Architectural designer FAQ: the questions Derbyshire clients ask us every day

Not always. A lot of single-storey extensions are covered by Permitted Development, which means you can build without a planning application as long as you stay inside the size limits and your house still has its Permitted Development rights. Two-storey extensions, and anything that faces the road, usually do need planning permission.

If you do need it, for an extension to your own house it's called a householder application, and it's the simplest kind there is. The council looks at size, appearance and the effect on your neighbours (their light, their privacy) and makes a decision, normally within 8 weeks of the application being validated.

There's a lot of small print, and we've covered it in two places: do you need planning permission for your project, and our longer guide to planning permission, which goes through fees, conditions, refusals and appeals.

Permitted Development rights let you do certain work to a house without applying for planning permission, things like modest extensions, loft conversions and porches. Most houses have them. Flats and maisonettes don't, and the rights can be removed by a planning condition or an Article 4 Direction, or reduced in a conservation area or national park, or on a listed building.

The limits for a single-storey rear extension are 3 metres from the original back wall on a semi or terrace, and 4 metres on a detached house, with a maximum height of 4 metres. A side extension has to be single storey and no wider than half the width of the original house. There's also a prior approval route that lets a single-storey rear extension go further (6 metres on a semi or terrace, 8 on a detached house) if you notify the council first and the neighbours' objections don't stand up.

Notice the word original. The limits are measured from the house as it was first built (or as it stood on 1 July 1948 if it's older), so if somebody extended it in the 1990s, part of your allowance may already be used up.

Newer estates are the ones that catch people out. The original planning approval for the estate often has a condition taking Permitted Development away, and you'd only find it by looking that approval up on the council's planning website (we can check this for you). Article 4 Directions do the same thing in particular streets or areas, usually in conservation areas.

And do you still need drawings? The law doesn't make you get them for Permitted Development. But you'll need them for Building Regulations approval anyway, your builder needs something to price from, and if you want proof in writing that your project is allowed (a Lawful Development Certificate, which a buyer's solicitor will ask for when you sell), the council wants drawings with the application.

Planning permission decides whether you're allowed to build something at all: its size, how it looks and the effect on your neighbours. Building Regulations decide how it's built: structure, fire safety, insulation, drainage, ventilation. They're two separate approvals from two different departments, and plenty of projects need Building Regulations approval even when they don't need planning.

Garage conversions, loft conversions and removing a load bearing wall are the usual examples. No planning needed in most cases, but you still need Building Control involved. You can go down the full plans route, where they check the drawings before work starts, or a building notice, where they inspect as the work goes along. For anything with steelwork in it, full plans is the safer way. More in planning permission or Building Regulations, what's the difference.

Outline planning permission agrees the principle of building on a site, usually a new house or houses, without approving the detailed design. Full planning permission approves everything in one go. With outline, the details (called reserved matters: layout, scale, appearance, access and landscaping) have to be applied for and approved before you can start.

Outline is mostly used for selling land or testing whether a plot will get approval before spending money on a full design. But the council can still ask for a lot of detail at outline stage, so for a single plot a full application is often the better way (it's also quicker overall). You can't use outline for an extension to your own house. The full comparison is in outline planning permission vs full planning permission.

The 45-degree rule is a guideline most councils use, including the ones around Derbyshire, to check whether an extension will take too much light from a neighbour's window. If your extension crosses a 45-degree line drawn from the middle of their nearest window, it's likely to be refused for loss of light. It isn't law, but planning officers use it a lot.

It works like this. Take the neighbour's nearest window to your extension that serves a habitable room (a living room, kitchen or bedroom, not a bathroom or landing). On a plan, draw a line at 45 degrees back from the middle of that window towards your extension. On the elevation, draw a line at 45 degrees from the middle of the window too. If your extension cuts through both lines, expect a problem. Some councils only use one test for single-storey extensions, so check your council's design guide.

It's mostly two-storey rear extensions on semis and terraces that fall foul of it, because the extension sits right next to the neighbour's back windows. Single-storey extensions usually pass. And there's often a way round it, a hipped roof, setting the upper floor in from the boundary or making the first floor shallower than the ground floor. We check this before anything goes in to the council.

Under Permitted Development, a single-storey extension can be no higher than 4 metres, and no higher than 3 metres at the eaves if it's within 2 metres of a boundary. An extension of more than one storey can't have eaves higher than the existing house, and no extension can have a ridge higher than the existing roof.

Those are the Permitted Development limits. If you need planning permission anyway, there's no fixed height, the council judges the design on its merits, but they'll still expect an extension to sit lower than the main roof in most cases (it's called being subservient). So matching the ridge height is about as far as you'll normally get.

If you want to add a whole storey on top, there's a separate Permitted Development right for that on houses built between 1948 and 2018: up to two extra storeys on a detached house, one on a semi or terrace. It needs prior approval from the council, which looks at the design and the effect on the neighbours, and it doesn't apply in conservation areas.

A coal mining risk assessment is a report that goes in with a planning application when the site is in a Development High Risk Area, meaning old coal workings or mine shafts could affect the ground you're building on. It looks at what's under the site and what you'll do about it. Without one, the council will return the application as invalid.

It comes up a lot in Derbyshire. Alfreton, Ripley, Heanor, South Normanton and Pinxton all grew up around collieries, and the coalfield runs underneath a big part of Derbyshire and Nottinghamshire. Some of the old workings are shallow, and there are recorded mine entries (shafts and adits) that nobody would know were there by looking.

You can check your site on the Mining Remediation Authority's interactive map by postcode (it was called the Coal Authority until 2025, so older guidance uses the old name). Not every application in a high risk area needs a full assessment. There's an exemptions list, and most householder applications (extensions to your own house) are on it, but new houses and most other development aren't. Your council's validation checklist will tell you which applies.

We can prepare the assessment and submit it with your application. There's more in coal mining risk assessments.

A Tree Preservation Order (TPO) is made by the council to protect a particular tree, group of trees or woodland. If a tree is protected, you need the council's consent before you cut it down, lop it, top it or damage its roots. Trees in a conservation area are protected too: you have to give the council 6 weeks' notice before doing any work to them.

It matters for an extension because roots spread a long way, and digging foundations near a protected tree counts as damaging it. Your council will have a TPO map or will tell you over the phone. Full details are in tree preservation orders and what they mean for your project.

It depends how it's used. Letting out your own cottage now and then usually doesn't need planning permission. Using a house full time as a holiday let can be a "material change of use", which does need permission, and the council decides that on the facts (how often it's let, how many people, the effect on the neighbours).

If the building isn't a house yet (a barn, a stable block, an old chapel) it definitely needs planning permission, and in the Peak District National Park the rules are tighter again. The safest thing is to apply for a Lawful Development Certificate, so you have the council's answer in writing before you spend money on it. Give us a call and we'll look at your particular cottage.

The Party Wall Act 1996 says you have to give your neighbours written notice before you work on a wall you share, build a new wall on the boundary, or dig foundations near their house. If they agree in writing, that's your agreement. If they don't agree, or don't reply within 14 days, surveyors draw up a Party Wall Award instead.

There are three types of notice. Work to the party wall itself (cutting in a steel beam, for example) needs 2 months' notice. A new wall on the boundary line needs 1 month. And a Section 6 notice, also 1 month, covers digging foundations within 3 metres of your neighbour's building and deeper than theirs, or within 6 metres if a 45-degree line from the bottom of their foundation would hit your excavation. That's the one most extensions need.

Be careful with templates you find online. A notice with the wrong details or the wrong timescale isn't valid, and you'd have to serve it again and wait again. We serve notices for clients through our party wall service, and there's more in the Party Wall Act explained and the Party Wall Act 1996 part two.

A principal contractor is the builder in charge of health and safety on site during construction. Under the Construction (Design and Management) Regulations 2015, known as CDM, you need one whenever more than one contractor will work on your project, which is almost every extension (builder, electrician, plumber, roofer). On a house, it's normally your main builder.

Their role is to plan, manage and monitor the building work so it's done safely. That means a construction phase plan (a written plan of how the site will be run safely), making sure everyone on site has had an induction, coordinating the different trades, providing toilets and washing facilities, and keeping the public out of the site.

Does the principal contractor need to be on site? Not every minute of every day. But they must supervise the work properly for the level of risk, so somebody competent has to be in charge whenever risky work is going on, digging foundations, putting in steels, working on the roof.

If you're a homeowner (a domestic client), the good news is most of your CDM duties pass automatically to your builder. There's also a principal designer role for the design side, which the designer usually takes on. Since 2023 the Building Regulations have their own principal contractor and principal designer roles as well, normally filled by the same people. More in CDM regulations and what they mean for your building project, and there's a downloadable guide in our documents section.

Usually not, if the work is mostly inside and you're swapping the garage door for a window and a bit of wall. You'll need planning if your Permitted Development rights have been removed (common on newer estates, where a condition keeps the garage for parking) or the house is listed. You'll always need Building Regulations approval though.

Do you need an architect for a garage conversion? No. But you do need proper drawings for Building Regulations, and someone who knows what goes in them. The floor is the big one. Garage slabs usually sit lower than the house and often have no damp proof membrane, so the floor gets raised, insulated and joined to the house's damp proof course properly. The new wall in the door opening needs a foundation (the only way to tell what's under there is to dig a hole!), and single skin walls need insulating on the inside.

People use them for a bedroom, a home office, a playroom, a utility, even a small annexe. We've written two parts on this, start with garage conversions and then garage conversions part two, which covers floors and damp proofing in detail.

Usually not. Most loft conversions are Permitted Development, as long as the extra roof space is no more than 40 cubic metres on a terraced house or 50 on a semi or detached, nothing goes above the existing ridge, and there's no dormer on the roof slope facing the road. You'll always need Building Regulations approval.

A mansard (where the back roof slope is rebuilt almost vertical) changes the shape of the roof a lot and nearly always needs planning permission. So does any loft conversion in a conservation area or the Peak District National Park, where loft extensions aren't Permitted Development at all. That catches out a lot of people in the High Peak.

The "10 year rule" people search for is about enforcement. If building work went ahead without planning permission, the council has a time limit for taking action, and in England that's now 10 years from when the work was substantially finished (it used to be 4 years for building work, until April 2024). Don't rely on it! It doesn't apply if the council can show the work was deliberately hidden. There's more on lofts in loft conversions.

Yes, and if you're using the cellar that's already there without changing the outside of the house, you usually won't need planning permission. You will need Building Regulations approval, because a habitable cellar needs proper headroom, ventilation, a way out in a fire, and waterproofing.

The waterproofing is the expensive part to get wrong. It's done either by tanking (a waterproof coating on the walls and floor) or a cavity drain membrane, which lets water in behind a membrane and pumps it away. If you're digging the floor down to get more headroom, that's underpinning, and it'll almost certainly need a party wall notice. Adding a lightwell or a new window at the front may need planning too. Start with cellar and basement conversions, and there's more in domestic cellar conversions part one.

Yes, you can, but it needs a steel beam (or similar) to carry the load the wall was holding up, designed by a structural engineer, and Building Regulations approval before you start. It is never a DIY project. Get it wrong and the floor or roof above has nothing holding it up.

How do you know if a wall is load bearing? If the floor joists above run across it, or there's another wall directly above it upstairs, it probably is. But don't guess. The engineer works out the size of the beam and the padstones it sits on, and the builder props everything up with acrows before the wall comes out. If it's a party wall or the beam sits in one, you'll need a party wall notice too.

The full explanation is in removing a load bearing wall and other internal alterations. And please seek advice before you knock anything down!!

Work out what you want the space for and what you can spend, then find out whether you need planning permission. After that it's a measured survey and drawings, planning (if needed), Building Regulations approval, party wall notices, and quotes from builders who are all pricing the same drawings.

A few things that get missed:

1. Check your deeds for restrictive covenants. They can stop an extension even when planning says yes.

2. Talk to your neighbours early, before the party wall notice lands on their doormat.

3. Find out where the drains run. Building over a public sewer needs an agreement with the water company (Severn Trent round here).

4. Tell your home insurer, and your mortgage lender if you have one.

5. Don't let the builder start before Building Regulations approval comes through. Any work done before then is at your risk.

There's more in common mistakes before a builder starts work, and if you're still deciding what to do, add space and value to your property.

Start with your title deeds, which often show the date of the first sale. Your council's planning records will show when newer houses were approved. Old Ordnance Survey maps let you see when the house first appears. And the style of the house (windows, brickwork, roof) will usually narrow it down to a few decades.

If your deeds aren't much help, HM Land Registry holds the title register and plan, but they often don't go back past the first registration, which for a lot of older houses was only the 1990s. The Derbyshire Record Office in Matlock and Nottinghamshire Archives hold old maps, census returns and building plans, and you can look at old OS maps online for free. Ask the neighbours too, especially on a street where the houses were all built together.

Why does it matter? Because the age of the house tells you how it was built: solid walls or cavity, lime mortar or cement, what's likely to be under the floor. That changes what you can do to it. The full rundown is in do you know the age of your house.

Georgian houses (roughly 1714 to 1837) are plain and symmetrical, with a flat front, sash windows with small panes, often six over six, and the windows getting smaller as they go up. Victorian houses (1837 to 1901) are more decorated, with bay windows, patterned brickwork, steeper slate roofs, bigger window panes and fancy porches.

Round here a lot of the Victorian terraces were built for the mills and the pits, so they're plainer than the London versions, but you'll still see the bay windows and the bigger panes of glass. The full comparison is in how to tell if your house is Victorian or Georgian.

Yes. Under UK law the person who draws the plans owns the copyright, even after you've paid for them. What you get is a licence to use them for the project they were drawn for. You can't hand them to another designer to copy, or reuse them for a different house, without permission.

It catches people out when they change designer halfway through a project or buy a plot with plans already drawn. The full explanation is in are your architectural drawings subject to copyright.

"Architect" is a protected title in the UK, and only people registered with the Architects Registration Board (ARB) can use it. An architectural designer does the same design work, planning applications and Building Regulations drawings, but isn't on that register. The difference is registration, not ability, and for extensions, conversions and new houses either can do it.

What matters more is whether the person has designed plenty of projects like yours and knows how your local council works. I'm Chris Froggatt, an architectural designer, and I've been doing this since 2000. We've designed over 1000 projects in that time, from garage conversions to new houses and industrial units, and we carry £1.5m professional indemnity insurance.

There's a fuller answer in do you need an architect or an architectural designer, and you can read more about Chris and ABDS.

Not always. If you're doing something that doesn't need planning permission or Building Regulations approval, you might not need drawings at all. But if it needs either, the drawings have to be accurate and complete, and a lot of applications are sent back as invalid because something is missing.

Even a small project has more in it than it looks. A modest rear extension still has a steel over the opening, drainage, and probably a party wall notice. A garage conversion still has the floor, the damp and the new foundation to sort out. So it pays to have someone who knows the regulations do the drawings, because your builder prices from them and Building Control checks the work against them.

We design small projects all the time. Sometimes the answer to your first phone call is "you don't need permission for that", and that's fine too. It's that sort of help that won us the Best of Houzz 2017 Customer Service award. Have a look at what our clients say on our testimonials page.

We're based in Swanwick, just outside Alfreton, and we cover most of Derbyshire and Nottinghamshire. That includes Derby, Nottingham, Mansfield, Chesterfield, Belper, Ripley, Heanor, Matlock, Bakewell, Dronfield, the High Peak and Burton upon Trent, and all the villages in between.

We've also designed projects further afield, including a courthouse conversion in Burnley and industrial units in Dinnington, so if you're outside that area give us a call anyway. You can see what we've designed in your area on our project pages: single-storey extensions, two-storey extensions, conversions and new builds, including the DIY SOS project in Heanor.