Before you get started
Decking is quicker to install than paving, and building a deck is straightforward. The deck will be long-lasting and durable if you use pressure-treated timber and screws that are designed for the job.
Building regulations can be an issue with even small-scale decks. It is worth checking with local planning authorities before you start any construction work. Keep neighbours informed if you decide to build a substantial structure and be prepared to alter your building plans if they object.
Deciding on the location is important: do you want a sunny or shaded location and is privacy a requirement? Decks built in permanent shade can be affected by damp and algae growth, so be prepared to clean and treat these once a year to preserve the timber. Avoid very wet areas completely.
It is essential to plan your deck to scale on paper. Be as accurate as possible with measurements and bear in mind the size of the deck boards you plan to use. Designing a deck carefully will limit cutting, and board or bearer wastage.
Plan the deck so that it slopes very slightly (a 1:80 fall is sufficient), and use fluted deck boards that run in the direction of the slope; this will aid rainwater run-off, meaning the deck is less slippery and less prone to algae build-up.
There is no need to remove an old patio or concrete base where you plan to lay decking. Instead, use it as a solid foundation for a deck of any shape or size. If the bearers (wood supports that will bear the weight of the decking) are not level, use thin offcuts of treated timber to level them, before laying the deck. On soft ground it is possible to make a simple foundation of paving slabs bedded on gravel to support the deck and preserve the timber. Before you start laying this foundation, remove any vegetation and grass and lay a landscaping fabric. If you have a sloping garden, or areas of the garden are difficult to use, garden decking is a quick and practical solution tomake these areas accessible.
Following your plan drawing, mark out the deck area with pegs and string line. Remove turf inside the area and 5cm of topsoil. Level the ground if slightly uneven, remembering to allow for the slope of 1:80. Make sure the ground is firm.
Place paving slabs at each corner and midway along where each bearer will be, including the edges, or every 1.5m if you are laying a larger deck.
Mark the area around each of the slabs with a spade and set them aside. Remove a further 2.5cm of topsoil from the marked areas.
Replace the soil you have removed from beneath each slab with a bed of gravel. Reposition slabs, checking that all are level and firmly bedded.
Roll out landscape fabric and cut and trim to fit around each slab. If you need to overlap the membrane, do so by at least 10cm.
Cover the membrane with a thick layer of gravel. Spread it out evenly with a rake so that it is level with the top of all the slabs.
Mark, cut and lay out the outer frame first using decking bearers. Ensure the frame rests flat and is totally supported.
Join the frame at each corner using two external grade 150mm (6in) screws. Use a spirit level to make sure the frame remains flat.
Its corners should be square, and you can check this by measuring the frame’s diagonals; they should be equal. Adjust the frame if it is not square.
Before fixing intermediate bearers inside the frame, check your intended layout of boards, as the pattern will affect spacing and number of bearers needed. For example, double bearers will be needed for some chevron styles, as above. Each bearer will need a paving slab to support it at least every 1.5m.
Now mark, cut and fit the intermediate bearers, with a maximum spacing between bearers of 500mm, checking they are flat with a spirit level as you go.
Next lay you deckboard on top of the frame and predrill all fixing points with a 2mm bit to prevent boards from splitting.
If you countersink all drilled fixing points you will get a neater, smoother finish. Sand all cut ends of timber to avoid splinters developing too.
When you have predrilled the holes, fix the boards to the bearers with two 64mm decking screws to each bearer underneath.
Keep even spaces between adjacent boards. An offcut of wood is ideal. Once each board is secured, move the spacer to the next position.
You can trim boards at the end to make a straight edge. Mark the timber using a spirit level or timber board, and use a jigsaw to carefully cut the overhanging deck boards.
To create a curved edge, mark out curves using a string line in an arc or with a piece of timber fixed to create an arc. Bear in mind that unsupported decking cannot be more than 150mm away from a bearer.
Finally, add deck boards around the edges to frame the deck and finish it neatly.