Measured Building Surveys

- Buildings Are Not Square

Traditionally, Building Surveyors when carrying out refurbishments, have used the tape measure and digital laser measuring device, such as the Disto, to name the common trade name, since the system normally involves lots of paper (graph paper if you are organised). It is usually the assumption that the buildings are square, which as we all know, as they are hand built by human beings, is not often the case!

Generally, it is okay up to about 500 metres squared, anything above that and it is generally recognised that you do a boarder first approach, just like on a jigsaw, where you do the outer edges first. However, unless you triangulate you will again have to assume that buildings are square and fit the rooms within the outline of the building. Any chance of building a square 20 metres x 10 metres and then skewing it? With towns and cities retail office space and warehouse space is measured in per square foot (or is it square metre?); this can make a massive difference.

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The accuracy of available information

Ordnance Survey and maps taken from this information are generally considered to be accurate, particularly where they are 1:250 scale. However, actual measuring of the land areas of 1:1 scale shows them often to be slightly inaccurate. The test that we were shown the inaccuracies range from 300mm to half a metre over approximately 20 metres in length. The rents / rates are calculated on net internal areas (NIA) correct measuring and checking that the building is square or otherwise (it is normally otherwise) and is very important. In fact we know of one building surveying practice that spends all their time re-measuring old office blocks and surprise, surprise they are not as the drawings and they are not square, and this is brand new buildings.

Specialist Measurement Companies

Specialist companies are available to do this type of work, but often building surveyors do it themselves. They generally carry out measured surveys in the following format:

Unconnected - this is where the measure the net internal area only.

Reconnected where they measure the internal and externals and join them together and check the squareness, etc, but make assumptions on the vertical.

Fully controlled where 100% accuracy is used in sophisticated measuring devices.

Level of accuracy needed on a measured building survey and appropriate accuracy

As measuring a building 100% accurate can be very time consuming and therefore costly, you need to decide on the appropriateness of the measurements by carrying out a structural survey, basing your external tape measurements may be sufficient. Where if the building survey has also asked you to comment on structural problems you may wish to be more accurate than this, alternatively, if they have asked you to comment on extension opportunities greater accuracy will be needed.

Thanks for David Maltby, Andrew Maltby, Richard Maltby,

Stephen Maltby and Jason Bird of MBS Survey Software Limited.

Please see the oxymoron article written by Andy Roberts of MBS Survey Software Limited, surveymbs.com