You've measured the garden.

You've looked at approximately 47 pictures of extensions online.

A builder has said, “Yeah, shouldn't be a problem.”

Excellent.

Now comes the slightly less exciting question:

Do you actually have permission to build it?

Not every extension, loft conversion or garden room in Peterborough needs a full planning application.

But “it's only small” isn't a planning rule.

Before spending money, there are two separate things you need to understand: planning permission and building regulations.

And no, unfortunately they aren't two names for the same thing.

Planning permission and building regulations: what's the difference?

Think of planning permission as being concerned mainly with what you're changing and how that development affects the property, surrounding area and neighbours.

Building regulations are technical standards concerned with how the work is designed and constructed safely and properly.

They can cover things such as structure, fire safety, insulation, ventilation and drainage.

That means your project might need:

planning permission, building-regulations approval, both - or sometimes neither.

This is where the phrase “I was told I didn't need planning permission” can cause trouble.

That might be completely correct.

It doesn't necessarily mean you're free to start building.

Building an extension? Measurements matter

Some extensions can be built under permitted development rights.

Permitted development essentially means planning permission has already been granted nationally for certain types of work, provided you stay within all the relevant rules and limits.

Those rules can involve:

• how far the extension projects;

• its height;

• its position;

• proximity to boundaries;

• how much land around the original house is covered; and

• previous extensions or additions to the property.

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Side and rear extensions can also be treated differently.

So don't look at a neighbour's extension and assume:

“Mine's smaller than that, so I'll be fine.”

Their property may have a different planning history, different boundaries or different permitted-development rights.

For some larger rear extensions, there is also a process known as prior approval.

In simple terms, that's a procedure where the council considers particular aspects of a development before it goes ahead.

 It isn't the same as simply building without contacting anyone.

Measure first. Check second. Order the bifold doors later.

Loft conversion? ‘No planning’ doesn't mean ‘no approval’

Loft conversions provide a particularly good example of why the two systems matter.

Some loft conversions can fall within permitted-development rules, depending on things such as the additional roof volume, height and position of dormers.

But turning your loft into a proper habitable room will normally bring building regulations into the picture.

Building control may need to consider structural strength, stairs, insulation and fire safety, among other requirements.

So you can quite legitimately discover:

Planning permission: not required.

Building-regulations approval: required.

If the loft is going to become a bedroom, office or other proper living space, check both before work begins.

Discovering halfway through that the staircase presents a problem is considerably less enjoyable than discovering it on a drawing.

A ‘garden room’ isn't automatically exempt

Garden rooms have become incredibly popular.

Office. Gym. Teenage den. Somewhere to work while pretending you can't hear what's happening in the main house.

Many outbuildings can be covered by permitted-development rights.

But again, there are conditions.

The building's size, height, position and intended use can all matter.

Something close to a boundary can face different height restrictions, while a building intended to become separate living accommodation raises very different questions from a shed containing a lawnmower and six tins of paint nobody remembers buying.

The name used by the company selling it doesn't decide the planning position.

“Luxury garden studio” may sound nicer than “large building at the end of the garden”, but planning rules are disappointingly resistant to marketing.

Peterborough has another thing to check: Article 4

Here's one bit of planning terminology worth knowing locally.

An Article 4 Direction allows a council to remove particular permitted-development rights from specified properties or areas.

Peterborough City Council says it has 56 Article 4 Directions covering 334 residential properties.

Depending on the particular Direction, work that might normally be permitted development can require a planning application instead.

That can include changes involving things such as windows, doors, roofs, extensions, porches, walls, fences, parking areas or how a property is used.

This is exactly why:

“My mate did the same thing without planning permission”

is not particularly reliable planning advice.

Your mate doesn't live at your address.

Listed building or conservation area? Check again

Extra controls can also apply if your home is listed or within a conservation area.

A listed building is one included on the national heritage list because of its special architectural or historic interest.

Listed-building consent is a separate form of permission that can be required for work affecting the character of a listed building.

Conservation areas are places given additional protection because of their special architectural or historic character.

If either applies to your Peterborough property, don't assume the ordinary rules you've read for another house will automatically apply.

Get property-specific advice.

And then there are building regulations

For work requiring building-regulations approval, Peterborough Building Control provides different application routes.

You may come across Full Plans, where detailed plans and information are submitted for checking, and a Building Notice, which can be used for certain types of work without the same advance approval of detailed plans.

A Building Notice does not mean the regulations disappear.

The finished work still needs to comply.

There is also a regularisation process for certain work that was completed in the past without the required building-regulations approval.

That's a retrospective route essentially dealing with approval after the event.

It's useful that such a process exists.

It's considerably less useful as a home-improvement strategy.

Finished work may need to be inspected or opened up, and problems can become much more expensive to correct once everything has been plastered, painted and furnished.

Do this before accepting the builder's quote

Before committing to the project, write down exactly what you're proposing.

How big is it?

How high?

Where is it in relation to the boundaries?

What will the space be used for?

Are you changing the structure of the existing house?

Then check the national Planning Portal guidance and Peterborough City Council's planning and building-control information for your particular property and proposal.

If you're still uncertain, get advice from the council or an appropriately qualified planning or building professional.

And there's one final wrinkle.

Planning permission isn't the only restriction that can affect what you're allowed to do.

A lease, freeholder's rules or a restrictive covenant can impose separate requirements.

A restrictive covenant is a legal restriction attached to land or property that can limit what an owner is allowed to do with it.

So receiving planning permission doesn't necessarily override every other legal restriction affecting your home.

Check first. Build second.

For most Peterborough homeowners, that's the useful rule.

Check planning permission.

Check permitted-development rights.

Check whether Article 4, listed-building or conservation-area controls apply.

Check building regulations.

Then get the tools out.

It might add a little time at the beginning.

But it's considerably easier than standing in a beautiful new extension six months later while somebody asks:

“You've got the paperwork for this, haven't you?”

What's confusing you about your Peterborough project?

Planning terminology can become complicated surprisingly quickly.

If you're considering an extension, loft conversion, garden room or other home improvement, tell us which part of the process you find hardest to understand.

Don't post your full address, plans, title documents or other private information.

Recurring questions could help shape our next plain-English Peterborough property guide.

This is general information rather than advice on whether a particular project requires permission or approval. That depends on the individual property and proposed work.

Post your comments below plus we have given you some helpful resources.

1. Apply for planning permission

2. Conservation - Article 4 directions

3. Building regulations advice

4. Planning Permission - Extensions

5. Planning Permission - Loft conversion and Outbuildings

6. Planning permission and building regulations - Loft conversion

7. Listed Building Consent (PF11)