All You Need To Know About House Extensions in 2023 (2023)

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If you are planning on building an extension, then you need to know the house extension rules 2023 are for building. However, don't let this detract you from choosing to build an extension. You just need to be aware of the house extension rules in place, so you can build the dream extension you have always wanted.

We are going to summarise the key factors you need to think about when it comes to building an extension.

House Extension Rules 2023

When considering a home improvement project, it is important to choose an experienced architect to guide you through the house extension rules 2023 in order to provide you with the optimised layout and external design for your property, not just to increase space, but to implement innovative designs that can physically improve your day-to-day.

Whilst there are many house extension rules to consider in 2023, they are not all that complex, but when combined together with areas of conservation, heritage, or other designated land such as metropolitan greenbelt, they can be a tricky scene to navigate. Welcome to Extension Architectures guide to House Extension Rules 2023.

One of the main considerations to determine how far you can extend is what kind of property you own. For example, terraced or semi-detached house extension rules are considerably different from those of a detached property, and this generally will relate to the impacts any extension will have on your adjoining neighbours. Another important factor of house extension rules 2023 is whether you intend to apply for planning permission or enlarge your home using your permitted development rights. These are nationally set guidelines on what you can and cannot do without planning consent from your local council, and can be tricky to navigate if you are not accustomed to the permitted development rules UK.

If you need help understanding how far you can extend or if you need planning permission for your house extension 2023, our specialist advisors are here to help!

Single-Storey Extension Rules

  • You can only cover half the area of land that is around the original house with an extension or any other type of build. This can also include a shed or outbuilding.
  • The extension cannot be forward of the side elevation or side elevation fronting a highway. This means that if you want to build your extension out toward the main road, this would require planning permission.
  • The materials used must be in line with the property’s current look, the obvious exception is a conservatory.
  • If you have a property on, what is known as, designated land then you won’t be allowed exterior cladding.
  • For a single-storey rear extension, you cannot go beyond the back wall of the original property by more than four metres.
  • The extension cannot exceed four metres in height.

Get An Architectural Quote For Your Extension and speak to an expert about what rules are relevant to you

Two-Storey Extension Rules

  • If your house is more than one storey, then if you extend, you cannot go past the back wall of the house by over three metres.
  • The maximum height of the extension’s eaves needs to be three metres if you are within two metres of the boundary.
  • The ridge and eaves height cannot be taller than the existing property.
  • The extension needs to be a minimum of seven metres away from the rear boundaries.
  • The roof pitch needs to match or be as close to the existing property as possible.
  • You need planning permission for any raised platforms, verandas, or balconies.
  • The upper-floor windows in the roof slope or wall on the side elevation need to be obscure-glazed and can’t be opened.
  • On any designated land, a two-storey extension is not covered by permitted development rights.
  • The exterior of the extension must use similar-looking materials to those of the property.

Side extension rules

  • A single-storey side extension must not exceed four metres in height and cannot have a width of more than half of the original property.
  • Side extensions are not permitted on designated land.

Rear extension rules

  • A single-storey rear extension will not go beyond the rear wall of the original property by no more than four metres.
  • A single-storey extension to the rear can be no more than four metres.

Terraced & Semi Detached House Extension Rules 2023

Permitted Development / Prior Approval

  • Under permitted development for a terrace or semi-detached home, you have the rights to extend by up to 3m without the need for planning permission!
  • For this you will need to apply for a lawful development certificate, which can be done either before or after construction, however we recommend the prior as it is always good to be sure that what you are building falls under the category. This will be necessary if you intend to sell the property at a later date, within 4 years of the building work completing.
  • There are specific rules to follow for permitted development projects, which is why it is always important to consult an experienced architect to ensure your projects success.

Householder/Full Planning Permission

  • If your property is within a conservation area, or if you are looking for a more unique extension with materials that differ from the original building, you will need to apply for planning permission for your extension.
  • Terraced & Semi-detached house extension rules under a householder application differ from council to council, but as a general rule of thumb you should not infringe upon the 45 degree rules – a line drawn at a 45 degree angle from your neighbours closest inhabitable space, i.e. a kitchen, living space or bedroom, as to not infringe upon their outlook and access to light.

Detached House Extension Rules 2023

Permitted Development / Prior Approval

  • Under permitted development for a detached house, you can extend up to 4m under permitted development, and up to 8m under the larger home extensions scheme / prior approval.
  • As above, many other factors need to be considered, therefore it is always good to speak with an experienced architect to ensure your proposal meets all of the house extension rules 2023.

Householder/Full Planning Permission

  • As above, if you live in a conservation area or other designated land, if your building is listed by heritage England, or if you are looking for a more unique extension, you will need to apply for planning permission from your local planning authority.
  • For a detached house, house extension rules 2023 are much more lenient, especially if your property sits on a large plot with generous space between neighbouring properties.
  • However, it is always important to check with an experienced architect, who will know exactly where to find the relevant council guidance to ensure that your project does not exceed the recommended allowances for detached house extension rules!

    Permitted Development Rules 2023 – How far can you extend without planning permission UK

    These are what are known as permitted development allowances. They only apply to houses. Flats, other buildings and maisonettes are not included. It is important to check with a Local Planning Authority to see if the permitted development rights will apply to your extension. This is to make sure that there are no other constraints to think about.

    You may be wondering how far you can extend without planning permission 2023, and this will vary depending on the type of house you own. Permitted development changes came into place in 2020 as a result of the ongoing pandemic and many homeowners needing additional space to go about their daily routine. This would also boost the UK economy, by giving work to contractors and service companies throughout an otherwise challenging period of time.

    The changes implemented the larger home extension scheme, otherwise known as prior approval. This is a 28 day application to determine, via your neighbours non-objection, how far can you extend without planning permission. For example, for a terrace or semi-detached home, you can extend up to 6m as opposed to the original 3m, and for a detached property you can extend up to 8m as opposed to the original 4m.

    With this in mind, however, you must be careful as many factors contribute to your extension falling under PD, such as the height, ground level, raised platforms, the original, as-built property footprint and boundary wall placement. If you are unsure or need help understanding how far you can extend without planning permission in 2023, contact our specialist advisors today.

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    Table of Contents

    Last updated | 27 Feb. 2023

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    What to know before building an extension? ›

    What to consider before you start your extension
    • Will your extension plans add value? ...
    • Permitted development and planning permission. ...
    • Building regulations. ...
    • Your home insurance cover. ...
    • Leaseholders. ...
    • Your neighbours. ...
    • Party Wall Agreement. ...
    • Finding an architect.

    What are the stages of building an extension? ›

    The 6 stages of an extension and how long it will take
    • Surveying.
    • Design.
    • Planning.
    • Building regulations.
    • Tender process.
    • Building.

    How much can I extend my house? ›

    1. Under the relaxed rules, you can extend up to eight metres for detached houses and six metres for all other houses. Please note that for these larger extensions (beyond four and three metres respectively) you will need to give notification under the Neighbour Consultation Scheme.

    What is the 45 degree rule? ›

    In normal circumstances, no development should intrude over a line drawn at an angle of 45° in the horizontal plane from the midpoint of the nearest window of a habitable room (includes kitchens but not for example bathrooms, w.c.'s, en-suites, landings, utility rooms or garages.)

    What is the first thing to do when building an extension? ›

    A Step By Step Guide To Adding An Extension Onto Your Home
    1. Step One: Do Your Research. ...
    2. Step Two: Planning Permission. ...
    3. Step Three: Building Regulations. ...
    4. Step Four: Find an Architect. ...
    5. Step Five: Find a Builder. ...
    6. Step Six: Move Out.
    Jul 17, 2017

    What can go wrong with house extension? ›

    The biggest mistakes to avoid when designing an extension, and how to get it right
    • Not knowing what you'll use the extension for. ...
    • Neglecting how you want to feel in the space. ...
    • Not having enough natural light. ...
    • Having too much natural light! ...
    • Not creating a seamless connection with the existing house.

    What time of year is best to do an extension? ›

    Summer is the most popular tie of year to build an extension just because of how practical it is when it comes to having work done. There will be no cold spells in the house from walls or roofing being altered, and that's the most important thing for most people who are on the fence about the build.

    How long does a house extension take? ›

    Depending on the size and scope of your extension, the length of time usually varies anywhere between 7 and 15 months (sometimes a lot longer). This is because building an extension involves a lot of different processes and professionals, plus a lot of unpredictable factors.

    What are 3 extension strategies? ›

    Extension strategies include rebranding, price discounting and seeking new markets. Rebranding is the creation of a new look and feel for an established product in order to differentiate the product from its competitors.

    What is the cheapest way to extend a house? ›

    Single storey extensions are often the cheapest and most viable option, and could totally transform a small home, bringing in light, extra living space and opening up the house to the garden.

    Is it cheaper to extend a house up or out? ›

    Building up is always the least expensive option for increasing your home's square-footage because it requires less material and labor. For example, if you have 1,000 sq. feet on the main level and want to add 1,000 sq. feet as a second floor, all you have to do is add more wood and framing labor.

    What are the rules on extensions? ›

    An Extension will require Full Planning Permission where:
    • It is to cover more than 50% of land around the original house (as it was first built or as it stood on 01 July 1948)
    • It is to be forward of the principal elevation or side elevation fronting a highway.

    What are permitted development rules 2023? ›

    PD Rules allow a maximum height of 4m for single storey rear extensions if dual pitched, with a maximum height of 3m at the eaves. If a flat roof, this is limited to 3m across the whole extension.

    Can my Neighbour stop my extension? ›

    In answer to the question – can my neighbour stop me building my extension? The answer is no, they cannot. They can request additional details which (1) makes things more expensive for you and (2) takes additional time. They cannot stop you from building.

    How deep do I need to dig foundations for an extension? ›

    It is important then to take foundations to a depth that is not affected by changes in available moisture. If there are no trees within 32m, foundations in clay are normally a minimum 1.0m deep. The closer a tree to the building the more that the deepest roots affect the moisture in the clay supporting the building.

    Where do I start if I want to extend my house? ›

    Council websites are a good starting point and you can also ask a building professional, such as an Architect, for advice. Permission can be granted subject to certain conditions or refused. Council planners consider issues such as impact on neighbours, character of the area and road safety.

    Do I need an architect for an extension? ›

    There is no law saying you have to employ an architect. It is up to you. Some people successfully undertake quite major works – including whole house refurbishments and extensions without an architect. Others employ one for comparatively minor jobs, such as redoing a bathroom or redesigning a kitchen.

    How much does a house extension cost? ›

    The cost of a home extension will vary depending on several factors, such as the size and location of the extension, the type of materials used, and the amount of work required. In general, you can expect to pay anywhere from €1,900 to €3,400 per sqm. The final cost depends on your circumstances.

    What makes an extension expensive? ›

    Building a house extension is often cheaper than upsizing and avoids the stress of moving. London extensions do however have a cost premium when compared to the rest of the UK. This is due to higher labour and material costs, and the difficulties of compact construction sites.

    How do you decide if an extension is worth it? ›

    If a home extension gives you the right amount of space in the right location and allows you to live your life as you choose, then we think it's definitely 'worth it'. Though the financial investment can be significant, the return on the investment is often greater still. “I love, love love, my house.”

    How far can I extend my house without permission? ›

    You can add a home extension or conservatory up to six metres, or eight metres if your home is detached, without needing to apply for planning permission.

    How much should I pay for extension plans? ›

    We could tell you that the average cost of an extension in London is generally estimated to be somewhere around £40,000 - £50,000. But that won't tell you the cost of extending your home. For that, you'll need to think about exactly what it is that you're planning to do.

    What month is best to start an extension? ›

    Ideally, you should aim for the construction of your extension to commence in March or April, when there's little chance of the ground being too frozen to dig, or the air being too cold for brickwork.

    How can I save money when building an extension? ›

    Choose a simple design

    Keep the design of your extension simple. Stick to square and rectangular shape layouts. Avoid odd shapes if you want to cut costs. Curves and L-shapes are expensive to build.

    Can you live in a house while getting an extension? ›

    It is possible to live on site throughout a house extension, but aside from all the dust and mess, you may end up slowing down progress as the builders attempt to work around your life.

    How long to lay foundations for an extension? ›

    The first step in the process is for the site to be prepared. It usually takes around 2 weeks to dig out the footings and prepare the foundations, and then a further 2 weeks to install the damp course and any drains that are needed around the extension.

    How long does it take for an architect to draw up plans for extension? ›

    Summary: what to expect from your architect during the planning stage. Things can happen more speedily than the above example, but in our experience, it can take up to a year to design and plan a full house renovation/extension project, with a further estimated 6-8 months build time after that.

    What are the commonly used extension methods? ›

    They are (a) the individual method, in which the agent deals with farmers on a one-to-one basis; and (b) the group method, in which the agent brings the farmers together in one form or another in order to undertake his extension work.

    What is an example of extension? ›

    Flexion And Extension Movement Examples

    Extension would be the straightening of the arm back to starting position, increasing the length and angle between the joint.

    What happens during the decline stage? ›

    the final stage of the product life cycle (after introductory stage, growth stage and maturity stage) when sales are dropping because the original need and want have diminished or because another product innovation has been introduced.

    What is the most expensive part of an extension? ›

    In fact, the most expensive elements of an extension are the roofing and foundation. Therefore, by building up, you can gain more space with only a marginal increase in price.

    How do people afford to extend their homes? ›

    A home improvement loan is one option for funding a house extension. A home improvement loan offers the flexibility to fit repayments around big life changes. This type of loan type is unsecured, so you don't borrow against your property.

    What extensions add the most value to a home? ›

    Best extensions to add value to your home
    • Loft conversion – average value add: up to 20%
    • Double-storey extension – average value add: up to 12%
    • Conservatory – average value add: 5-7%
    • Garage conversion – average value add: 10-20%

    What is the cheapest way to build an addition? ›

    A bump-out is a less-expensive option that allows you to add space to your home without having to conduct any foundation work. A bump-out hangs over the existing edge of the house and can make an existing room feel more spacious. Bump-outs can serve different purposes based on what rooms you choose to put them in.

    How much does it cost to add a bedroom and bathroom? ›

    The cost of adding a master bedroom and bathroom to your home can vary. Most homeowners spend around $62,500 on this project, but the cost of this addition can range from as low as $25,000 to as high as $100,000.

    Is it worth it to expand a house? ›

    Great High Cost-Value Ratio

    It is typically cheaper to build an addition than to buy or build a new home that equals the space of your existing house plus an addition. At the very least, the closing costs involved with selling your old house and buying the new house would push this option over the top.

    What should you not put in extensions? ›

    Using Harsh Products

    Shampoos containing sulfates, parabens and alcohol are awful for your extensions. Use moisturizing products that are free of sulfates and parabens are better for both, your hair and extensions and protect them against unnecessary damage.

    What to expect when getting extensions? ›

    Extensions require a bit of extra care and attention. If you opt for a permanent solution, like tapes or hot/cold bonded extensions, you'll need to factor in some extra time to wash, dry, and style your new hair. Don't make a habit of leaving extensions wet, since they can start to slip or get sticky.

    How many years do extensions last? ›

    Even the best hair extensions have to replaced, especially if you want to avoid sad, scraggly strands. How often you have to replace extensions comes down to which kind you have: Fusion extensions (every 3-4 months), tape-in hair extensions (4-8 weeks), or hand-tied extensions (3-4 months).

    Will 2023 be a better time to build a house? ›

    Based on what we're seeing, our team of experts here at Heartland Builders thinks that 2023 will be a good time to build your custom forever home, despite rising costs and interest rates.

    What are the new rules for building? ›

    Most residential properties in Auckland's urban areas are proposed to come under one of three zones:
    • Terrace Housing and Apartment Buildings Zone (now allowing for buildings of six storeys or more)
    • Mixed Housing Urban Zone (now allowing for three dwellings of up to three storeys)
    Jan 9, 2023

    What are the new permitted development rules? ›

    Permitted development rights are essentially a scheme, created by the government, that allows you to extend/renovate your home without the need for a full planning application. For some homes in England, this scheme expanded last year to include bigger projects and more options for home improvement.

    Can my Neighbour take down my fence to build an extension? ›

    Paula Higgins, chief executive of HomeOwners Alliance, told The Sun: "If you own the fence and it is on your property, neighbours have no right to take it down even if they have been granted planning permission. "You should also check whether there needs to be a Party Wall Agreement in place."

    How far can I extend my property? ›

    Permitted development rights

    Width: the width must be less than 50% of the width of the existing house. Length: the max length of rear extensions is 3m for terraced or semi-detached houses, up to 4m for detached houses. Height: for 2 storey extensions, the height must not exceed the height of the existing house eaves.

    What are the 3 types of foundations? ›

    There are three main foundation types: full basement, crawl space and concrete slab.

    What are the 4 types of foundation? ›

    There are five main foundation types and a handful of important variations.
    • Basement Foundation. ...
    • Crawlspace Stem Walls. ...
    • Concrete Slab Foundations. ...
    • Wood Foundations. ...
    • Pier and Beam Foundations.
    Jul 2, 2020

    What size extension can you build without permission? ›

    You can add a home extension or conservatory up to six metres, or eight metres if your home is detached, without needing to apply for planning permission. There's very little standing in the way between you and your dream home!

    What questions should I ask a builder for an extension? ›

    Expert Advice - Questions To Ask Your Builder
    • Can you give me references? ...
    • Are you insured? ...
    • Do you use subcontractors? ...
    • Will you project manage the work? ...
    • How often should we meet? ...
    • Do you offer a guarantee? ...
    • How many projects do you work on at any one time?
    Nov 27, 2022

    What is the most cost effective way to build an extension? ›

    If you want to build an extension fairly cheaply then opt for concrete blockwork. It's a system most builders know well, too. If you have the skills and time, a blockwork extension on a DIY basis will be the cheapest way of adding an extension. Timber frame extensions are a popular choice, too.

    Can you build an extension without foundations? ›

    You will need foundations for a conservatory or extension, and these base systems come in different materials such as timber, concrete and steel.

    Do you have to notify Neighbours permission for extension? ›

    The technical term for this is called serving notice. In short if you want to make your home bigger and are attached to (or are in close proximity to) another property, you will most likely need to notify the neighbour(s) about your extension.

    Do I need construction drawings for an extension? ›

    One of those vital steps is the drawing and design stage. Getting your house extension plans right is an absolute necessity for your dream extension to become a reality. To achieve this you'll need the proper architectural drawings and knowledge and the right guidance from skilled professionals.

    How do you keep cost down when building an extension? ›

    30 Ways to Save Money on Your Home Extension Project
    1. 1) Plan the size of your extension carefully. ...
    2. 2) Types of extensions. ...
    3. 3) Designing your extension. ...
    4. 4) Fixed-price design extensions. ...
    5. 5) Get detailed drawings done. ...
    6. 6) Extension construction methods. ...
    7. 7) Put robust contacts into place. ...
    8. 8) Seek multiple contractor quotes.
    Jun 10, 2021

    Who draws up plans for a house extension? ›

    A good architect, architectural technologist, or design and build company will help you choose the right materials and work with you to design an extension that will suit your needs best.

    What is the cheapest type of house extension? ›

    Single storey extensions are often the cheapest and most viable option, and could totally transform a small home, bringing in light, extra living space and opening up the house to the garden.

    How much do builders charge for extensions? ›

    All of the guideline prices listed below are for construction only, updated as of 2022. They do not include VAT or professional fees. House extension costs: Single storey – A single storey extension in London will usually cost between £2,200 and £3,300 per sqm (£200 and £300 per square foot).


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