We are planning on building a house of 39 feet long by 24 feet wide but done know how to work out the floor area to calculate cost it will be 1.5 story and have 3 bedrooms upstairs with one en suite and family bathroom how is the floor area calculated in order to work out cost? Thanks

  • Rebecca Clutton

    Hi Carol-Ann

    A simple calculation would be 24 x 39 x 1.5 = 1404 square feet. This is equal to approx 130 square metres and you can calculate your approximate building costs from the tables HB&R have prepared.. Very rough rule of thumb is £1000 per square metre but there are many variables to take into account such as how you will build your house, where you are, what finish you are aiming for etc.

    I would strongly urge you to seek advice from an architect or at the very least technical drawer for further help on working out area spaces etc. good luck with your project.

  • Lindsey Davis

    Hi Carol-Ann,

    Now you have the measurements, you can use our Build Cost Calculator to calculate the cost.



  • Mark Brinkley

    I’m not sure I go along with Rebecca’s calculation. It’s not a 1.5 storey house, it’s a 2 storey house. 1.5 storey is shorthand for building the upper storey into the roofspace which is arguably more expensive than just placing a simple roof on top of a 2 storey house.

    There is another problem in your calculations which is that I guess your measurements are external ones, whereas floor area calculations are normally based on internal floor measurements. External floor areas are normally about 10 – 15% larger than internal ones – the difference being made up by the area of the external walls.

    My estimate from the information you have supplied would be that your internal floor areas will be c 160m2.

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