A shed is a must-have for every budding handyman (or woman). It’s a space to store all your tools, materials and other DIY essentials so they are not causing havoc inside the house. It’s a place to crack on with jobs out of the rain. And, let’s be honest, it’s a place to escape into your own little world from time to time.
A shed can also present a fantastic DIY project in its own right. Without being too tricky, erecting your own shed from scratch is still a good test of skill and patience. It’s a job that is best broken down into stages – laying the foundations, installing the base, building the frame and walls, and then adding the roof.
In this article, we’re going to focus on the last of these – roofing your shed. This is worth pulling out and considering in its own right because it may end up being a job you do more than once.
The roof is, of course, critical to protecting both your shed and everything you keep in it from the elements. But it is also particularly vulnerable to the worst the weather has to throw at it, especially high winds.
While a well-made shed roof should last years, you just can’t legislate for hazards like galeforce winds loosening rafters, flying debris punching holes in the felt, or even falling branches and trees crashing through the structure.
So if you ever do find yourself having to stick a new roof on your shed, or you want a detailed breakdown on how to finish your shed-building project off with the all important roof, here’s everything you need to know.
Decide on the roof type
There are two basic choices as to the type of roof you can put on your shed – a pitched roof or a flat roof. A pitched roof is the type that has two sides angling down in opposite directions from a central apex. A flat roof is, well, flat.
A flat roof is easier to install but a pitched roof offers better rain protection. To build a flat roof, all you have to do is fit rafters running horizontally across the framework of the walls, and then board and felt it on top. But you risk water pooling, which will shorten the length of time your felt will remain waterproof for.
The only way to prevent this is to angle a flat roof in one direction. If you are working on an existing frame, you can do this by adding a length of timber to one side of the frame before installing the rafters.
A pitched roof is much superior for water run off, but takes a lot more work. Instead of just laying rafters straight across the wall frame, you have to build a series of triangular frames.
Plan your roof design
Whichever type of roof you choose, it’s important to plan out your design before you start. There are a number of criteria it has to meet. The frame of the roof has to be strong enough to support the boarding and felt, you want to protect the walls of the shed from water as well as what’s inside as far as possible, and you have to comply with planning rules.
For example, a shed only counts as ‘permitted development’ (i.e. you don’t need planning permission) if it is under 2.5m high. If you choose a pitched roof, you therefore have to be careful with the angle of the pitch. In practice, the only way to keep a shed roof below 2.5m is to have a relatively shallow angle of rise.
The strength of the framework will depend in part on the number of rafters / truss frames you use, as well as the materials you choose and how well you piece everything together. Don’t be tempted to take a shortcut by laying too few – a maximum spacing of 600mm / 24” is the standard industry recommendation.
Finally, to prevent rain running straight off your roof and down your walls (which will speed up rot setting in), your roof needs to overhang the walls. This means your roof frame has to be built to ‘stick out’ both over the eaves (sides) and gable ends (front and back). Allowing a 300mm / 12” overhang is a minimum guide.
With the eaves, this is a case of simply measuring the trusses so they extend beyond the side walls. It’s a good idea to attach a batten to the end of these cross beams as this will help with felting (see below). To create an overhang at the gable ends, you will need to attach short battens pointing forward (or backwards at the back), and again cap with lengths of timber across the ends.
Board and felt
Once you have planned out and then installed your roof frame, it’s time to board and then felt your roof. This is a critical stage, as this will ultimately determine how water proof your shed is.
Start by calculating the surface area of your roof. On a flat roof, this will be a single area, on a pitched roof two (one for each ‘slope’). Buy or cut pieces of plywood to fit and then measure and mark fixing positions (i.e. where the trusses will be once the board is laid on top of the frame). Careful measurement and marking is important so you get a true hold when you screw the board down and don’t risk splitting the rafters underneath.
Next, cut your shed roofing shelf to size. This should be larger than the area of the board so you can tuck the felt underneath, which both creates a neater finish and makes everything more water proof. Allow a minimum of 50mm horizontally to tuck under the eaves and 75mm length ways to tuck under the gable ends.
Only fit roof felt when the board underneath is dry. Lay the pieces over the board so there is enough of an overhang to cover and tuck under the board. This is where having lengths of timbers attached to the ends of the rafters comes into its own, as you can tack the roof felt to this easily. For a secure and neat finish, you can attach a fascia board over the top of this, too.
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