Four metres, then a 45 degree line
Perth and Kinross Council is unusually clear about what it will accept at the back of a house. Its Placemaking Guide, adopted in March 2020, says a single storey rear addition 4 metres deep from the original back wall would in many circumstances be acceptable, even right on the boundary. Go deeper and the wall has to step away from the neighbour at 45 degrees, measured from that 4 metre point.
The guide relaxes this where your neighbour sits to the south of you, so you would only shade them from the north, or where no habitable room window of theirs is affected. Two other numbers matter. Windows of habitable rooms should generally sit at least 9 metres from the rear boundary they look over, unless there is proper screening. And a new ridge should not normally rise above the original one. Lower is better.
Building tight to the boundary can be fine if the neighbour agrees, but the council asks you to think about how that wall gets maintained in twenty years. Talk to next door early. It costs nothing and saves a planning objection.
Two sets of rules, both Scottish
Placemaking Guide pages are what a planner uses when you apply. Before that, check whether you need to apply at all. Scotland's permitted development order, explained in the Scottish Government's Circular 1/2024, lets a house (not a flat) add a single storey at the back without permission. Where any part comes within a metre of the boundary, it can project 3 metres on a terraced house or 4 metres on a semi or detached one, with eaves under 3 metres and an overall height under 4. The house can't end up covering more than twice its original footprint, and you can't build over more than half the rear garden.
None of that applies inside Perth Central or Kinnoull, the city's two conservation areas. There, every extension is a planning application. A listed house will normally need listed building consent as well. Whatever planning says, extending a home needs a building warrant from the council's building standards team at Pullar House before work starts, and a completion certificate when it is finished.
How each type sits on a Perth house
Roughly in the order Perth homeowners ask about them. Each one links to a longer guide.
Single storey at the back. Perth's 4 metre benchmark and the Class 1A limits line up well on a semi or detached house in the suburbs or on the newer streets out towards Bertha Park. Measure from the original rear wall, not from an old conservatory.
Kitchen. Big glass doors facing a short garden are where the 9 metre window rule comes in. Roof glazing or a screen fence usually answers it.
Planning and warrant. Check Class 1A or 1B first, then read the Placemaking Guide pages on householder work. The building warrant is separate and comes from Perth and Kinross Council, applied for through the eBuilding Standards portal.
Open plan. Knocking through the back wall of a sandstone villa off Dundee Road or Barossa Place is structural work. The engineer's design for the steel goes in with the warrant application.
Wrap-around. The rear leg can use the 4 metre allowance. The side leg is judged harder, because the council wants a clear gap kept between neighbouring houses.
Side return. On a Perth semi the guide asks for a side addition set back from the front wall, with a lower ridge, so it reads as an add-on rather than a terrace forming along the street.
Two storeys. Class 1B needs every part 10 metres clear of the boundary, so most city houses will apply. The council says a two storey rear addition can be approved where the plot can take it and neighbours keep their light and privacy.
Downstairs bedroom. Start with an assessment by the council's Occupational Therapy Team. Its scheme of assistance doesn't, in principle, fund extending a house, but it can fund an extension for a bathroom where the existing house can't be adapted. Caledonia Care & Repair helps private owners with quotes and the grant paperwork.
Home office. A detached garden room in either conservation area is limited to an 8 square metre footprint, or 4 beside a listed house. An attached room avoids that cap but needs permission there anyway.
Cost. No Perth price from us. Stone to match, a flood check or a tree survey can each shift the budget, so ask three builders to see the site.
Flood gates, burns and trees
Perth's flood scheme guards the city from the Tay and from the Scouring and Craigie Burns, with 77 flood gates. A 2025 council flood study notes that the defences held in 2005 and 2006, but water still gets in another way. Surface water reached about 165 properties in August 2020, and in October 2023 about 63 homes and caravans flooded inside. Along the Craigie Burn, the council's own study puts up to 57 properties at risk in a 1 in 200 year flood. If you live near the burn, Bridgend or the low ground by the river, look up SEPA's flood map and ask the planners before paying for drawings. The council strongly advises talking to them before you apply.
Trees are the other trap. Local plan Policy 40 expects a tree survey by a qualified professional with any application where trees stand on the site, and trees in conservation areas are protected. On the edge of the city, the Green Belt policy asks that any extension be of a suitable scale and form for its setting.
Where these facts come from
- Perth and Kinross Council: Placemaking Guide, supplementary guidance (adopted March 2020)
- Scottish Government: Circular 1/2024, householder permitted development rights
- Perth and Kinross Council: Local Development Plan 2 (2019)
- Perth and Kinross Council: Strategic Flood Risk Assessment (2025)
- Perth and Kinross Council: flood risk and flood risk assessments guidance
- Perth and Kinross Council: Scheme of Assistance for private sector housing (2020)
- Perth and Kinross Council: adapting homes
- Perth and Kinross Council: conservation areas
- Perth and Kinross Council: applying for a building warrant
- mygov.scot: building warrants
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Questions people in Perth ask
Our neighbour on the north side has a kitchen window facing our garden. Does that change what we can build?
Possibly. That 45 degree line exists to protect neighbours' habitable room windows. If your extension sits north of them, or no such window is affected, the guide allows the rule to be relaxed. A planner will look at the drawings, so show the neighbour's windows on them.
We live near the Craigie Burn. Will that stop us extending?
Not automatically, but expect questions. A council flood study lists properties along the burn as at risk and has proposed upgrading the culvert at Queen's Avenue. Check SEPA's map and speak to the planning team before you commission an architect.
Our house in Kinnoull is in a conservation area. Can we put up a small single storey kitchen without applying?
No. Scottish permitted development for extensions doesn't apply in conservation areas, so even a modest rear addition needs planning permission. You will need a building warrant as well.
Can we build our extension right up to the boundary wall?
Placemaking guidance says a wall on the boundary may be acceptable with your neighbour's agreement, up to around 4 metres deep. Think about access for gutters and pointing later, and remember the building warrant is a separate approval.