The short answer
Re-roofing a farm building starts with finding out what is on it. Many older sheds carry asbestos cement sheets, and HSE says to presume asbestos in a farm building put up before 2000. After that come the new sheet, the rooflights, the gutters and the downpipes, and the planning of the work around stock, feed and machinery. A survey settles each of them.
Farm sheds around Taunton work hard and are often large, old and altered over the years. A new roof here is a planning job as much as a building job.
Find out what the sheets are first
Older barns, cattle sheds and general-purpose buildings often have corrugated roofs of one kind or another, and the covering may have been replaced bay by bay over the years. HSE's starting position for a shed, barn or unit dating from before 2000 is that it holds asbestos until a laboratory shows it does not, and that suits an old farm roof well, since so many have been patched over the years.
Why does this come before the sheet choice?
Because it fixes the method. Under HSE's scheme, taking asbestos cement sheets away gently is non-licensed work, and smashing them up substantially makes it notifiable. Either way the waste travels with a registered carrier on a consignment note. All of that shapes the access, the time on site and the price.
Fragility comes with it. HSE guidance A14 says AC roofs are always fragile, and a roof of mixed bays may include rooflights in several states of repair. Read about asbestos surveys before roof work, and about how asbestos waste is disposed of in our other asbestos answer. Our own survey is taken from safe positions, and the report photographs cover each bay in turn.
Choosing the new sheet
Three covering families cover most farm re-roofs, and each has a place.
Which sheet suits which building?
Profiled metal sheeting is light and quick to fit, and it needs fewer supports than heavier materials. Fibre cement sheets, now made without asbestos, sit close to the look of an old roof and are covered on our fibre cement roof sheets page. Insulated panels suit buildings that need to hold temperature, such as a lambing shed or a workshop, and are covered in insulated roof panels.
The supports decide as much as the sheet. Old purlins, the horizontal beams under the sheets, may be bent, rotten or spaced too far apart for the new sheet's span, and they are checked and replaced where needed. Overcladding is the alternative of laying new sheets on top of the old roof, which is covered on our roof overcladding page. Where the old sheets are asbestos cement, it can avoid breaking them, though it is not always possible, and the survey says whether it is. It also adds load to the purlins, which are checked first, and a heavier build-up can bring Building Regulations into the picture.
Rooflights and gutters
Rooflights in a farm building matter more than in most. They bring daylight into a big space and cut the cost of lighting, but they are also the commonest weak point once a roof ages.
Should the rooflights match the old layout?
Not necessarily. Re-roofing gives you the chance to move them if the old ones are badly placed, to size them to the new profile and to pick a type that suits stock and weather. They must match the sheet profile so they lap correctly, and anyone working on the roof, now and later, must treat them as fragile.
Gutters and downpipes deserve the same attention. Heavy rain falls on a large roof, so an undersized gutter overflows and floods the yard, the walls or the slurry stores. Brett Martin's guidance for rainwater gutters gives a fall of 1mm for every 600mm, and brackets need to sit at the right spacing for the load. Replacing sheets and keeping the old gutters often shortens the life of the new work, so they are looked at together.
Planning the work around the farm
A farm does not stop for a roof. Stock, feed, bedding and machinery all share the building, and the work has to be phased around them.
What do we agree before starting?
Which bays can be emptied and when, where the sheets and waste will be stacked, how vehicles reach the building, and how animals are kept clear. Dust, falling debris and noise all matter around livestock, so the farm gets a day-by-day outline of what happens where. The site is left tidy and the waste taken away, and the yard is swept for loose fixings before stock goes back in.
If the look of the building changes, or it sits in a protected setting, ask Somerset Council's planning team before ordering. Questions about Building Regulations on a larger re-roof are best put to your building control body before you order. Our survey covers the roof, supports, rooflights and gutters together, and a single written price follows it. The commercial roofing page covers the wider service. Send the farm's location, the building's approximate age and a few photos of each side.
More on farm roof work
Can the work be done in sections while stock stays in the shed?
Often it can, if the building is divided into bays and the stock can be moved away from the section being worked on. It depends on the roof's condition, the access and whether asbestos is present. Tell us during the survey how the building is used, and we will set out the sequence in the plan.
Do old fibre cement sheets always contain asbestos?
Not all of them, but the eye cannot sort the two. Sheets laid before 2000 may contain asbestos, and sheets made since are asbestos-free fibre cement. HSE's advice is to presume asbestos in older buildings until a laboratory sample says otherwise, and a survey is the way to obtain one.
The full picture: Commercial roofing in Taunton ยท More short answers