Decking is a great way to update your garden for summer – it’s low maintenance, hard-wearing and gives you somewhere to sit and relax or enjoy alfresco eating in the warmer weather. It’s also a perfect solution for covering up an ugly patio or awkward areas where grass won’t grow.
Building a garden deck from scratch might not be the right first project for a total DIY newbie, but you certainly don’t have to be a construction expert, either. In fact, with the right tools and instructions, a keen amateur can put up decking in a weekend. Read on for our simple step-by-step guide.
Before you start
Decide on the deck’s location. Will it be attached to the house or free-standing? Think carefully about the amount of sunlight and privacy available in the spot that you choose to site your deck.
Decide on the size of the deck. Think about everything you’re intended to use it for: does it need to be big enough for a dining table and chairs? Use an online calculator to work out how much timber you’ll need.
If the deck is next to your house, make sure it’s 150mm below the damp proof course, and remember not to cover up any air bricks.
Ensure the fall of the deck frame is 1:100, running away from the house to aid water run off. The fall ratio tells you how sloped the decking needs to be – 1:100 means that for every metre of length, the deck must slope downwards by 10mm. For instance, a two-metre deck should slope enough to be 20mm lower at the far end.
Ready to go? Read on for our expert guide!
You will need
- Tape measure
- Deck boards
- Drill and drill bits
- Spirit level and set square
- Exterior-grade joist 47 x 150mm x 3m
- Adjustable decking risers
- 150mm and 100mm timber drive screws
- 50mm joist hangers
- 30mm exterior-grade screws
- 64mm decking screws
Useful to have: Spade, heavy-duty landscape fabric, Gravel 10mm, safety glasses, dust mask, gloves, wood preserver
Preparing the area An existing patio or concrete base is a good solid foundation for your deck. If you don’t have, one you’ll need to build a base. If you’re laying the deck over lawn, you’ll need to dig out to a depth of 50mm. After that’s done, cover the ground with landscaping fabric and add gravel. If the ground is soft, place paving stones on top of the gravel to support the joists and help protect the timber against water ingress from the ground.
Assembling the frame First, gather all the necessary boards, fixings and tools to make sure you aren’t missing anything before you begin. Then cut your exterior-grade joist to the desired lengths needed to create the frame and move them into position. The frame should be at the required level before fixing, so place risers, paving slabs or treated offcuts of timber at 500mm intervals, then check they’re all aligned at the correct height with a spirit level. Also check the corners are square using a set square.
To join the frame, mark and drill pilot holes using a 6mm drill bit before fixing the pieces together with 150mm timber drive screws. If you are adding a fascia board later, it’s best to countersink the screws.
Adding internal joists To work out how many internal joists are needed to brace the frame, measure 400mm from one corner, along the joist and draw a mark. Then from that mark, measure 400mm intervals along that side. Line these measurements up with marks in the same positions on the opposite side of the frame. Measure and cut the internal joists to size.
Lining up the joists Line up the first internal joist to the frame and position it so that the centre of the joist lines up with first the 400mm mark you drew earlier. Both ends of the joist need to be flush with the frame, so you may need someone to help you. Attach joist hangers to the joist.
Securing the internal joists Use a set square to extend the 400mm guide mark down onto the face of the outside plank. Using this line, measure 40mm up from the bottom and 40mm from the top and mark two pilot hole guides. Then drill countersink holes. A countersink is a tapered hole drilled with a wide outer portion to allow a screw to sit flush with, or below, the surface of the wooden board. Then use 100mm timber drive screws to secure the joist. Repeat for all joists
Tackling obstacles If you have an obstacle, such as a drainpipe, create a mini frame to go around it using offcuts. Mark where the mini frame will sit on the main frame then cut the section out before securing the mini frame.
Laying the deck boards Its best to pre-drill all holes with a 2mm bit to prevent damage or splitting later on. Always screw into the second groove from each side. When you’re screwing the boards in place, use the 64mm decking screws and secure both ends first, so the board remains straight. Once the ends are secure, work your way along the board, fixing the screws into the pilot holes.
Spacing the boards Make sure you leave a gap of between 5mm and 8mm depending on your preference, between each deck board. To make sure this gap is always the same, use an offcut of timber cut to size
Adding fascia boards If you wish, you can add fascia boards on the sides of your deck to create a neat finish.
Once the deck is finished, apply a decking stain or protector to the timber, these come in a variety of colours, as well as ‘wood’ and clear finishes. They’re formulated specifically to protect the surface from the weather and mould growth.
Each spring, clean off any leaves and dirt with a broom, then use a power washer to remove ingrained dirt that has built up over the winter.
If there are any stains, use sandpaper to remove them, using sandpaper with grits no rougher than 60 or 80, and abrade in the direction of the grain for the best results. Then dust off with a brush and clean the surface with methylated spirits. Allow it to dry before treating with it decking stain or protector to keep it looking great.