How to lay decking

• Tape measure

• Pencil

• Spirit level

• Try square

• Combi drill

• Drill bits

  • 2mm and 6mm wood drill bits

  • Countersink drill bit

• Saw

• Paint brush

• Protective stain

• Chalk

• Pegs

• String

• Spade

• New decking

  • Deck boards or composite decking

  • Decking joists

  • Decking posts

  • Adjustable decking rises

  • Exterior decking screws

  • Joist hangers

• Landscaping weed control fabric

• 10mm gravel

• Paving stones

• Sand paper

Always put safety first when you take on a garden decking installation. Make sure you wear appropriate protective clothing. You need gloves, a dust mask, and safety goggles. Wear these whenever you’re cutting or sawing timber or applying preservatives and treatments.

A solid, level foundation is incredibly important for a long-lasting deck. Concrete is a great choice for laying decking on, and an existing concrete base or patio would be perfect. If you want to know how to install decking on concrete, start by measuring and marking out your required area using chalk.

You can also lay decking on grass, but you need to make sure you prepare the area properly first. 

• Mark out the space using your pegs and string. 

• Use a straight edge to cut the lawn edges. 

• Remove the turf and dig the soil out to a depth of 50mm using your garden spade.

When laying decking on grass, soil, or gravel, do the following:

• Cover the bare ground with landscaping weed control fabric. 

• Weigh the fabric down securely with your gravel or pea shingle.

• Place paving stones on top of the gravel to properly support the timber joists and preserve the wood. Use a spirit level to make sure these stones are all sitting on the exact same level.

If you’re wondering how to lay decking on soil safely, the secret is keeping your timber raised off the damp ground, so it doesn’t rot.

If your deck joins directly onto your house, you need to attach a wall plate. This anchors the structure safely. If you’re building a freestanding deck in the middle of the garden, skip straight to the frame building stage.

Step 2.1: mark the decking corner

Start by marking a vertical line where one end of the plate will sit. This will mark the corner of your decking.

Step 2.2: check the fit around a step or sill

If you’re building around a step or sill, check the design fits by taking an offcut of your deck board. Hold it in place beneath the step and mark the bottom edge.

Step 2.3: mark your wall plate guideline

From that line, drop the board down by 10mm to allow for natural timber expansion. Use your spirit level to draw a new horizontal line. This is your guideline for attaching the wall plate, so mark it across the proposed full width of the decking.

Step 2.4: cut your first joist

Next, cut your first joist to the required length. If you need to avoid any obstacles like a pipe, measure and cut the joist accordingly.

Step 2.5: mark the joist

Measure 100mm in from one end and use a set square to mark a vertical line down the joist.

Step 2.6: work out your pilot holes

Make a pilot hole 50mm down from the line you just made, and 50mm in from the bottom edge. Repeat this at 600mm intervals along the length of the wall plate.

Step 2.7: mark the other end of the joist

When you reach the other end, measure and mark another 100mm section.

Step 2.8: drill pilot holes

Drill all pilot holes using a 6mm drill bit.

Step 2.9: place the plate into position

Place the wall plate into position along your horizontal guideline. Use timber supports if necessary, and check that it’s level.

Step 2.10: double-check the deck’s fit

Before securing the plate, double-check that the deck board still fits beneath the sill.

Step 2.11: partially drill guide holes into wall

Partially drill guide holes into the masonry wall using a 7mm masonry drill bit. It’s best to ask someone to hold the timber in place for you while you do this.

Step 2.12: finish drilling holes in wall

Move the wall plate away and complete the holes by drilling directly into the wall.

Step 2.13: insert wall plugs

Push wall plugs into the drilled holes, gently tapping them in with a hammer. Reposition the wall plate.

Step 2.14: insert screws and washers

Insert 6mm x 100mm screws through the timber holes and hang plastic or galvanised washers on the ends. Use enough washers to build a 10mm gap between the brick wall and the timber wall plate.

Step 2.15: fix the wall plate into place

Fix it securely using a drill and driver bit.

A strong frame is the backbone of your deck installation. Here’s how it’s done.

Step 3.1: joining decking joists

If your decking is going to be longer than the decking joists, you’ll need to join two sections of timber together.

Step 3.2: measure and cut to correct length

Measure and cut the section you need to reach the required length.

Step 3.3: join the joists

Measure and cut a separate section of timber to 600mm in length. Mark its centre point at 300mm. Secure the three sections together on your workbench. Make sure the 300mm mark lines up perfectly with the join of the two joists.

Step 3.4: measure and mark joist guidelines

Measure and mark spots 75mm from each side of the join, and 150mm from each side of the join. Use a set square to draw straight vertical lines through these four marks.

Step 3.5: mark and drill pilot holes

Mark two evenly spaced pilot holes on each line you’ve drawn. Drill the pilot holes with a 6mm wood drill bit and secure the joists together using 100mm screws. If you’ll be using fascia boards later, make sure to countersink these screws.

Step 3.6: fix the decking frame into position

Now, move the decking frame into position. It must be at the correct level before you fix it in place. Use your adjustable risers, paving slabs, or treated offcuts of timber at 500mm intervals to help support it. Check it frequently with a spirit level and check that all corners are perfectly square using a set square.

Step 3.7: join the external frame together

To join the external frame together, mark and drill pilot holes. Fix two external grade 150mm timber drive screws into each corner. If some external corners are hard to access, secure the frame by drilling skewed pilot holes at a 45-degree angle. Fix these with 100mm external grade screws. Check again that the frame is fully level.

Internal joists provide vital stability when installing deck boards.

Step 4.1: work out your internal decking joists

To work out how many internal decking joists you need, find the centre spot of one of the external joists. Measure 400mm inwards from this spot and make a clear mark. 

Repeat this process so all your internal joists will be spaced at 400mm intervals. When you get to the final joist, it’s much better to have a narrow gap to the external joist rather than exceeding a 400mm gap.

Step 4.2: extending an internal joist

If you need to extend your internal joists, then follow the same method as for joining external joists, but this time use an additional 600mm block to sandwich the joist in place. Offset your pilot holes slightly so the screws won’t come into contact with each other.

Step 4.3: attach the joist hangers

Secure the joist on your workbench. Attach a 50mm joist hanger to each end using 30mm exterior screws.

Step 4.4: place the joist into position

Place the joist into position so the centre lines up with your 400mm spacer mark. The joist end must sit perfectly flush with the exterior frame. Either use packers to keep it in place or ask a friend to help hold it.

Step 4.5: mark your pilot holes

Use a set square to extend your 400mm marker down onto the external face. Make two marks on this line, 40mm from the top and 40mm from the bottom. These will mark the position of your pilot holes.

Step 4.6: drill the pilot holes

Drill the pilot holes using your 6mm wood drill bit. Drill countersink holes and secure the joists using 100mm timber drive screws. Repeat this process for the rest of your internal joists and always make sure the ends of the joists sit flush with the frame. 

If some parts of the external frame are hard to access, you can again secure the internal joists by drilling two skewed pilot holes on each side before securing with screws.

Step 4.7: secure the joists

Once the joists are in place, you can further secure them using joist hangers and 30mm screws. If you want to conceal the timber through the spaces between your deck boards, paint the top of the joists black.

Noggins are short pieces of timber that fit snugly between your internal joists. They provide essential rigidity to the decking frame. The width of each one is fixed by the width between joists.

Step 5.1: work out the position of the noggins

When measuring the joists lengthways to decide how many noggins you need, try to ensure the distance between them is never greater than 1200mm. To avoid having to skew any screws, it is best to stagger the positions of the noggins.

Step 5.2: position the noggins

Put the noggin in position so its top is level with the joist. Use packers underneath if necessary.

Step 5.3: mark the noggins for pilot holes

Mark the centre of the noggin’s position on each joist and use your set square to draw a vertical line. Measure and mark two pilot holes on each line, 40mm from the top and 40mm from the bottom.

Step 5.4: drill pilot holes

Drill the pilot holes before securing the noggin with 100mm external timber drive screws. Check that your frame remains level and that all fixings are incredibly secure.

Step 5.5: add extra support around obstacles

If your decking is going around an awkward obstacle, add extra noggins around it for additional support.

Now you can start laying decking boards on top of your sturdy frame. Always use structural, treated timber and screws specifically designed for the job.

Step 6.1: pre-drill holes

When you’re laying deck boards, it is always best to pre-drill all holes with a 2mm bit. This stops you from damaging or splitting the natural timber. Countersink all the holes and screws to achieve a smoother, professional finish.

Step 6.2: prepare for a fascia board

If you intend to add a fascia board later, your first deck board will need to overhang the edge slightly. You might have to adjust the position of your holes to make sure the board firmly secures to the frame.

Step 6.3: secure your first decking board

For the rest of the decking boards, try to screw into the second groove from the edge. Fix the board to the frame using 64mm decking screws. Repeat this at the other end of the board first so it is fixed straight, then work your way down the middle of the board.

Step 6.4: use a spacer to keep a consistent gap between boards

Use a suitable spacer to maintain a 5-8mm expansion gap between each decking board. Make sure the gap is even all the way along the length of each board. This gap allows for rainwater runoff and lets the wood expand and contract naturally over its life.

Step 6.5: cutting deck boards to fit

If you need to cut a deck board lengthways to fit, do it either with a handsaw or a circular saw. Place this cut board in the area of the least through traffic. When sawing, use the 90-degree guide marker on your saw to make accurate cuts.

If you need to cut a deck board to accommodate a difficult obstacle, create a cardboard template first. Mark the saw guideline onto the wood, and cut it carefully with a jigsaw.

To finish your deck installation beautifully, you can add fascia boards to the exposed edges.

Step 7.1: mark and measure the fascia board

Mark your fascia board with a pencil line at 50mm from each end. Then, from the first 50mm line, measure out and mark lines at 600mm intervals all the way down the length of the board.

Step 7.2: place the fascia into position

Put the fascia into position against your frame. Use timber offcuts or packers underneath the fascia to keep it perfectly level. 

Using your marked lines, pre-drill guide holes into the second groove in from each side. Finally, secure the fascia board tightly to the frame using your 64mm decking screws.

Step 7.3: add lighting or railings

Finally, if you’d like to add lighting or railings to your decking, you can follow our step-by-step guides on how to assemble deck railings and how to install deck lighting.

Learning how to lay decking tiles is incredibly straightforward and very beginner-friendly. You interlock the deck tiles over a perfectly flat, solid surface. Because they sit directly on a firm base, they do not require you to build a heavy timber joist frame first.

In most typical cases, laying decking falls under permitted development, meaning you don’t need planning permission. However, if your decking is going to be more than 300mm above the ground, or covers more than half of your garden area, you should check with your local council first. We always advise checking local regulations before starting a large home improvement project.

Expansion gaps are absolutely essential when constructing timber decking. You need to leave a dedicated expansion gap of 5-8mm between each board. This gap allows for natural rainwater runoff and accommodates the natural expansion and contraction of the wood as the temperature changes.

Yes, an existing concrete base or an old patio makes a fantastic solid foundation for your deck installation. Before laying decking on concrete, you simply measure and mark out the required area directly onto the concrete. Then, build your timber frame on top, using adjustable decking risers if you need to level it out.

Your overall deck installation cost will naturally depend on the size of your space and the materials you choose. Taking the time to build it yourself using our sturdy treated timber is a brilliant way to keep your budget manageable. By doing the work yourself, you save heavily on professional labour costs while still achieving an excellent finish.