There is lots of choice when it comes to garden office roof coverings, the choice you make will be dictated by the shape of the roof, personal taste and cost.
Flat Roof Coverings
Up until a few years ago your only option for a flat roof was a hot felt roof where bitumen felt was laid over hot bitumen, these worked well but were not the most attractive of roof coverings and they had to be replaced every 10 or 15 years. Today we have more options, the most popular option being an EPDM rubber membrane. EPDM is laid in whole sheets so there are no joints which could be vulnerable to leaks, EPDM has been used on commercial buildings for years and has a maintenance free life span of several decades.
Single Ply Systems
Single Ply roof systems are light weight roof coverings made up of layers of insulation and PVC membranes which are bonded together, any joints are heat sealed to create a continuous water tight seal. This type of roof covering has a life expectancy in excess of 30 years and is recyclable at the end of its useful life.
Composite roof panels are becoming popular on garden offices; they are light weight panels which need little support so a complex roof structure does not need to be created. The interlocking sheets consist of a sandwich of metal skins and rigid insulation. The external skin is normally profiled to shed water easily and coated for durability; the interior is normally white and forms the ceiling of the garden office.
Another option on flat roofs is a living roof; sedums are a popular choice on living roofs because they require little maintenance and only require a light weight substructure. Plants can be chosen to flower in sequence providing year round interest. Grass is another option but will require a trim so consider how easy it will be to get onto the roof of your garden room and maintain it! One of the prettiest living roofs is a meadow mix containing all the varieties you would expect to find in a summer meadow. Meadow mix living roofs have more colour than sedum and grass roofs, they also have more height meaning the planting is visible from ground level, and a meadow roof will require some maintenance. New designs for living roofs are appearing all the time, at the RHS Chelsea Flower Show 2011 a show garden featured a roof planted with lavender – the colour was striking against the timber cladding and the height of the plants gave the roof a 3D feel and looked great from above and from ground level – a trend we expect to see on garden offices before long.
Pitched Roof Coverings
The entry level roof covering for a pitched roof is asphalt shingles. Asphalt shingles are a strip of bitumen coated with ceramic chips; they are shaped to look like slates and come in a wide choice of colours and have a life expectancy of 25 years. Asphalt shingles are fixed onto a plywood roof deck which is fixed over the rafters, a torch is used to heat a strip of bitumen on the back of each tile; this melts and sticks to the tile below preventing the tile lifting in the wind.
Cedar shingles are a popular choice on pitched roof garden offices – they cost more than asphalt shingles as the material is more expensive and they take longer to install, but a cedar shingle roof looks great! When specifying a cedar shingles roof it’s a good idea to check that your supplier uses the fire retardant version. Cedar shingle roof start out a reddish brown colour, they have a life span in excess of 25 years. Cedar shingles are fixed into treated battens and should be fixed with stainless steel nails as the oils in the cedar can corrode other types of fixing, because of the way they are laid there are three layers of shingle at any point on the roof.
A tiled roof effect can be created on a pitched roof garden offices by using steel, stone coated shingles which have a life expectancy in excess of 50 years. Steel shingles come in strips which interlock to prevent wind uplift.
Slates can form a striking garden office roof but a slate roof is heavy so a sturdy roof structure is required to avoid the roof sagging. There are several types of slate from natural Welsh slates to synthetic imitations; your final choice will be dictated by aesthetics and cost. Ask your supplier to show you samples of the slate they use so you can look at the colour and pattern of the slate. Like cedar shingles slates are fixed onto spaced treated bitterns fixed into the rafters, a well tiled slate roof will last decades.
Clay tiles are another option on pitched roofs, like slates they are heavy so a strong roof structure is required. Clay tiles came in different qualities from handmade to machine made and each variety will have its own features. Clay tiles are very attractive roof covering with the different shades of tile creating a mellow finish.
Metal roof coverings have become a key part of creating contemporary pitched roof garden offices, the colour of the metal and the detailing of the joints are a striking modern feature in themselves. The four main metal roof coverings are zinc, aluminium, copper and steel. Zinc is either laid in its natural bright state or chemically weathered or powder coated if a coloured finish is required. Aluminium is a light weight roof covering but very strong, it’s normally powder coated and is available in a wide choice of colours to compliment any design. Copper has been used as a roof covering since Roman times and develops a distinctive green hue as it oxidises, copper can also be alloyed to create different colour finishes. Steel roof can create a very modern building and comes in several finishes from bright to brushed.
WOW – what a lot of choice, which will you choose? The next decision you need to make is the type of doors you want on your garden office, we will look at the options in the next part of this guide.