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Cost of Project 

There are a number of variable factors that will affect the project cost. As a very rough guide, cost can be estimated as follows.

Location/ Contractor

Depending on your location and the demand for contractors, the price will be higher if there is a lot of building work going on around you. London is around 10% more expensive than the average cost due to contractor and material costs.

Internal Finishes & Fit out

Internal finishes, can vary greatly, so be aware of the rough cost from the supplier if you have something particular in mind. Kitchens and bathroom also vary hugely in cost, you should factor in the cost for these items separately to the construction

Amount of glazing

If your vision is for a super modern highly glazed extension, you should be aware that this will increase the construction cost significantly compare to standard extensions that integrate with existing building design.

Type of roof on extension

Flat roofs on an extension will generally save you on cost if you are not including large skylights on the flat roof. A large roof light will normally require steelwork as structural support and therefore bring the cost to higher than a pitched roof.