Solar on terraced houses
A terrace is usually a straightforward install with three specific complications: the roof planes often face east and west rather than south, the party wall is right there, and scaffolding may need to stand on someone else’s land.
Usually a straightforward install, with three terrace-specific things to settle.
Orientation. Many terraces run north-south, which puts the roof planes east and west. On our modelling that is about 79% of due south per kWp — a real loss, usually still worth doing, and better still if both planes are used.
Party wall. Only engaged if the work cuts into it. Cable routing is how that usually happens without anyone noticing.
Scaffolding. A mid-terrace may need scaffold on a neighbour’s land, and there is no statutory right to it.
Orientation: the terrace question
A terrace running north–south has east and west roof planes. A terrace running east–west has a south plane and a north one, and the south plane frequently faces the street.
| Your planes | Per kWp, against due south | What to do |
|---|---|---|
| East and west | 79% each | Use both if the budget allows — see east–west vs south |
| South and north | 100% / 54% | Fill the south plane first; north is rarely worth it pitched |
| South-east / south-west | 94% | Barely a compromise |
The east–west case is the common one and it is better than it sounds. A split array’s annual shortfall is about 21%, but the seasonal detail matters: on a June day it collects 94% of what south collects, and in December only 49%. The full picture, hour by hour, is on east–west versus south-facing.
The party wall
Most terrace installations do not engage the Party Wall etc. Act 1996 at all. An array fixed to your own rafters, on your own roof slope, is work to your own building.
It is engaged when the work cuts into the party structure — section 2(2)(f) gives a right “to cut into a party structure for any purpose”, conditional on serving a party structure notice at least two months beforehand, or obtaining written consent.
The way this happens in practice is cable routing, decided on the day by an electrician looking for the neatest run. The two-minute fix is to ask at survey stage where every cable goes and whether any of it passes through a shared wall. Full detail on party walls and solar.
Scaffolding and access
The practical constraint that delays terrace installations more than anything technical.
A mid-terrace with no side passage may need scaffold standing on a neighbour’s land, or raised over a shared alley. There is no statutory right to that under the Party Wall Act for this kind of work — it needs your neighbour’s permission as a matter of ordinary property law.
Ask early, and ask nicely. Most people say yes. Very few say yes at 48 hours’ notice with a scaffold lorry outside.
Check the front access too, if the array is on the street side. Pavement scaffold may need a licence from the highway authority, which the installer normally arranges but which takes time.
Shading in a terrace
Chimney stacks are the main event. Terraces have many of them, closely spaced, and they cast hard near shadows that move across the roof through the day. That is a different problem from a distant horizon obstruction: a stack can take out one module and, without module-level electronics, drag the whole string with it.
If your roof has stacks in or near the array area, ask specifically whether optimisers or microinverters are proposed and why. It is one of the clearest cases where they earn their cost.
Neighbouring roofs rarely shade a uniform terrace, because they are the same height. The exceptions are the ends of rows, corner plots, and terraces stepping down a hill.
Everything else is ordinary
Terraced houses are normally permitted development like any other dwellinghouse, subject to the Class A limits — 0.2 m protrusion, not above the ridge. Conservation area designation restricts walls fronting a highway, not roofs, which matters because a great many terraces sit in conservation areas: see conservation areas.
Sources
Contains public sector information licensed under the Open Government Licence v3.0.
Sorry to hear that. What was the problem?