Where to spend and save on a home extension

Thinking of extending your home to boost its value and give you more space? Find out where it’s worth investing – and where you can make savings – to get the best results for your budget

TODO alt text

This detached bungalow in Lancaster was extended and modernised by SDA Architecture to bring it up to date. A simple footprint and timber cladding kept the extension cost to £70,000

1. Get the right team

SPEND: Find the right designer

The services of an architect or architectural technician can prove invaluable. They’ll suggest design ideas you’ve not considered and factor in everything from improving flow, to maximising light, and creating a space that’s both practical and beautiful. When looking through designers’ websites, spot if they have won any awards for their work, and whether they have experience of similar projects. To find designers in your area, search the Royal Institute of British Architects database or Chartered Institute of Architectural Technologists.

SPEND: Don’t skimp on labour

‘A bad trader will probably damage something when working, and end up costing you more than a professional who quoted you a more accurate cost from the outset,’ warns Dominik Wielgus, managing director of Black Oak Builders. ‘Shop around, find a reputable company and always check their references. You might need to wait for them to become available, but the start date and the price are not the most important things – quality and service is.’

 ‘The cheapest builder is not always the best. Sometimes it is worth investing more to get what you want’ – Charlie Borthwick, of Cue & Co London

SPEND: Protect your project

Most home insurance policies don’t cover the property during building work, so you’ll need to find a specialist provider. Ensure you’re covered for any damage to the existing or new parts of the property, any impact on your neighbours, any plant or equipment hire, and public liability in case anybody is injured on your site. Try Build-Zone or Self-Build Zone.

SAVE: Employ some trades directly

‘If you send your design out to a builder and ask him to price it, he will include everything, right up to employing decorators on your behalf,’ advises renovation expert Jason Orme. ‘Even if you can’t handle the painting, you can employ someone directly to do it – saving you the main contractor’s fees on that element. Always consider how much of the recruitment of trades you can be responsible for.’

SAVE: Get the timings right

If you are super-organised and have the time to commit to the project, you could save between seven and 10 per cent of the build cost by acting as your own project manager — but make sure you plan ahead. ‘Building work can go wrong very fast and, unless you’re confident you can project-manage yourself, it may be worth employing a sub-contractor to oversee the work for you. A site with no one working on it is costly, so materials need to arrive in plenty of time,’ advises Steven Way, practice principal at Collier Stevens Chartered Surveyors.

It plans to involve a kitchen designer from the start of your extension project

It’s crucial to make sure materials arrive on site when needed – otherwise you’ll be paying contractors who have nothing to do. This Benchmarx kitchen costs from £3,069 for eight units

2. Get the best design

SAVE: Work out how much it’s worth spending

Ask a local estate agent how much your planned extension might add to your home’s asking price. Comparing the value you are adding to your property to the cost of building the extension and fitting it out will allow you to make sure that you’re not out of pocket after the project. As a rule, the more floor space you add, the more value you add. Of course, the bigger you go, the more it costs, so weigh up what you are trying to achieve – a higher property value, lots more space, or perhaps just small additions to make life more comfortable?

SAVE: Go for a cost-effective layout

The simpler your extension’s design, the cheaper it’s likely to be – and that includes interior fittings, such as the kitchen. ‘The layout of your new extension will affect your budget,’ says designer Charlie Borthwick. ‘Complex configurations will be more costly, whereas a simple, rectangular space will save money.’ Check out these ways to cut the cost of your extension.

SAVE: Consider whether you could remodel instead

Most British garages aren’t actually used for car storage, and if you live in an area where on-street parking is accessible, they are a wasted asset. For around £10,000 upwards, you could convert your garage into useful – and valuable – extra living or utility space. Want to be sure it’s the right thing to do? Ask a trusted local estate agent first if converting yours would have a negative or positive impact on your home’s value.

In an open plan space it pays to consider how the kitchen flows into the rest of the room

Think carefully about how to integrate your kitchen into the existing space. The polished concrete flooring and wooden cabinets tie these old and new spaces together. Kitchens from £30,000, Whafside

SAVE: Plan the interior from the start

Spending time planning the smallest of details can save you money further down the line. By specifying everything from light fittings and socket locations to flooring and wall colours at the outset, you’ll save money on the cost of making alterations at a later stage.

SAVE: Stick to the agreed design

‘It’s important to stick to the plan and design you’ve agreed, as any changes will cost money,’ says surveyor Steven Way. ‘Have a proper building contract with an itemised budget and an order of works in place, which will help save you money in the long run.’

SAVE: Comply with building Regulations

It’s vital that everything that goes into your build is compliant to building regulations and planning permission, or it may be your responsibility to replace, upgrade or even remove it, at your own expense. Although a good builder or architect will ensure the materials you are using do comply and are up to standard, it does pay to do your own research when it comes to glazing, insulation, cladding and fire safety.

SPEND: Get room temperatures right

If you’re having large expanses of glazing, seriously consider air conditioning, as these rooms can become very hot in summer. Make sure, too, that it’s well insulated for colder months. And consider whether you want underfloor heating or radiators, which will need to be carefully positioned. 

It s worth investing in quality glazing even on a budget extension

This contemporary conservatory has a solid roof and high-thermal-performance glazing, which means the dining room feels light and airy year-round, and warm even in the middle of winter. Conservatories from The Caulfield Company start from £25,000

SPEND: Hide the extension’s structure

If you are knocking down walls, the cheapest – and easiest – route is to place supporting steel beams under the joists of the floor above. However, this means they will be visible in your finished ceiling, creating an interruption in levels. ‘Avoid this if you can afford to,’ says interior designer Nicola Steer. ‘Otherwise, you will have gone to the trouble of creating an open-plan space, but the impact will be spoilt by this visual division. It’s better to go to the extra expense of putting the beams up into the depth of the floor above to create a level ceiling. You can cut back the budget on fittings that can be updated later, whereas structural works can’t.’

SPEND: Link old and new

Don’t just consider the layout of your new space – consider, too, how the transition from the original part of the house to the new extension will work. ‘An extension can give you a stunning new space that’s used regularly, while existing adjacent rooms are suddenly relegated to being underused,’ says estate agent Jeremy Leaf. ‘It’s important that you work out how existing parts of the house will be utilised.’

SPEND: Get the exterior right

Getting the outside of your extension absolutely right is a must, even if that means cutting back on your interior design budget. Should it mimic your original home’s exterior, or contrast with it? The answer may be down to what the local planning authority feels is most appropriate – but it’s usually better to go for one or the other, rather than a pastiche.

3. Choose the right materials

SAVE: Consider construction methods

The two main options for building your extension are timber frame or blockwork. Costing and comparing these two methods is hard to do, except on a case-by-case basis. Talk to your builder about which might be more cost-effective for you to take on.

SAVE: Factor in your location

Using local materials could save you money on transport costs. ‘Where your home is situated is paramount to the design of your extension,’ advises architectural director Simon Lewis-Pierpoint. ‘The best are those sympathetic to, or contrast with, their surroundings.’

SAVE: Do your research

Plan your kitchen layout from the start of your extension planning

‘If yours is to be a large, open-plan kitchen-dining-living extension, make sure your budget allows for glazed doors, either bi-fold or sliding, that open to the garden,’ says Jonathan Stewart, owner of luxury kitchen company Wharfside. The same goes for windows – getting the size and positioning of these right is worth the time and money spent. And don’t forget rooflights – these are a good way to bring light into the depths of a room. If you’re putting in sliding or folding doors, the less frame you see, the pricier they usually become.

SPEND: Factor in technology

Make sure you put in all the cabling that you think you will need now and in the future. You don’t have to install the hardware immediately, but if you put the cabling in now, you will have the flexibility to add it in later. For example, will you ever want a TV or music in a certain room – if not now, then in a few years? The cabling can be fixed and hidden in the walls so you can access them at a future date.’ Consider sockets with USB charging points, surround-sound systems, and smart home security.

Click here to get a comprehensive extension cost calculation using our free extension cost calculator