One of my favourite statistics (and yes I do have a few) is that the average Victorian semi is made up of about 40,000 individual elements, bricks, timbers, tiles, pipes, wiring and everything else.  Of these only about 10,000 are visible, so how can a Surveyor be certain about the extent of any problem when he can only see a quarter of the building during a survey?

Training and experience play a big part in this as well as some great modern equipment such as damp meters, thermal imaging and endoscopes.  But there is one area where statistics also play a part and that is structural movement.

The starting point is BRE Digest 251: Assessment of damage in low-rise buildings.

Following a study of 130 properties suffering from subsidence, five kinds of crack were identified, categorised primarily by width. In simple terms, the study found that, categories 1 and 2, cracks of less than 5mm, were essentially aesthetic problems only and unlikely to indicate a significant structural issue. Cracks in categories 3 and 4, of between 5mm and 25mm, were found to cause serviceability issues, such as sticking doors or penetrating damp. Anything in category 5, being more than 25mm, was considered to require structural intervention.

Based on the above I know that if I see a 4mm crack, statistically speaking it will be safe but of course statistics only take you so far.  What if the crack has developed over a short space of time and is getting bigger? What if there are a lot of 4mm cracks?  What are the chances that there are other cracks hidden in the ¾ of the building I can’t see?

It is at this point that the Surveyors good skill, experience and judgement comes in.  If you know how the property is constructed and what the sub-soil beneath the property is like plus considering a few other factors you can work out what is likely to be causing the cracks.  A good Surveyor will then be able to make a judgement about the extent of any problem as well as advise on the next steps.

To book a Building Survey or Home Buyers Survey carried out using statistics and good old fashioned experience please contact us.