How did you work out if your project was permitted development?

[GianVirdi]

I'm an architectural designer (10+ years in practice) and I'm trying to understand how homeowners actually navigate permitted development. The council website is often confusing, guidance online is patchy, and I keep hearing different versions of "we weren't sure so we just submitted a planning application to be safe."
If you've been through this recently - how did you figure out whether your extension, loft, or outbuilding fell under PD? Did you submit a planning application you didn't need to? Did you skip it and hit a problem later? Did someone help you work it out?
Genuinely just trying to learn. Happy to answer PD questions in the thread as a thank you.

personally I would ask the local planning department via email so their response is in writing. I would never rely on a builder, architect (no offence) for advice on the matter.

We emailed the local planning department with photo's and descriptions of what we wanted to do then the builder did it.

I just looked up the exempted conditions and made sure that what we were planning was covered by them in terms of height, square footage, windows etc. An architect friend drew up our plans for us, anyway, but we'd already established our proposed extension was exempt.

I emailed them. Lots of people in the street had applied for planning but I didn't think it looked like we needed to. They replied within a couple of days saying I was correct and others had done it just because they thought they should.

This

I read the rules and made a decision.

Pure guesswork.

Or... look at the local authority planning website to see if they have the permitted development information there. Or Google. Or use the Planning Portal.

Information is available.

Really useful, thank you. For those who emailed the council - did you find their response was definitive, or more of a general steer? I've heard the advice can vary quite a bit depending on who replies.

Why don't you just phone the council and ask the question? They may advise you to apply for prior approval or certificate of lawful development but should be able to direct you to where the information on permitted development is on their website or in the regulations.

Read the permitted development legislation and the associated technical guidance. Sometimes there is a slightly grey area (e.g. is a lean-to shed an extension or outbuilding) which needs a bit more googling.
A lot written on the internet is wrong - so go to the source facts.

Even as an Architect I would always submit to planning to check whether a proposal meets PD rights.
Even if I know it’s all fine my PI insurance wouldn't be valid without it

My council charge for advice, so that's a factor. But the cost of planning vs permitted development applications is not that much, so I can see if there is any doubt that a planning application would make sense. The council is 'pro-development'.

on the flip side many plans go in that are then built differently. E.g. PD for a loft extension, but then build up a party wall (technically not PD)

As a planner of over 30 years, I would never give a definitive answer without having seen all the relevant council records - past planning permissions for the property, article 4 directions etc.
Most Councils will not give an informal answer, but will want an application for a certificate of lawfulness submitted in order to make a legal decision.
If you're willing to take the risk of deciding on your own, then I definitely recommend looking at the formal government guidance (assuming your are dealing with sites in England - the other nations may have similar guidance)
https://www.gov.uk/government/publications/permitted-development-rights-for-householders-technical-guidance/permitted-development-rights-for-householders-technical-guidance#class-a-enlargement-improvement-or-alteration