while your neighbour's half stays as it is. The work stops at the party line, the shared edge where the two roofs meet, and the new covering is finished against the old one with lead and a tidy ridge end. The detail at that join decides whether the result looks right and stays dry.
A semi has one roof shared between two owners. Doing one half is routine, as long as the join down the middle is planned before a single tile comes off.
Where your roof ends and theirs begins
A semi-detached roof usually runs as one covering across both houses, with a ridge along the top, the horizontal line where the two slopes meet. Beneath it a masonry wall rises between the homes, and that wall is the party wall. The party line is the place where the wall meets the roof. Everything on your side of that line is yours to repair or replace.
Will a new roof on my side disturb the neighbour's?
It should not. We strip the old covering back to a clean edge a little way from the party line, so the neighbour's slates or tiles are never lifted by accident. The survey is where we study how the two halves were joined: whether the battens, the narrow timbers the covering is nailed to, run straight across or stop at the wall, and how the ridge ends. Photos of that junction go into your survey pictures, so you see what we will be working beside before any price is given.
If your neighbour's side looks tired, mention what the survey shows. A freshly cut edge is exposed for a day or two, and a neighbour who knows what is happening is a calmer neighbour. Our roof replacement page covers whole-roof jobs.
Matching the half that stays old
This is what owners worry about: will two halves look odd together? New covering is cleaner and a shade different from tiles that have weathered for decades, so the answer is that the colour will differ at first.
Should the new tiles match the neighbour's?
Where the profile and material are the same, matching works well. The same shape of tile, or the same size of slate, keeps the courses running across the roof in a straight line. The colour settles as the new covering weathers. A reclaimed tile or slate from a rear slope can sit at the visible edge if that match matters to you.
Changing material is another decision. Swapping clay for concrete or slate for tile alters the look of the house, and appearance is a planning matter. Class C of the permitted development order usually deals with a straight swap of covering, whereas a different material may fall outside it, so check with Somerset Council's planning team first. In a conservation area, or on a listed home, ask before choosing anything. Our answer on changing slate to tiles goes further.
The join: ridge, verge and flashing
The line between old and new is where a half re-roof either succeeds or leaks. Three parts matter.
What happens at the ridge and the verge?
The ridge tiles along the top stop short of the party line and finish with a neat end, leaving the old ridge beside it undisturbed. At a gable end, the sloping side edge of the roof is called the verge. On a semi, the party line behaves like a shared verge. The new covering is cut and bedded against the old, and a flashing, which is a lead strip worked over the junction, makes sure water runs off the new roof without creeping under the old one.
Lead is the usual choice, and it "can last for over 80 years" (MyJobQuote, Sep 2026), well beyond what the new covering needs, so the join is not the weak point in the next generation of the roof. Your neighbour's side is not made weaker by the work, because the flashing sits on their covering and does not cut into it. If the party wall carries a chimney, the stack needs separate attention at the survey, since it affects both houses.
Party wall, notices and Building Regulations
Re-covering your own half does not normally call for a party wall notice. The Party Wall etc. Act 1996 applies when the work touches the shared structure. GOV.UK lists notifiable work as including "removing chimneys from a party wall", and two months' notice is required ahead of the start under section 3. Take those questions to a party wall surveyor, because building control does not deal with them.
Does a half re-roof need Building Regulations approval?
The Planning Portal's test has two limbs: under 25 per cent of the building envelope and under 50 per cent of the roof. Staying under both normally means no building control application is asked for. Somerset Building Control has not published a re-roofing threshold. If the new covering is 15 per cent or more heavier, for example slate replacing light tiles, approval and a structural opinion come into play.
When in doubt, your building control body will advise; Somerset Building Control is on 0300 303 7790. After the survey we mark on the plan where the new roof stops and your neighbour's begins, and your price is built on that plan.
Half-roof worries answered
Must I tell the house next door before work starts?
No rule asks you to, unless the work touches the party wall, such as a chimney on it. It is still sensible. Scaffold may sit near their boundary, the roof edge is open for a short time, and a friendly word beforehand stops the first morning coming as a surprise.
Will the roof look uneven with one half new?
For a while, yes, because new slates or tiles are cleaner than weathered ones. Matching the profile keeps the lines straight, and the colour difference softens as the new covering weathers. Reclaimed material at the visible edge can help where the match matters to you. We talk through the options after the survey.
The full picture: Roof replacement and new roofs in Taunton ยท More short answers