Do I need to apply for planning permission for my new loft conversion?

I live on the south coast in a small townhouse and recently built an attic conversion with a dormer window in the back.

The council says the extension was not built correctly because it protrudes slightly above the top of the roof, so you can see it from the street.

They say it probably won’t get planning permission and I might have to lower the roof, but my contractor says that would cost thousands.

He only built the roof that little bit extra because he needed to add some extra insulation and because it only sticks up about 2 inches. You can’t really see it from the front and I don’t really understand why the municipality thinks it’s so important. Do I have to apply for a building permit or try to argue with the municipality that it is not a problem?

MailOnline Real estate expert Myra Butterworth replies: Loft conversions can seem attractive because in most cases planning permission is not required.

But difficulties can arise if details are not observed. We talk to a planning expert about your options and how you can best proceed, given that the extension has now been completed.

Martin Gaine, a chartered urban planner, replies: An attic conversion is one of the best ways to add a lot of extra living space to a small townhome.

In most cases you don’t even need planning permission – a typical conversion with Velux type skylights to the front and a dormer window – a sort of extension set at right angles to the rear roof pitch – to the rear is permitted.

Even better, the allowed development rights for roof extensions are very generous, meaning you can build much larger dormers than municipalities would normally grant planning permission.

Even the smallest deviation from the allowed development rules means that the entire development is illegal and needs permission

Difficulties arise if your development does not comply with the allowed development rules in every detail. Even the smallest deviation means that the whole development is illegal and needs permission. I’m afraid any increase in the height of the ridge – the highest part of the roof – means your development will need full planning permission.

It seems unjustified that the municipality suggested to you that if you applied, permission would not be granted. I advise you to apply anyway, as the only real alternative is to undo the works you have done. If the municipality rejects your application, you can appeal to the planning inspectorate.

It must be frustrating that 5 cm of roof insulation causes you such problems. You say you can’t really see it from the front – if that’s true then I think you have a good chance of getting planning permission, either through an application to the council or through an appeal.

While 2 inches doesn’t sound like much, a small change in the ridge height of a townhome can look odd if the ridge rises above an otherwise neat and uniform roofline. Victorian terraces are all about symmetry and balance, so small changes can seem out of place. If the houses in your street are very similar and your roof now looks different from the street than that of your neighbours, an urban planning application cannot succeed.

If you decide to follow the council’s advice not to apply, you may be able to convince the council not to take any further action. Although the municipality has decided that the development is illegal, it is not obliged to act against it; it could decide that it would not be ‘opportune’ (in the public interest) to proceed. You could also try to convince them that the 5 cm is ‘de minimis’, so trivial that it is not worth considering.

Try to make an appointment with your enforcement officer. Files are more sympathetic and therefore more likely to use their discretion to take no further action once they have met the homeowner. It’s much easier to be heavy handed from a distance and from behind a desk.

Talk to your councilors too, as they represent individual residents against the bureaucratic machinery of the council and can help you get a fair hearing.

If all else fails, I am sorry to say that you must reverse the works you have done. Depending on how the municipality handles it, this may mean lowering the ridge or removing the roof extensions (including the dormer window).

Schedule enforcement can have serious legal and financial implications. It is important that you seek independent advice, for example from a lawyer or planning consultant, about the particulars of your own situation.

Martin Gaine is a chartered urban planner and author of ‘How to Get Planning Permission – An Insider’s Secrets