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Factoring in ALL costs of a self-build

Updated: Aug 11, 2020

How much does it cost to build your own house?

If you’re deciding to embark on a self-build project, you will no doubt realise there are many elements that will need factoring in from a cost point of view. You may have a rough idea of your total budget when it comes to self-building, but how much does it actually cost to build a house?

Understanding how much it costs to build a house is a vital starting point for any home building project, including the hidden extras, which often go overlooked.

Size Matters

The bigger the house, the more it will cost to build, but there can be some economies of scale that reduce the average cost/m² for larger houses, making a carefully-designed large house better value.

The savings are mainly in the cost of building the superstructure, especially the foundations, walls and roof. The cost/m² of gross floor area for external walling elements decreases as the wall/floor ratio decreases.

Other one-off unit costs for items such as service connections, staircase, kitchen and boiler are spread out further on a larger house. To maximise efficiency, the design needs to be kept simple and avoid unusually large spans for floor joists/beams, rafters etc.

Cost breakdowns are normally split into the following categories:-

  • Construction system

  • Services

  • Foundations

  • Cladding, Render and Exterior Finishes

  • Roof

  • Floor structure

  • Walls & Ceilings

  • Staircases

  • Chimney

  • Windows

  • Kitchen

  • Bathroom

According to this pie chart* from Homebuilding & Renovating, it shows that 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.

*Credit: Homebuilding & Renovating

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.

Make sure you have a contingency budget

The balance of funds is your build budget. It’s a good idea to set aside 10–15% of this as a contingency for unforeseen costs and to pay for architectural design fees (typically around 5–6% of the build cost).

Check out the Homebuilding & Renovating Build Cost Calculator to cost your self-build project.

Hidden costs – don’t overlook…

  • Legal Fees: £500-1,000

  • Stamp Duty and Land Tax: The tax is currently levied at 2% for land or house purchases valued from £125,001 to £250,000, 5% for plots valued from £250,001 to £925,000, 10% between 925,001 and £1,500,000 and 12% above £1,500,000. (Bear in mind that self builders buying a plot which is effectively a second property are liable to pay the additional 3% surcharge but are exempted from it if they sell their old home within 18 months of buying the plot).

  • Topographical Site Survey: Typical cost £350-500

  • Design Fees: Architects charge 7-15% of the total build cost for a ser­vice involv­ing design and supervision. For planning drawings from other sources expect to pay from £2,500-£3,500, plus a similar figure for Building Regulations drawings

  • Structural Engineers’ Fees: £400-£500

  • Planning Application Fees: £462

  • Building Regulations Fees: £500-£1,000

  • Warranty: Around 1% of contract value

  • Self Build Insurance: Typically 1% of the projected build costs

  • Services: Typically £3,500-£6,000 total

  • Demolition Costs: Typically £5,000-£10,000

  • External Works: Around 15% of total build cost

  • Preliminaries: such as setting up a site office, scaffolding, fencing, security and safety equipment and skips. Typically costs £5,000-12,000 for a new house.

The importance of project insurance.

Self-building or renovating can be risky business so it’s important to insure your self-build project and make sure that you don’t under-insure. A major scheme involves valuable, heavy machinery and expensive materials waiting to be used.

Risk can exist in familiar issues like liability, theft, storm damage and fire, but also unfamiliar issues like tradesmen not completing the works satisfactorily, your contractor utilising unsuitable materials to complete your project, or your builder accidentally damaging your home. We have a vast amount of experience in providing the custom build home insurance you require and a deep understanding of the types of projects you are likely to undertake, so you can count on us to take care of your needs.

Site Insurance is necessary to protect your investment when you’re carrying out a renovation, conversion, extension or new build. The policies cover the new works, existing structure and rest of the site. It protects against the likes of losses, fire, theft, flood, storm damage, vandalism and accidental damage. You can view the specific project pages for in-depth information on Self-Build Zone's structural insurance:



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