top of page

Are you thinking of having a rear house extension added to your property.



An extension to your property is one of the most effective home improvements you can make. Yet while some homeowners might be blessed with insider trade knowledge, many people looking to extend their houses aren’t familiar with construction, architecture, or property design.

Without some solid advice – and a few relevant tips to get you started – it can be easy to miss something, make a mistake, or end up spending far more than you originally intended.

We have worked with a lot of architects over the years, on a wide and diverse range of projects. If there’s one thing we’ve learned, it’s that when designing and planning a house extension, a lot of questions come up – particularly in the early stages of the process.

So, to provide you with some key house extension tips, we’ve answered some of the more frequent questions that come up

during the planning process, and provided some handy tips and advice for you whilst you consider your project.


What are the different types of house extensions?

The term ‘house extension’ simply refers to any structure that’s added to the original building. This can be a loft extension, basement extension, a kitchen, a living space, or even a new bedroom. Extensions can be made from a variety of materials: from simple modular house extensions to brick & block to more expensive, luxury designs, such as those including structural glass .

House extensions are usually one or two storeys high, and include everything from conservatories and garage roof extensions to multi-storey annexes, featuring their own kitchenettes, bedrooms, and bathrooms.

Will I need planning permission for my house extension?

The honest answer is that it depends, but usually no, you won’t need planning permission for your house extension. Most properties benefit from what’s called ‘permitted development’, which basically means that you can extend the original building (which is as it stood in 1948) without applying for permission – provided you obey certain restrictions.

These include things like not extending above the height of the roof of the property, and limitations on how far your extension can project outwards, but they will depend on the type of property you own. The full list of permitted development criteria can be found here:-

Town Houses, Semi Detached Houses projecting up to 3m Out - do not require any planning and fall in line with permitted development.

Detached Houses, projecting unto 4m Out - do not require any planning and fall in line with permitted development

Both types of houses above can project double the permitted development with registering a proposed larger home extension application, which is relatively easy procedure and you can have permission granted within 21 days. If your not familiar with lodging this type of application let us do it for you and get it right first time. If you need drawings on existing and proposed elevations, we can also undertake this for you.

Do I need an architect for my house extension?

There’s a lot to be said about this, but we’ll try to keep it straightforward: the simpler you want to keep things with your extension, the less likely you’ll need to employ an architect. There’s no law requiring you to do so, and it’s all about personal preference.

If you simply want a basic modular house extension or, brick and mortar construction – or are planning something like a humble conservatory – then an architect is not necessary. If you have a grander vision for your space, or are looking for an expert to design something a little more special, then employing an architect is a sensible idea or let us come and survey

Are there restrictions on where to place toilets in a house extension?

Short answer: there used to be, but there aren’t any more. The Building Regulations (more on those further down) used to insist on a lobby space between a toilet and other rooms, but this is no longer the case.

You can place a toilet anywhere you like, providing there is ample room, that you include a wash basin and that you allow for sufficient ventilation. The same goes for showers, providing they meet minimum size requirements outlined in the Regulations. As a result, the main consideration when planning for a shower or toilet is the proximity to suitable plumbing, as this is one of the largest influences on price.

Do I need to tell my neighbours when I’m planning my house extension?

There is only a legal requirement to tell your neighbour about your extension plans if the work you intend to organise will impact the boundary between your two properties. In general though, it’s just common courtesy to inform your neighbours of any intended construction work.

The disruption caused by the noise of the building work is likely to have an impact on their lifestyle, at least for a short while, and it’s only right to give them the chance to prepare for this – particularly if they have young children, this is another plus sign of utilising a modular house extension, saving time, stress and mess on site.

It’s also worth noting that keeping the neighbours on side is a very sensible thing to do anyway, as it can make it less likely that they’ll take umbrage to your actions, and try to cause problems for the development, such as attempting to invoke their ‘right to light’ (if applicable – see below).

How high does the ceiling need to be in a house extension?

As is the case with toilet and shower rooms, there is no longer a minimum requirement specified in the Building Regulations as to the height of a ceiling in a house extensions. Your extension can’t be higher than the roof of your home, but other than that there isn’t any legally binding clause as to ceiling height. Your ceiling can be as high or low as you like.

With that in mind, it’s still important to be realistic about things. If your ceiling is impractically low, your extension won’t be a very nice room to inhabit; you don’t want your expensive new space to cause chronic back pain for anyone that walks into it. The normal ceiling height in the industry is 2.4m, around eight feet, and this is a good baseline when making your plans.

What are the building regulations for house extensions?

The Building Regulations are a set of guidelines and minimum standards, determined by government and enforced by local planning authorities, to ensure building work accommodates safety and health and factors. These can include everything from how a structure uses energy and water to its fire protection. The Regulations apply to any new builds, as well as to all extensions and alterations.

If you want an example: one regulation (the ominous ‘Part L’, that sounds rather like something out of the X-Files) relates to energy efficiency. The government has put in new requirements to raise the efficiency of all new buildings and structures by 40%, and so the amount of glass in a structure is now limited to 25% (Don’t worry, this doesn’t mean you can’t opt for one of the glass extensions we construct; you just have to factor in insulation elsewhere, or opt for something like low-e glass or triple glazing).

The full list of regulations is long, technical, but we handle all of this included in our fee.


How much will a house extension cost?

It might sound like a bit of a cop out, but the cost of your extension really does depend on a lot of things. It’s unrealistic to provide an average or benchmark cost of a house extension, as there are too many variables that impact price, but a very rough estimate would be to budget for £1500 – £2000 per m2 for all types of extensions including modular and bricks and mortar.

Can I claim VAT relief on my home extension?

You most likely can’t claim VAT relief for work carried out on your house extension project. If you’re using a contractor, then the standard rate of 20% almost always applies. There is sometimes an exception if you’re using independent tradespeople who aren’t VAT registered, in which case you’ll only need to pay VAT on materials used.

If your property is a listed building, and you’ve obtained permission to undertake work on your extension, then you’re in luck – listed buildings are zero-rated for VAT when it comes to improvements.

Will my house extension add value to my property?

One of the main reasons many people choose to extend a property is the prospect of increasing its value when they eventually decide to sell. It’s usually the case that adding more space to a property results in the value of said property increasing – particularly in London and the South East. One of the best ways to assess whether extending your home will increase its value is to speak to a local estate agent. They’ll be able to tell you the kinds of renovations that are popular in the local area, as well as offer a guideline to what the ceiling value of property in your street tends to be. If your home already approaches this, then it’s possible to ‘overextend’, and cap out the value of your property despite adding multiple new areas.

Do you have a project extension in mind? Let’s work together.

Want to discover more about the world of Modular House Extension? Get in touch. Visit our website and contact us to discuss a project. Or ask a question or get a price.



29 views0 comments


bottom of page