Sign in / Register

How to Estimate Your Own Build Costs

It’s the number one nightmare for self-builders and renovators: a project spiraling wildly out of control, with the budget blown and financial disaster ahead. The good news is that, despite what you might think after watching an episode of Grand Designs, this situation is easily avoidable.

Everyone starts out on a new build or renovation project with a set figure in their head of what they would like to spend. There’s probably also a figure in the back of their mind that is the absolute limit they can go up to. These figures – the budget – are critical to the success of the project regardless of its scale or ambition.

The trouble is that for most people new to the process, getting a realistic idea of what these costs might be is very difficult — for various reasons. Most commonly, when a new self-builder asks what it might cost to build their own home, the answer is simply impossible to give, because there are so many unknowns.

If getting an accurate idea of what your project will cost – and, just as importantly, ensuring that it stays within your budget expectations during construction – is important to you, then you’ll need to do some in-depth DIY estimating, or get some professional help.

DIY Estimating

First things first, in order to estimate your build costs accurately, you will need a correct (and final) set of building drawings. It’s impossible to be specific about expected costs if you don’t yet have access to the full detail of materials required (from type of joists and bricks through to finishes). If you are still keen to come up with an estimate of your expected costs for a self-build project, then use the build cost information on this very site (Build Cost Calculator). It gives, based on a series of questions regarding expected quality of finish and personal involvement, an estimated cost/m². Based on figures published by the Build Cost Information Service – part of the Royal Institute of Chartered Surveyors (RICS — the body that regulates chartered surveyors) – it offers about as accurate a ‘guesstimate’ as you can hope for.

Extensions and renovations are much harder to give estimates for as the limited floor areas/individual nature of projects renders cost/m² figures meaningless.

If you have detailed building drawings then you could use an estimating company, such as My Building Project Estimating Service. My Building Project has been developed by HomeBuilding & Renovating Magazine in partnership with HBXL – the market leaders in estimating solutions. For a set fee (up to 300 sq m - £399 plus VAT, 301 – 400 sq m - £499 plus VAT), our estimating service will provide you with a comprehensive and independent estimate of how much your new home will cost to build - a detailed breakdown using real labour rates and highly competitive live prices for materials from leading merchants.

Builders’ merchants will, on the whole, be happy to offer a free ‘take-off’ service from your plans (quantities and costs for materials but not labour), however this is only the case if they can be assured of getting some level of work out of the deal.

Secrets of Budget Control

• Get the design settled and in line with your budget. Employ a designer who understands your budget and has proven examples of finished projects brought in on similar costs.

• Don’t go out to tender with builders until you have nailed your specification. Send out copies of full building drawings and detailed specs of material requirements. 

• Don’t change your mind along the way, and if you do, ensure you have a process in place for agreeing the extra costs incurred.

• Employ a quantity surveyor on larger projects to give you an expert assessment of the cost of building to your plans; and retain their services during the project to ensure costs remain under control.

Calculate how much your new project will cost to build with our free Build Cost Calculator

4 Comments

Dear Sir I fully understand the peramiters laid out in the preamble to the cost chart and its various allowances dependant upon region and quality of build. What I cant understand is to what extent are site specifics included such as drainage, buliding statutory services such as gas, water, electric, telephone etc. and the varying degree of external works and site preparation. I have no intention to confuse the issue but may I take it the rates are exclusively for the build and any site specifics shouild accounted for seperatly? Your comments would be appreciated. Ian Grove (2126716)
Hi Ian, You are correct in your assumption that any building statutory services are not included in the costs due to the many variables that can arise in this area. Basic site preparation however, including standard drainage, is included in the costs albeit this refers to the costs of laying pipes etc as opposed to the costs of connecting to any mains sewer. Hope this clears things up. This article breaking down drainage costs may be of some use to you http://www.homebuilding.co.uk/feature/costs-drainage Kind regards, Sam Joy (Online Editor)

I have a question regarding the allowances in the Build Cost Calculator for Bespoke Joinery / Kitchen. The notes state that £40/m2 is allowed - but this appears to be for all three build quality levels. Surely a greater amount is allowed in the 'Excellent' category than in the 'Standard'? For example, the Excellent model assumes a bespoke kitchen rather than the contract kitchen of the Standard model. Could you explain my confusion? With thanks.

Hiya,

The £40/m2 is the cost assumed for a standard kitchen. Since prices vary so much in regards to bespoke kitchens, the idea is that one would get a quote (minus VAT) for their desired kitchen then add that to the current build cost total. From this figure, minus the size of the planned kitchen multiplied by the £40/m2 that was allotted for a standard kitchen.

Hope this clears things up.

Kind regards,
Sam