No, it is optional. A certificate of lawfulness is the council's written confirmation that work is lawful in planning terms, usually because it falls within permitted development. It is worth having when the case is close to a limit or you expect to sell within a few years.
If your extension fits within permitted development, you do not need to tell the planning department anything. There is no form to fill in and no fee to pay. A certificate of lawfulness is what you apply for when you want that in writing.
The two kinds
The Town and Country Planning (Scotland) Act 1997 provides for two certificates.
- A certificate for proposed development covers work you have not started. You send the drawings, the council checks them against the rules, and if they comply it issues a certificate saying the work would be lawful.
- A certificate for existing development covers something already built. It is used where work has been in place for long enough that enforcement can no longer be taken, or where someone needs to show that an existing extension was permitted when it went up.
For a homeowner planning an extension, it is the first kind that matters.
When it is worth applying
Most straightforward single-storey extensions do not need one. A room set well back from the boundaries, on a detached house outside a conservation area, is obviously within Class 1A, and a certificate adds little.
It earns its fee in a few situations:
- The design is close to a limit. A flat roof that will finish just under 3 m at the eaves on sloping ground, or a part within a metre of the boundary that reaches exactly 4 m back. If a neighbour complains later, a certificate settles it.
- The plot’s history is unclear. On newer estates, the original planning permission sometimes removed permitted development rights. A certificate application makes the council check.
- You may sell soon. Buyers’ solicitors increasingly ask for evidence that an extension did not need planning. A certificate answers that in one document.
- The factory needs certainty. Once modules or panels are made to a size, changing it is expensive. Some homeowners prefer to have the planning position fixed before paying the manufacturing deposit.
What to send
The application goes to the council’s planning department, usually through the national ePlanning service. Send:
- a location plan with the property outlined;
- existing and proposed floor plans and elevations, with heights measured from the lowest ground next to the extension;
- a short statement saying which class of permitted development you are relying on, normally Class 1A for a single storey, and how the design meets each limit.
That last part matters. The council decides only what it is asked. A clear statement that walks through the depth, eaves, height, footprint and garden tests makes a quick decision more likely. Our page on permitted development in Scotland sets out each limit.
The fee and the wait
The fee is set nationally as part of the Scottish planning fee scale; check the current figure on ePlanning when you apply. Councils aim to decide these applications within two months, and straightforward ones are often quicker.
What it does not cover
A certificate of lawfulness is about planning only. It says nothing about how the extension is built. A building warrant is still needed before anyone starts on site, with a completion certificate at the end, however clearly the extension falls within permitted development.
It also does not override title conditions. If your title deeds restrict building in the garden, or the land at the back is shared, the certificate does not change that. Those are questions for a solicitor.
A practical order of events
For most people choosing modular extensions Scotland-wide, the sensible sequence is: survey, design, decide whether the planning position is clear-cut, apply for a certificate only if it is not, then submit the building warrant. The two applications can run at the same time, which keeps the factory slot within reach.