When you are searching for a property to buy or rent, one of the first things you’ll look for is the size shown on the floor plan. Usually presented in square feet and square metres this statement should give you an honest appraisal of the ‘habitable’ area for a property.  However, it’s not always entirely straightforward.  An understanding of what the GIA means and how a floor planner will arrive at the final figure can be helpful in weighing up the pros and cons of properties and their comparative value.

What does Gross Internal Area (GIA) actually mean?

In broad terms, GIA is the entire area within the shell of the external walls.  This includes the space taken up by internal walls, chimney breasts and wooden seating areas created within bay window areas.

What rules govern how GIA is calculated?

Mays Floorplans follow the Royal Institute of Chartered Surveyors (RICS) Code Of Measuring Practice (6th Edition).  This gives us a guide for what can be included and should be excluded.

As with any rules, these can occasionally be open to interpretation.  However the most important point is not to mislead or be ambiguous. Where there is a ‘grey area’, such as a garage that is connected to the property with a door, we will clearly state whether it is included or excluded from the GIA shown on the floorplan. It’s worth looking out for this information so that you are clear on the size.

Why do floor plans normally state “approximate” GIA

Two floor planning companies can measure the same property and genuinely get a slightly different result, potentially up to as much as 1-2 square metres on a 3 bedroom flat. This can be due to rounding figures up or down, or depending where a laser measuring device has been placed on a wall.

For example, many Victorian properties do not have straight walls internally – it’s part of their character! However due to their slightly wavy nature, two people could measure the same wall in different places and get a one or two inch difference in room width. If this small difference is multipled across the length of a property two floor planners will calculate different GIA figures.

It’s our duty to measure and calculate Gross Internal Area as accurately as possible. An urban myth in wide circulation is that “approximate” means that the accuracy has a tolerance of 9-10%. However, RICS states that for residential properties the tolerance from the true GIA figure should be +/- 1%.

It doesn’t pay to exaggerate GIA. The legal issues.

Sometimes we are asked increase our GIA to match a previously drawn floor plan.  In rare cases this can include the accusation that we have produced a plan “smaller” than the reality. Unfortunately, in these instances nine and a half times out of ten we find that there are inaccuracies or exaggerations with the previous floor plan leading to a mis-representation of size.

This places us and our estate agent clients in a difficult situation. Imagine you have bought a property advertised at 900 sq ft in central London, where the valuation can be based partly on the property size down to the very last sq ft.  On selling you find the new floor plan shows a different size, potentially placing the value of your property at less than you feel it should be.

In extreme cases this can lead to legal battle with the estate agent from whom you bought the property.  Where the mis-representation has been knowingly carried out by an unscrupulous agent, vendors have successfully sued for compensation.

Good agents will always consult us if there are significant differences in floor plan sizes.  Mays Floorplans are happy to be considered trustworthy and transparent in our calculations and communication.

A good floor planning company will always be happy to explain their calculations.  We know how important accuracy is.  Misleading exaggerations are thankfully rare and often slight differences in measurements can easily be resolved.

Of course if a property appeals to you or is in the right location and has everything you want or need, the GIA – even a 100% accurate one – is simply one factor in the equation.

Mark Hewitt, Business Development Manager at Mays FloorplansMark Hewitt, Business Development Manager, Mays Floorplans Ltd