What is a small extension?

Small extensions can be used for any number of purposes and are a budget-friendly way to expand the space inside your home whilst also increasing its value. Many small extensions are built to take advantage of otherwise redundant outside space that can be put to better use.

Creating an additional room can connect your garden with your interior, provide a quiet relaxation space, create a home office away from the busier living areas of your home, and can be used to bring more natural light into the space.

Size is one of the biggest cost factors in budgeting for an extension, and it is worth noting that the cost per square metre for a smaller extension does tend to be higher than for larger builds. This is because some aspects of larger build projects benefit from economies of scale the bigger the footprint, which are not available for small extensions.

What are the benefits of a small extension?

Building a small extension to your home can be a fairly cost-effective project, but can increase the value of your home quite significantly. For example, if you live in a period property with a small kitchen and extend outwards to create a larger space, your property will command a higher sales value than others in the area.

In urban areas where parking is at a premium, creating a small garage extension, lean-to, or off-road storage space can bring the value of your home up considerably.

Other benefits include access to natural light; in built-up areas, creating a small sunroom or conservatory with rooftop glazing can flood your ground floor with sunlight, and change the dynamic of your living space.

The flexibility of a small extension means that it can serve any purpose, from increasing the size of an existing room, creating a new separate utility, office or storage area, or making use of your outdoor space to maximise the floor plan of your property.

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What are small extensions used for?

A small extension is a uniquely flexible space, and can fit any purpose that will improve your living areas:

  • Playroom or sunroom
  • Conservatory or garden room
  • Lean-to for utilities or storage
  • Utility or pantry area
  • Garage or outdoor storage space
  • Connecting room to join two parts of your home together
  • Extension to increase the size of your ground floor
  • Adding a dining space to your kitchen area
  • Building an enclosed porch for security and weather protection for the front of your home
  • Creating a box dormer on your upper level to lift your ceiling height
  • Erecting a light well to bring natural light into a basement area

As you can see, there is no end to the options! A small extension can be built on any aspect of your home, from building up from your attic, adding a side return extension along the side of your property, building on garden space to the rear, or extending outwards with a bay window extension or similar project.

How much does a small conversion cost?

The cost of building a small extension starts from around £1,000 per square metre, and increases from there. More complicated designs, sites that are difficult to access and bespoke extensions can cost from £2,000 per square metre and above.

Deciding on a budget for your small extension depends on several factors:

  • How much land you have to build on
  • What purpose your new extension will serve
  • Whether any outdoor works are required, such as removing trees and shrubs
  • If your new extension is an addition to an existing room and will require internal walls to be removed
  • What materials and finishes you would like inside and out
  • The amount of glazing required, and whether this is a standard size or bespoke

There are plenty of options to add a cost-effective extension to your home to free up space inside and make use of empty outdoor space. Pre-fabricated shells are the most cost-effective option, but your choice of build will depend on all of the above factors.

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What are the important factors to consider when designing a small extension?

Choosing a small extension is an exciting time, and working out the best way to make the best use of this space for your family or property. To ensure that your project runs on time and budget, there are many different factors to consider:

  • Do you need planning permission? For a vertical small extension such as a box dormer, you will certainly need to make a formal application, so allow plenty of time for this process.
  • Do you need a Party Wall Agreement? If you are building next to common boundaries between your property and your neighbours, you will need a formal agreement in place and may need to commission a Party Wall Surveyor to create this for you.
  • How much land do you want to build on? Creating a side return is a great way to make use of empty space, but if you plan to extend outwards towards the rear of your property remember that every extra inch you build on will remove space from your garden.
  • Where does natural light hit your home, and where would an extension be best placed to take advantage of that?

In urban areas where parking is at a premium, creating a small garage extension, lean-to, or off-road storage space can bring the value of your home up considerably.

Frequently asked questions

Do I need planning permission for a small extension?

Whether or not you require planning permission will depend on the design, size and location of your small extension. Lots of small extensions do not require planning permission since they fall within the requirements of permitted development (PD).

Remember that, even if you do not require planning permission, you will need to comply with Building Regulations. This means submitting notice to your local authority or building control department. An inspector will visit the site at specific intervals to ensure that the build is constructed safely.

You can also choose to apply for a Lawful Development Certificate, which is available from your local planning authority for £103 (50% of the planning permission fee). This certificate verifies that your extension falls under PD, and is useful to have should any future queries arise, particularly when looking to sell your home.

PD depends on criteria such as not extending more than 4 metres high, not extending outwards at the front aspect beyond the original property, and not building close to party walls or common land, in which case planning and/or a Party Wall Agreement will be required.

We advise contacting your local council for advice if you are in any doubt to ensure that any requisite permission is in place before work begins.

How long does it take to build a small extension?

The build itself for a small extension typically takes around three months, although can be quicker for a simple design or an easy construction process. Larger extensions can take upwards of six months, so a small extension is a much faster build project.

Remember that any permissions, applications or agreements can take just as long as the build time itself, so your total project timescale should be at least six months to give sufficient time for those processes to be completed before the build begins.

How should I choose a contractor for my small extension?

Choosing the right contractor is dependant on price, availability and quality. Our advice is to choose a contractor from a registered trade body who holds accreditations and is a respected tradesperson with a track record of completing successful projects.

To ensure that you are not paying over the odds for your small extension, it is always advisable to obtain at least three quotations for comparison. If you have identified a contractor that you would like to work with, this can also be a negotiating point to agreeing to a price that you are comfortable with.

Recommendations are always useful since you can obtain references about their standard of work, or ask to view their portfolio to get an idea about what sort of build projects they specialise in.

What should I look out for in my small extension quote?

Bear VAT in mind when comparing prices – if your contractor is VAT registered and does not state that the price is VAT inclusive, your final bill will be 20% higher than the quotation. A VAT-registered contractor should always display their VAT number on their paperwork.

A fixed project price is always preferable to paying a day rate since this ensures that it is in both yours and your contractors’ interests to finish the work on time. Day rates can be a recipe for disaster so we would only suggest working on a day rate if you have any additional jobs outside of the original agreed scope of work that you would like your contractor to undertake.

Your contract should always state exactly what works are included, what materials the contractor will provide, and any limitations where you will require extra tradespeople; such as gas fittings, electricity points or decorating.

Agree to the stages of payment in advance; this could include a deposit, a partial payment at a particular stage, and then a final payment on successful completion. Make sure that snagging is included so that you have the opportunity to rectify any niggles or problems before the job is considered complete and the final balance has been paid.

Rich Crossley
Having spent 30 years working all over the world for top-tier investment banks, I’ve owned and developed houses all over the world – Europe, the US and Asia. I’m now based back in the UK and involved in the property industry – oh, and I’m a keen DIY enthusiast!
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