Garden Decking DIY Tips

Garden Decking types

Garden decking can be a confusing task- From working out the size, how many beams you need as well as the base. Luckily this guide should help with any confusions to get you started on your new garden deck.

There are two main types of decking:

  • Decking tiles: These are ready made squares to give you a great alternative to the traditional decking boards. Made from pine, hardwood and composite materials, we offer a range of styles and sizes ranging from 30cm x 30cm to 100cm x 100cm to allow you to find the decking tile that would suit your garden. Easy to install, see our Decking Tile Range
  • Decking boards: The traditional way to build a decked area, our decking boards are available in Spruce, Pine, Hardwood and Larch in a range of sizes. These boards tend to be installed on a slightly raised base or rest on top of a flat base. See our Decking Board Range for some inspiration.

In this post you will see some examples on using decking boards to create a decked area for your garden. From advice on placement to assembly tips, this post will help anyone build their own garden deck.

Advice before ordering your supplies

  • Think carefully about the size of your deck. For example, if you’re planning to build garden decking for a dining table large enough to seat four people on.. Lets also add a sun lounger on the decking too, you will need to consider a deck size of 5m x 4m.
  • Start off with some grid paper and start a sketch of your garden, or the area that you want to build the deck on. By working out a reasonable scale onto paper, you’ll have a guide for calculating the materials you’ll need.
  • Consider the space needed between each of the decking boards, we recommended around 5-10mm space between each board. However if the decking board is wet you can reduce this gap by a few millimeters, or if you are installing this on a hot day, make sure to increase the space to allow the natural expansion of the timber to occur.
  • Be prepared with the tools needed for installation. To build decking you will usually need: a power drill, hand saw, a rubber mallet and a knife suitable for cutting weed control matting or similar materials.
  • Be safe when installing your deck, keep children away and wear the appropriate shows and gloves to protect yourself from splinters and other accidents that may occur during this process.

Calculating materials

Square Posts

It’s best to start this out with a sketch of your garden or the area that you’re planning to build your deck on, using graph paper. The posts have to be between 40cm – 50cm appart, making sure that the frame beam starts and ends on a post with a maximum of 10cm overhang. We recommend ground posts of 1 meter in length.

Weed Control Matting

Perfect for letting through water but suppressing weed growth, Weed Control Matting is a necessary material needed for your garden decking. Available in a large range of widths, you’ll need to work out the length needed for your deck guide with a 20cm overlap on each side.

Frame Beams

Framing beams are available in a range of sizes, thicknesses and materials- Typically we suggest to keep the frame material the save as your decking boards. So if you’re opting for a hardwood deck please look into using hardwood beams for your frame to prevent any difference in how different woods may expand or contract compared to others in wet or dry conditions.
Work out the beams needed with the 40cm distance mentioned with the square posts, with a maximum 10cm overhang overall.

Decking Boards

Starting from the popular 14.5 cm wide plank width, you’ll need 7 linear meters of plank floor per square meter. To determine which board length you need, take the width of your deck into account. For example, you can use the 5m length boards with a deck up to a maximum of 5 meters wide. At 5.20m you can choose the 300cm and 240 cm length variants. If you have seams, always have the head seams offset, this way you’ll have a more aesthetically pleasing deck instead of all the seams in a row in the middle.

Always keep in mind that there is sufficient space between the boards, do not underestimate the movement of wood! With hardwood planks 14.5 cm wide, maintain a minimum of 8 mm between them and with softwood planks at least 1 cm.


To work out the number of screws needed, take the total number of linear meters and divide it by 40cm, then times it for two so that you will have two screws every 40cm in each deck board. For example, for a 5.20m x 4m deck you will need:
5.20(width) x 4(length) x 7(number of frame beams) / 0.4 x 2 = 728 screws.
Our Decking Screws are available in packs of 200 screws.

Step by step guide

1. Sand bed substrate

Sand bed substrate

Dig up around 20cm of soil in the area that you plan to build your deck if the ground is hard- Then cover the area with around 10cm of white sand. If your area is on a hard surface or in a wet and damp area, we’d advise to lay some drainage in this step.

2. Placing posts

After prepping the base you can start to plot out where your posts need to go according to the calculations done earlier. An auger would be one of the easiest ways to dig out these holes, then place the posts around 90-100cm deep into the ground- Going this deep will help prevent the posts from rising in cold and frosty weather conditions. Provide approximately 20 cm of ventilation space under your deck.

Place the posts in a row a maximum of 50 centimeters apart and the beams mutually 40 centimeters apart, the beams must lay at a maximum of 30 cm apart from each other.

3. Laying the Weed Matting

Weed Control Matting

As mentioned earlier, using a weed control mat will ensure that no weeds will grow between your decking boards. Cut a cross on the posts with a knife to allow a snug fit, also make sure that the ground cloth is about 10 centimeters under the frame beams so that your deck can be well ventilated.

4. Fixing the frame beams

Now the frame beams (also called cross beams) can be mounted on the square ground posts. Never mount the beams on top the posts but on the side, this gives more strength to the deck base than fixing it to the top point of the post. Position the beams to go on the outside of the rows, as shown in the diagram above.

Keeping the beams nice and level will help this process. In this example M8-120mm lock bolts were used to secure the beams to the square posts, if you are using softwood as your material then do not pre-drill your beams however, if you are using hardwood then you can pre-drill the beams to help you.

5. Screw on the decking boards

Now it’s time for the tedious part, the mounting and screwing the decking boards onto the beams you just installed. lay the first board 2cm from the wall to allow expansion to occur without damaging the wall or your deck. As mentioned in the previous step, you can pre-drill your hardwood board but we advise against doing this with if you have a softwood deck as this will affect the grip from the screw.

We recommend to use between 2-3 screws every time your decking board meets one of the framing beams, making sure that the screws are not too deep into the wood to prevent the screw head from breaking off when it expands during the winter. We recommended around 5-10mm gap between each board. However if the decking board is wet you can reduce this gap by a few millimeters, or if you are installing this on a hot day, make sure to increase the space to allow the natural expansion of the timber to occur.

Create an aesthetically pleasing deck by staggering the decking boards, as shown in the example above. Only saw off any beams and planks that are too long. You can finish the sides of the deck with a standing board or a special sideboard.

6. Cleaning

Decking Cleaning

Finally, just sweep the splinters off the platform. You are now ready to place your garden furniture on your deck. Avoid color differences by regularly moving your patio furniture and/or storing it in the winter.

7. Maintenance

In theory, your deck doesn’t require much maintenance. Over time your wood will age as expected, if you are using hardwood then you can expect the colour of your deck to turn into a silver grey. If you want to preserve the rich colour of your new deck then you can use a Decking Oil twice a year using a block brush. The treatment of your deck can be left for a few weeks after the installation to allow the decking boards to settle.

We do, however, recommend keeping your deck free of algae, dirt and water (snow and black ice) so that the risk of slipping is small, keeping the grooves clean with a sturdy broom ensures a better anti-slip effect and clean finish.

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