As a chartered building surveyor operating in France and the UK I regularly get asked, amongst my normal survey and project-management work, to do 'partial' house surveys. This often means doing a survey of some cracks the punters have seen on their visit to a property. Nothing seems to bother people like cracks. They look scary and if beyond the scope of "Polyfilla" I swing into action.

As a building surveyor I try to resist one-item surveys. There are many other defects just as scary and likely to ruin an investment, let alone the enjoyment of a property. If I am doing a survey the client has me there with all of my equipment so why not have the whole place checked out? It does not cost that much more and I can then do a thorough job and give them the whole picture instead of a just a snapshot. On the other hand, you get what you pay for and if you are only bothered by the 'cracks' then who am I to argue.

I can understand the single-minded approach in some cases. I recently inspected a potential three-storey apartment building in Hesdin that had some impressive cracks in the flank walls and also to a rear addition. Just to get boring for a minute: cracks are classified in 5 categories, from hairline to very severe. We have all seen hairline cracks in walls and ceilings and we live with them. They are part of the UK house construction system we like, i.e. bricks-and-mortar. In North America with their lightweight timber-framed and dry-lined houses cracks, even hairline cracks, are rare but not in our rigidly plastered boxes. Ancient buildings in the UK and in France constructed of rough-hewn timbers with wattle-and-daub infilling rarely have any cracks. These materials are natural, do not harden like concrete and so can accommodate general movement without cracking. The structures are also relatively light so do not need massive foundations.

In the Hesdin property the cracks were in the 5th dimension, very severe, see photos. The back addition was subsiding and the staircases were straight out of the Wibbly-Wobbly House. None of the internal doors would close as the openings were seriously distorted. This was a property that was being supported by its neighbouring structures and was just too heavy for its own superstructure. I am not usually concerned about walking through an old building but this place had me nervously testing every step before I put all of my weight down. I was glad to finish the survey and get out.

Checking for cracks and more importantly, deciding if they are significant, is a science and takes years of experience. I have 40 years experience as a building surveyor, from my trainee days up to now as a principal in my own firm. When I started doing surveys I assumed that every crack was a serious defect and signalled the imminent demise of the property.

Now I know that cracks can be sneaky and look worse than they really are. Some open up in the summer and close in the winter. Others are early indicators of real subsidence and should not be taken lightly. Others are due to either thermal movement, drying-out or simple settlement that occurs in every building. Some are down to poor workmanship or unsuitable materials. A building surveyor has to be able to distinguish between the really bad and the plain ugly. In some cases we have to advise on a long period of monitoring, using crack gauges, to find out if the movement is active or historical. This does not suit a homebuyer, even in the relatively slow French system, but that is not the surveyor's concern. We have to work with the natural cycles of the seasons and not with legal timescales.

I usually find that older rural French properties, particularly converted farm buildings, fermettes and the like can have significant cracks, see photos. The standard of construction in these building is often poor using cheap materials and probably done by farm-labourers moonlighting as 'builders'. Some of the brickwork is so poor I must have done it myself in another life. I tried once to brick up a doorway with nice plumb jambs to work to and still managed to make a dog's breakfast of it.

In plain language, if a crack has the impetus to shear its way through solid brickwork it is not good news. If I can see daylight though a 300 mm thick wall this is not good news either. Depending on the size, direction and the tapering, if any, I make a judgement on the seriousness of the crack. I then look for other factors related to the cracking such as bulging, bowing, leaning, internal doors that do not close, etc. to form the whole picture of what is happening to the structure. In some cases I have to advise on further investigation. This is not a cop-out. If I suspect that the foundations are too shallow, being undermined or just plain non-existent I may have to recommend trial pits around the building to see what is actually holding it up. When the boffins bring out a gadget that can see below the ground I will buy one. Until then clients will have to accept my limitations. (I have even been asked to inspect septic tanks but that is a whole new article! Irene, where did you put my snorkel and green wellies?).

A lot of older French rural properties were built off of rammed earth with no concrete-filled trenches as expected today. This can be fine until the old lightweight, 'torchis' walls are replaced with much heavier brickwork and/or the new guttering leaks in one spot and softens the ground to an extent that the house is sitting on 'porridge' (or should I say muesli) at one corner. The French seem to think once the rainwater is off the roof they can forget about it and just spew it around the base of the walls. Even in North America they insist on long ground-spouts to discharge the water well away from the house walls and footings but these are rare in France. In the UK we use underground pipelines to drains or soakaways.

The causes of cracks are as varied as the cracks themselves. There have been countless books written on the subject (yes really) and trees are usually blamed for subsidence and the cracks that go with it. You would think that in the past two thousand years we could have worked out how to build near trees. I blame the buildings and not the trees. If we are going to build miles away from trees we might as well cover the whole Earth in concrete.

To put the subject of cracks in perspective: I have never witnessed a building collapse or get to a state where it was unsafe to live in. It does happen but I have not seen it myself. The building at Hesdin is the nearest I have seen to vertical rubble but it will probably last for decades. Cracks are unsightly and we have a natural urge to cover them up and get rid of them. If you have a full survey done you will be forewarned of any cracks and given advice on what needs to be done, if anything.

As a final comment on cracks to concrete paths, driveways, steps and the like. A learned old surveyor let me in on one of his standard responses to clients' questions on the subject.
"There are two types of concrete" He would tell them. "Concrete that has cracked and concrete that is going to crack". I repeat this pearl of wisdom all of the time. Copyright 2008 Martin Quirke FRICS

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