Although the ability to design and construct a timber framed house is probably beyond all but the most avid DIYer, constructing a small garden shed using similar principles is quite feasible, given a little bit of planning.

Consider the overall size of your shed and the location and sizes of doors and windows before you start. Make sure the sizes you choose are readily available off the shelf or that you have the skills and materials to make your own. Decide what sort of roof you want - flat or pitched - as this will affect the amount of material you need and the design of the gable walls. Sketch the layout, using graph paper to help with scaling. Draw a plan showing the position of each timber member, as well as elevations of all four sides. This will help you calculate how much timber you will need and visualise how the different components fit together. Order a bit more timber than you think you need so that you are prepared if your design evolves during the course of construction! If you don't have access to a van or trailer most merchants will deliver your materials for a nominal charge. Remember to order sufficient nails and screws, too!

The tools

Panel saw (for studs/joists/cladding)
Jigsaw or circular saw (for floor and roof decking)
Electric drill and bits
Hammer
Tape measure
Spirit level
Screwdrivers

Take care when measuring and cutting and take the time to square and level components. A little extra effort here will pay dividends in the long run.

The ground

Prepare the area on which your shed is to stand by excavating the entire area to a depth of 75-100mm (3-4") and levelling the soil. If the ground is soft, compact as necessary. Add 25-50mm (1-2") of sharp sand and lay dense concrete paving slabs in the sand. Take time to level the slabs as this will make subsequent work easier.

The floor

Make a perimeter frame of pressure-treated 100mm x 50mm (4" x 2") sawn timber and fix each corner using two 125mm (5") round wire nails into each section. Insert the nails at slight angles (called skew nailing) to stop the joints pulling apart easily. Fit joists of the same material inside the frame, spaced at 600mm centres, and skew nail. Locate the floor frame over the concrete base. The frame should be supported off the ground to prevent prolonged exposure to water. 

Fig. 1

Common bricks placed under each end and at mid-span of each joist should provide adequate support and allow ventilation. Ensure that the floor frame is level and square before fixing the floor deck of 18mm flooring chipboard. The chipboard should be laid with the long edges at right angles to the joists, with the end butt joints over the joists. Nail the decking down at 300mm (12") centres.

The walls

For a small shed the wall framework can be made from 75 x 50mm sawn timber vertical studs spaced at 600mm centres, with horizontal rails top and bottom (see fig. 2). These timbers don't need to be pressure treated as they should not become wet. Lay out the members on the ground and nail the sections together in the same way as the floor structure. Stand the first wall frame in position and temporarily brace it. Screw the sole plate down to the floor structure using 100mm woodscrews at 600mm centres. Adjust the frame until the studs are vertical (use a spirit level) and fit a diagonal brace on the inside to provide 'racking' resistance.

Fig. 2

Measure the length of the second wall so that it butts up to the first and construct the framework as before. For openings use double studs for strength at the sides of door openings and across the top of window openings. Cut studs for windows and fix horizontal 'noggins' to form the outline of the opening. Erect the second wall as the first, making sure both the studs and the plane of the wall are vertical. Screw the walls together at the corner using 100mm woodscrews at 600mm centres. Repeat for the remaining walls.

The cladding

The wall framing is now complete although at this point the structure will not be very rigid. Additional strength will be given by the cladding. Use pressure impregnated softwood boarding and make sure you use an exterior cladding profile that is designed to provide water resistance, such as shiplap boarding. Begin at the bottom and fix the first strip, with its tongue upwards, by nailing through the centre of the board to each stud.

Use a spirit level to check it is horizontal and only use a single nail near the middle of the board to prevent splitting with moisture movement. Use galvanised or stainless nails and cut the board so that joints occur over studs. Remember to treat cut ends with preservative.

Continue boarding all walls, ensuring joints are staggered. Finish the corners by fitting vertical battens at a right angle to each other to make an 'L' section.

The roof

Roofs may be of flat or pitched construction and this should be decided before starting work. In either case the construction technique is essentially similar. Note that flat roofs must be inclined at an angle of at least 5 degrees to encourage water to run off. For a pitched design the inclined members, called rafters, should be installed at the same centres as the studs and notched so that they sit comfortably on the top rail of the wall panels. The roof deck comprises a moisture resistant board such as exterior plywood nailed to the rafters, which adds strength to the whole structure. It is often easier to construct the roof as flat panels on the ground and lift them into place, although some assistance will be needed for this. Fix the roof panels to the walls by using metal cleats on the inside from the rafters to the wall panels (see fig. 3).

Fig. 3

The most common roof covering is bituminous roofing felt. Use two layers of glass-based felt fully bonded with SBS based cold set adhesive. A 125 g/m² base sheet with a 350 g/m² base sheet will last at least 15 years. However, ranges of corrugated plastic, corrugated fibre and bitumen boards are also available from most DIY retailers. For transparent roofs, polycarbonate sheeting also works well.

The windows

Although you can make a window from treated softwood mouldings, it is difficult to make it watertight and secure. A better solution is to purchase a factory prepared unit for the job.