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When I carry out pre-purchase house surveys in France there are major and minor elements of the building to report on. The roof is without doubt in the major league. A roof is a defining element of a home. We say we want "a roof over our heads". Walls without a roof are not a home whereas you can have a home without walls. In some parts of the world, homes are virtually just a roof on stilts. Tepees are basically a pointed roof and so are Swiss Chalets if you stretch your imagination a little. My point is you have got to have a roof. Even cave-dwellers had a roof.

The roof takes the brunt of the weather and when properly designed, with generous overhangs, it protects the outer walls and windows from rain, snow and hail. If you go to wet parts of the world you will see big roof overhangs with steep slopes to throw off the moisture quickly and efficiently. Even flat roofs can be effective if they are at least 10 degrees to the horizontal and have generous oversails all round. As a chartered building surveyor I prefer traditional pitched roofs. They are low-maintenance as well as being far more attractive. I do not survey many flat-roofed homes in France so I will concentrate here on the pitched variety.

If you are buying a new home pay particular attention to the roof. You ignore it at your peril. If a roof leaks the water damage can be horrendous to furniture, fittings and décor. A new roof is very expensive and re-roofing work is disruptive.

If the property you are looking at has a slate roof be aware of the very high cost of replacing it. Slate is the most costly roof-covering, with clay tiles next and concrete tiles and shingles being the cheapest. If the property is of architectural merit you may have to replace like-for-like so do not assume you can throw up some lifeless, man-made slates while no-one is looking. Slates last the longest, 80 to 100 years, so they are good value for money in the long term. Like everything else, slates come in various qualities. Imported Chinese slates are the cheapest that I know of. Spanish slates are dearer but slightly more attractive. Angers, Bretagne and the Ardennes are well-known sources of French slates. Not all slates are plain grey. The natural colour varies between the regions and my personal favourite is the blue-black variety from the Causses, the Pyrenees and the Alps. There is even a slate the French called 'anglais'. Hope it was meant as a compliment! There are fibre-cement slates too but these fit into the same category as plastic windows and MDF joinery. Fine if you want to save money but having less character than a blob of margarine. My worst nightmare is a fibre-cement roof over walls covered in plastic shiplap boarding with plastic windows and doors and a house full of MDF joinery.

In my experience slates are only found on the grander French properties. So if you are looking for a village house the likelihood is that the roof will be covered in natural clay tiles. Clay is a fabulous material. Good quality clay tiles last almost as long as slate, 60 to 80+ years. They retain a lot of their original colour over the years and weather (age) nicely. Clay is far cheaper than slate too. If the roof tiles are a warm, terra cotta colour they are almost certainly clay. Clay tiles are relatively light, usually uneven and slightly irregular with a smooth fine texture. Unlike slates tiles come in a wide variety of shapes and sizes as they are made in moulds and not cut from rock. The concrete tile manufacturers keep trying but they are still way off reproducing the warmth and depth of natural clay. Concrete is made from cement and this material, although practical and useful in structural situations, is lifeless.

Concrete roof tiles are cheap, regular to the point of being featureless and long-lasting. If you like concrete they are for you. You can even get a concrete 'slate' that looks just like real slate from 500 metres away if you look through squinted eyes at night. A word of warning: do not use these concrete heavyweights to replace real slates, unless you structurally upgrade the roof-frame. Real slates are thin and very light and do not need a beefy roof-frame to support them. Concrete is heavy and needs a whole different grade of timber support. When I see an old house with a new, sagging roof I pretty much know what has happened. A 'roofer' has taken away the light stuff and replaced it with concrete tiles weighing over three times as much. The timber frame sags under this increased weight that it was never designed to carry.

I do two types of pre-purchase house survey. One is called 'roof-and-walls-only', so you get the gist of what this is all about. It gets right down to basics and ignores anything not on the tin. The other type of survey is the 'building survey'. Predictable title but not as exotic as the now defunct term 'structural' survey. I wish the RICS had kept the old description but they wanted to be more user-friendly and wide-ranging. Both surveys include an equally close look at the roof, subject to access and visibility.

When surveying a roof I do not climb on it, scale it or hang-glide over it, as some clients expect. Furthermore I do not carry a 6-metre ladder on my roof-rack or a collapsible scaffold tower in a trailer. If I was in a Monty Python sketch I might try a big pogo-stick or a trampoline. Instead I use high-powered binoculars and years of experience. I walk around the property and view it from all sides. This in truth means I cannot see the hidden valleys and slopes, backs of chimneys, etc. but I can usually see over 80% of the roof. I inspect the attic so I get a good idea of the overall condition, inside and out. With my binoculars I can almost see the roofer's fingerprints on the tiles so I do not need to get any closer. Happily for me I am not risking my life and limb and I can study the roof at my leisure. I get the occasional odd look from neighbours but I make a point of being out in the open and not hiding amongst the trees or bushes for obvious reasons. I would not want to explain to the flic in my poor French what I was doing in the bushes with high-powered binoculars! Looking at the roof tiles, yea right - come this way monsieur.

Roofs do not usually age evenly. The slopes facing the prevailing weather are more likely to wear out first. The front of your car is more weather-beaten than the back and this is the same principle. People are more likely to repair and re-roof the slopes that are visible from the street than the slopes no-one sees. I can often be walking up to a house for the first time and have the impression of a 'new' roof, until I view the whole perimeter. You cannot blame home-owners for replacing only the worst-affected parts of the roof, as sheltered slopes can last twice as long.

Perforations are the weak parts of a roof. Every perforation is a leak waiting to happen. You can use the analogy of the cracks in concrete: there are two types of perforation, one that is leaking now and one that will leak in the future. Surveyors will tell you that there are two types of concrete; concrete that has cracked and concrete that is going to crack. In the UK we tend to use good-quality lead for flashing around perforations but the French prefer zinc. It is cheaper. Zinc is perfectly fine but shorter-lived and less flexible than lead. The worst flashing is the sand/cement fillet applied along the angle joining the tiling to the chimney (or whatever). Cement is a hard, inflexible material that cracks easily. Rainwater gets into cracks. Even when a lime (soft) mortar is used the fillet is unsuitable in the long-term. I could not count the number of times I have gone into an attic and seen severe water stains on the chimneystack or party/gable wall where rain is getting in behind the flashings. It is as predictable as finding damp in solid-walled houses.

Sagging is a common fault. It can mean that the rafters or ridgeboards are rotting or deflecting. As mentioned above it could also be due to the wrong type of roof-covering. However 'sagging' can be confused with the presence of rough-hewn timber frames. I have inspected many French attics where there is not one straight piece of timber visible. In modern homes we expect everything to be level, plumb and straight but this was not a high priority in days gone by, especially in rural areas where farmers also did the building work. Power-tools were unheard of and axes were the main woodworking tool. If you try and cut a straight piece of timber with an axe and you will see how impossible it is. These old roof frames were fashioned out of large branches so the 'sag' or waving might be nothing to worry about. If you look at my photos you will see what I mean.

I have not mentioned roof-coverings such as zinc, lead, thatch and shingles as these are rarer than tiles. Thatch is worthy of an article on its own and I had quite enough of shingles during 5 years in Canada. Out there the attitude is why go for a heavy, expensive, long-lasting material when the house will be pulled down and rebuilt in 20 years time. Tiles are a rare sight in North America although more common where the winters are harsh. On the other hand in France most houses are expected to last 200 years at least so why use something that you will have to replace often. Typical French logic.

Finally, the subject of ventilation and insulation to roof voids. Without getting too technical, there are 'warm' roofs and 'cold' roofs. The cold roof is the one we all know where the insulation is laid across the ceiling. The space above, i.e. the attic, is cold and uninsulated. Here the need for ventilation is essential according to most experts – some dispute it. Ventilation removes the moisture rising up from the living areas which settles on the roof timbers as condensation. If the timbers get above 19% moisture content they can rot and hence the need for ventilation to move the moist air outside. Surveyors' moisture meters are designed to show moisture levels in timber for this reason. I have been inside 200 year old attics with no visible ventilation and the timbers are free of any rot but maybe trees were tougher in the old days. Building regulations call for ventilation in the attics of new homes so on balance it is seen as worthwhile. Warm roofs are those where the thermal insulation is located between the rafters and therefore the attic space is fully insulated and 'warm'. Because the undersides of the rafters are not cold, condensation cannot form and so no ventilation is required. This is the theory anyway. So if you see ventilating roof tiles on the slopes or venting ridge tiles they are there to prevent decay in the structural timbers. Some roofers seem to be unaware of this and blindly install the underlining across the whole roof without any cut-outs, making the ventilating tiles completely superfluous. In the UK a cold roof means the water tank and pipework is at risk of freezing but the French prefer to manage without attic water storage so the problem does not arise. They do not have any water storage, preferring the tankless systems that are now becoming more common in the UK.

To summarise: I look for a nice steep pitch and a good overhang with no missing tiles, flashings or other defects. If the structure is uneven I look to see if this is related to the natural frame or due to over-loading. I check for any illegal tenants from the insect world or creatures that will eat your dinner if you let them. I want to see a good thick layer of insulation and good ventilation to remove moist air coming up from the living areas. If I see daylight from the attic I do not go into panic mode if the house is rural and hand-built. If there are no straight edges, lines or planes I enjoy the skill of the farmer-carpenter who managed to form a creditable "A" frame from Nature's timber supply depot, the forest. I do not 'slate' it just to be clever, excuse the pun. Remember that maintenance starts with the roof so check it out carefully or even better, get an experienced building surveyor to check it.
© Copyright 2008 Martin Quirke FRICS

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