Likely eligible
Your answers are consistent with the principal conditions, but still require site verification, notification and Building Control work.
What the checker can tell you
Eligible if issues are resolved
A design or process item must change before the described proposal aligns with Class 3A.
Site-specific planning review required
An unknown, planning-history or Article 9 issue cannot safely be decided by questionnaire.
Not within Class 3A as described
The proposal does not fit this exemption, although Section 5 or full planning may still provide another route.
No result confirms planning permission or exempted development. A local authority Section 5 declaration is the formal route for determining whether a particular proposal is exempt. Building Regulations and Building Control obligations remain separate.
Why this page and the legal guide are separate
This checker is designed for calculator intent and applies your answers to a conservative decision tree. The 45m² exemption guide is the source-led legal-information pillar with the rule wording, limitations and updates.
Before you start
Have approximate garden area, existing shed/garage area, proposed floor area, height, boundary distances, wastewater position and planning history available. Choose “not sure” rather than guessing.
Frequently asked questions
Do I need an email to see a result?
No. The checker shows its preliminary outcome and numerical range first. Email is required only to save the detailed report and request project follow-up.
Can I run it for a model I found here?
Yes. Model pages pass the model identifier to this page so its area, supplier and price evidence can follow into your project enquiry.
Legally reviewed 2 August 2026; page reviewed 14 August 2026. General educational information only.