​Clever tricks to save money on your home extension

Tetris, Park Road, MZO TARR Architects MZO TARR Architects Modern houses
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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 with these DIY extension ideas…


1. KISS

Keep It Simple, Stupid – yes, even when working on a DIY extension. 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

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

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

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

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.

Bonus building tips for your next DIY extension: Remember storage

Storage space is crucial, even while you’re still building whatever it is you want to build (in this case, a new extension). Because where do you plan on storing all the heavy materials needed to build your extension? Are they secure? Will they block your driveway or intrude on your neighbour’s space? Consider this early in the planning stage while you’re still mulling over DIY extension ideas. 


Bonus building tips for your next DIY extension: Professional plans

Your DIY extension is already off to a bad start if your design plans don’t clearly detail all the elements that need to be included – right down to the window- and door sizes. Remember that the more detail there is in the drawings and plans, the smaller the chance of your project veering off course. 

Bonus building tips for your next DIY extension: Agree on prices

When an invoice arrives with higher costs than expected, the blame usually lies with one of two people: the client (you), for not being clear about what they want and how much they will pay for it; and the professional/tradesperson for not effectively communicating the rising expenses. Help your DIY extension project proceed and conclude without this headache by keeping all communication lines open between you and your professional (whether it’s an Architect, Interior Designer/Decorator, Painter, Carpenter… ) of choice.  

You know what you need? These 26 standout DIY tips!  


Got any more money-saving tips for building a DIY extension?

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