Self-build homes: How to estimate your costs

When planning your self-build project, one of the most significant elements is assessing the costs.

Often, in a build project, the costs can vary significantly, particularly if part of the project does not work out as planned and contingency plans need to be put into place.

How much will it cost to build?

Establishing how much you have available to spend is the first step. Combining your equity from the sale of your current home, savings and other funds, which might include a self-build mortgage.

Buying land

It may be that you already own a building plot or have a large garden space suitable to build on. If you don’t, you need to take a look at the price of land in your areas and allow for the buying costs associated with the land including legal costs and stamp duty.

If land is in short supply in your preferred area it may be worth considering buying a derelict or old property, demolishing and then building new.

Service connections

Take into consideration the costs to connect water, drainage, electricity, gas and telephone, costs to implement these can range from £7,500 to £10,000.

Contingency funds

It’s worthwhile setting aside 10% – 15% of the balance of your funds as a contingency. This should cover any unforeseen costs and can be used for other desirable items if no unforeseen costs arise.

Consultants Fees

You should also be prepared to set aside around 10% – 15% of the likely build cost for fees, including Planning Application and Building Regulations application fees and of course your architect, structural engineer and other consultants that are required.

How to calculate your build costs

A good place to work out your fees is the build cost table and establish the average build cost per m2

Factors that affect build costs


The bigger the house, the more it will cost to build. To maximize efficiency, it will need to be well designed by your architect to maximize space and avoid large areas of circulation or wasted voids. Using roof spaces to the maximum is a good example of this.

Plan, shape and layout

The simplest and most cost-effective floorplan is square. A rectangular plan requires more wall for the same area, therefore increasing costs. Other factors such as curves, more angles, and angles other than 90 degrees can all create additional costs, but will often create a more interesting design that may be more important to you than the cost.

Additional factors

Number of storeys


Project management

Will you manage the project or pay someone to handle it for you?


Can you make any cost savings by doing some of your own labour, even the final decorating or garden areas?


Dependent on your budget you may be looking for a high specification or a low specification build. The following factors also need to be considered as part of this:

Construction methods

Level of insulation in external fabric

Heating/Ventilation Systems & use of Renewable Technologies

Claddings, renders and exterior materials

Extent of Smart Home Technologies/Controls

Glazing extent and specification

Roof design & specification

Foundations type/options

Floor structure options

Walls and ceilings spec

Staircase design

Chimney type if required

Windows and doors



Garage/car-port/ancillary spaces

Fixtures, finishes and utilities

Internal and external lighting

External works & landscaping

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