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​Clever tricks to save money on your home extension

Johannes van Graan Johannes van Graan
Tetris, Park Road Modern houses by MZO TARR Architects Modern
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Dreaming of a bigger bathroom? How about finally getting that spacious art studio or dining room you’ve always wanted?

Adding an extension to one’s home is definitely cause for celebration – that is, if there is any money left over afterwards to buy some decent champagne. Because like all things in life, an extension costs money – and quite a lot, depending on the specifics.

But, life has indeed treated us to numerous ways in which we can make lemonade, and that extension is no exception. There are always corners to be cut, and if you’re clever, some pretty huge shortcuts can be made without compromising on any end-result quality.

So, to keep that extension dream of yours alive and kicking, let’s see how you can save some pretty pennies and stay in control of your budget…


Extension in Sheen, SW14 Modern houses by TOTUS Modern

Extension in Sheen, SW14


Keep It Simple, Stupid – a rectangular or square footprint with a simple pitched roof will be the cheapest. To save even more costs, avoid any products that have to be made to order; rather opt for materials that are readily available and easy to use (such as concrete for the sub-floor and walls; brick, render or timber cladding; and a softwood timber roof structure). 

Try roof lights instead of dormer windows and interlocking concrete tiles for covering the roof.

If at all possible, don’t build near trees or drains and sewers, as complicated groundwork can also affect those costs.

2. Save money with a DIY extension

Courtyard House - East Dulwich Modern balcony, veranda & terrace by Designcubed Modern

Courtyard House — East Dulwich


Labour costs represent about 50 – 65% of the outlay for a typical extension, which means a great saving if you can manage some of the work yourself. 

The easiest tasks to take on are labouring, decorating and landscaping, followed by some ‘second fix’ trades like kitchen- and bathroom fitting, tiling, and fixing coving and skirting boards. 

However, never take on work you don’t have the time or skills for. Read up in advance and never rush, as poor workmanship and wasted materials can make DIY a false economy. Rather hire an expert for areas where the results will be on display all the time, such as the bricklaying and plastering.

3. Project-manage the extension

Terrace Mediterranean style balcony, veranda & terrace by TG Studio Mediterranean
TG Studio


TG Studio

A builder will add approximately 15 – 25% onto the total cost of labour and materials for managing the project – which can be cut if you were to take on the responsibility of building contractor yourself. 

This will mean liaising with your designer/architect and your local authority’s building control department, finding and hiring tradespeople, directing the work and supplying all of the necessary materials, etc. Although very time-consuming, it can be quite rewarding – but bear in mind that you will need time and flexibility, as well as confidence, management skills, and some knowledge of construction to pull this off successfully. 

The job may take longer to complete overall, but the savings can be enormous.

4. Save on VAT

Most extension work will attract VAT at 20% on labour and materials, but if you use self-employed tradespeople who each turn over less than the threshold for VAT registration, you will not be charged this tax, which will save you labour costs. 

Second-hand materials sold by private individuals online will also be free of VAT.

Certain types of work attract reduced-rate VAT in any case, such as upgrading insulation and extending a building that’s been vacant for two years, for example.

5. Keep your neighbours in the loop

Building on or near the boundary of a neighbour means that your extension will need to comply with the Party Wall Act (England & Wales) 1996. If a party wall settlement is required, it will cost around £700 per neighbour; possibly more if they use their own independent surveyors.

You need to notify your neighbours in writing about your extension plans eight weeks before work starts. If you can get them to reply in writing that they have no objections, you can avoid using a surveyor to arrange a party wall settlement and save on more fees.

6. Pick your professionals wisely

Certain designers know how to keep the costs down, while others strive for producing complicated (although beautiful) plans that are quite costly to build. 

For a simple, low-cost build, find an architect, architectural technician, chartered surveyor or structural engineer who will produce planning and Building Regulations drawings for a fixed, all-in price. It will be worth the effort to search for a track record in designing low-cost projects.

7. Avoid the swindlers

Rural extension, Dorset, UK Modern living room by Southpoint Modern

Like in any trade, the architectural- and design industries also have their fair share of tricksters – people who vastly underestimate costs, either through incompetence or to secure a job; those who charge more money for changes or ‘extras’; and the ones who demand some or all of the money up front, leaving you with no comeback if they fail to produce acceptable work. 

Before deciding on someone, always ask for references, and be sure to check them out. And only pay for work that has been completed and that you are happy with.

Never pay for materials in advance. If a builder does not want to supply materials, rather purchase them yourself.

8. Measure twice, but cut once

Golders Green, Barnet NW11, London | House extension: modern  by GOAStudio | London residential architecture, Modern
GOAStudio | London residential architecture

Golders Green, Barnet NW11, London | House extension

GOAStudio | London residential architecture

An accurate and scaled plan is crucial, and will definitely help ensure correct results, such as wiring and plumbing in the right places, and doors that swing in the most space-efficient direction. 

Measure everything onsite rather than off your plans to help reduce wastage. And once you have made up your mind, stick to it; changes always incur extra costs, often in ways that don’t reveal themselves until much later.

9. The three R’s

Reuse, recycle, and repair.

Existing materials can be reused or sold rather than tossed away. Old floorboards, doors, kitchen units, etc. can all be cleaned up and given new finishes. Sell or trade what you can’t use. 

Remember that buying salvaged materials can be a lot cheaper than purchasing new ones; they also introduce instant character. Some second-hand items that offer good value include roof tiles, bricks, internal doors, timber floorboards, and fireplaces. 

Reducing wastage will also lessen costs for skip hire and disposal. And remember that, as a private individual, you can dispose of waste in your local council tip for free.

10. Negotiate for discounts

Find out where those in the trade buy their materials and aim to get the same wholesale/trade prices. Always negotiate and see if there is any discount for paying in cash – just ensure you get a receipt. 

Bulk-buy from a single supplier for a further discount and ask about reduced delivery costs. However, getting the best deal will often mean moving away from the big brand names and finding equivalents without the price premium. If you are clever, however, you can save on price without compromising quality.

homify hint: Stick with the basic specifications to keep those costs down: go for radiator-based central heating, carpets for floors, and standard white sanitary ware.

Careful with that culinary extension, as there might be: Kitchen renovation costs you may have overlooked.

Got any more money-saving tips for building?
Whitton Drive by GK Architects Ltd Modern

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