By taking on much of the work and design themselves, this home cost the Dawsons just £98,500

Taking on a large building project is daunting at the best of times, even for seasoned professionals. The majority of self builders do not come from a construction background and few of them know much about the ins and outs of project management.

The prospect of spending a six-figure sum on something as intangible as a ‘new house’ can cause anxiety. Because of this, self build in the UK today is still seen as being a little heroic, because many people would baulk at undertaking a large building project with their own money, when the outcome cannot be known in advance.

It doesn’t have to be reckless, however. One of the keys to reducing the amount of risk involved in self build is to take control of the budget at an early stage. To do that, you need to develop an understanding of how building projects work and where exactly all that money goes.

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Costs for Self Builders

pie chart showing the division of costs for a self build project

The pie chart above provides a breakdown of the costs involved in a typical self build project. It shows that the superstructure (i.e. the structural walling and external cladding, as well as roofing) accounts for the largest proportion of the costs, typically 25-30%, with the foundations and floor structure following closely behind.

Most importantly of all, it reveals that the remaining elements of a build each tend to account for between 5-10% of the total cost. The key is to recognise that individual elements can be reduced later on if other elements go over the initial budget.

The outline of the packages in this pie chart also serves as a useful starting point for self builders looking to assign budgets against particular elements.

Costs for Renovators

pie chart showing how much different parts of a renovation cost

This pie chart analysis of the costs incurred in a remodelling/extension project shows a disproportionately high windows package element, accounting for some 15-20% of the overall build budget. This is because the design in question specifies high-quality triple-glazed windows with aluminium frames — and lots of them. The good news is that because a higher than average portion of the walling is covered in glass, the subsequent costs of blockwork, timber, brick and stonework are less than might otherwise be the case.

Costs are more difficult to predict when it comes to existing homes as builders struggle to quantify labour hours/days associated with remedial and demolition work. This renovation budget allows £10,000-£15,000 for such works (including the addition of steel joists, etc.).

This budget plan contains more detail than the self-build chart. The more detail homeowners can put into spreadsheets like this, the better for planning purposes and the more rigorous the approach to budgeting for labour and materials quantities.

Comparing Walling Costs

Note: Costs are approximate but designed to provide a starting point for a budget. Bricks, for example, vary between 30p-£1.20 per brick. Stone can cost £25/m2 up to £180/m2, plus laying.

  • Windows: £370/m2 £300/m2 materials + £70/m2 labour
  • Blockwork: £25/m2 £10/m2 (£1/block) materials + £15/m2 labour
  • Bricks: £60/m2 £30/m2 materials (50p a brick at 60/m2) + £30/m2 labour (500 bricks laid per day (8.3m2) @£250/day)
  • Stone: £150/m2 £75/m2 materials + £75/m2 (labour based on 3m2 laid per day)
  • Timber: £50/m2 £30/m2 materials + £20/m2 labour 

What’s Included in the Floor Area?

One trap for the unwary is the way that building areas are defined and referred to. It’s all very well deciding on a budget per m2, but what exactly do you get for your m2? What’s included and what’s excluded?

The m2 used in the calculations is the internal floor area, or heated area, of the house. It specifically excludes the ground taken up by the external walls and any ancillary buildings such as garages and outhouses. It also excludes unused areas in lofts and under the eaves, unless they are specifically opened up as living space. A four bedroom house with an internal floor area of 150m2 might easily have a gross floor area, including the garage, of 200m2.

Does this matter or is it just academic? It can do, especially if someone tells you they can build you a house for, say, £1,000/m2 only for you to find out later that their m2 is somewhat smaller than the industry standard way of measuring. It is also worth bearing in mind that other countries (Sweden, Germany) use different measuring criteria and that their build costs/m2 cannot be easily compared.

Labour vs. Materials

Installation can be the hidden cost when it comes to preliminary budgeting — ignore it at your peril. But the amount of labour required on each package varies hugely. The examples below show the differences there can be between labour and material cost for different elements of a build.

Windows

windows labour versus material costs

Labour (in blue) tends to account for around a fifth of the total price, depending on the window specification

Stonework

stone work labour versus material costs

Stone can be expensive to purchase, but takes a long time to lay, with most stonemasons managing 2-4/m² a day — hence the high labour costs

Establishing the Initial Budget

The majority of self builders start off their journey with a figure in mind of what they can afford to spend. Many of them will refer to our build cost calculator, where a sample of different projects are compared in price, presented as price/m2. The current costs range from around £800/m2 through to just over £2,000/m2. The table identifies five variables impacting on the final sums:

  • Build route (how you manage the project) — 40% variation.
  • One or two storey (two storey buildings are cheaper on a m2 basis, but only marginally)
  • House size (it gets slightly cheaper per unit area as the size increases)
  • Standard of finish (the table allows for a 40% difference between ‘standard’ and ‘excellent’)
  • Location (the UK is divided into four zones — the most expensive being 30% more than the cheapest)

There is not much you can do about location – short of deciding to build somewhere else – but the other variables are very much in your control. What you choose to build, how you choose to build it and what finish standard you are looking for are all factors determined by you at the outset. The cost calculator enables you to work out where in the self build spectrum you stand and to give you some indication of what you might get for your money.

Not everyone wants to shave costs. If it’s your first house, you might well be trying to build as much space as you can afford and to fit it out as cheaply as possible, using all that youthful energy to undertake DIY and/or project management. In contrast, a retired couple might choose to build a smaller home but fit it out to a higher standard, and to let the professionals carry out all or most of the work.

Bear in mind that over the years Homebuilding & Renovating has covered self build projects with costs ranging from £300-£3,000/m2. The build cost calculator, however, deals with the most common projects.

A Note on Project Management

In theory, you have control. In practice, it may not be quite so simple. For instance, if you are living well away from the site, it will be impractical to take on the management of the project. To do this, you need a site presence. Not necessarily all day every day, but at least at some point every day. You are going to have to be taking delivery of materials, arranging storage and making sure that everyone working on site is fully occupied.

This sort of thing doesn’t happen by magic: while many people are quite capable of taking on this role successfully, they have to be fully engaged in it otherwise it will tend to be done rather badly, which in turn adds to delays and costs. So while the calculator indicates that a DIY management build route may save 40% over a professionally managed fixed-price job, it is not an option for everyone.

How to choose a build route

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