How to build a basic ground-level deck

Decking is becoming an increasingly popular feature across many of our gardens and outdoor spaces, and it’s no wonder. As a highly dynamic and flexible feature, it can be used for a great variety of purposes, and for small or spacious gardens alike.

From simply sprucing up your garden and adding depth and character to sections of the landscape, to creating space for garden furniture, children’s play equipment and even a hot tub, you can adapt a deck to suit your needs.

When it comes to the variety of decking timbers that are available, you are spoilt for choice. All vary in colour, price and require different levels of maintenance, giving you the option to find a deck that suits your budget, lifestyle and exterior design.

Depending on the size and type of timber chosen, decks are relatively cost-effective to install and when well maintained, will endure all weathers for years to come.

You don’t necessarily have to call on the help of a carpenter to install your deck. In fact, laying a deck is most certainly a DIY project for someone who is willing to do their homework and give it a go. With the right tools and materials, laying a standard 2×2 metre deck is achievable in a day.

We’ve put together a guide on how to build a basic deck on the ground. Of course, decks can be built in all shapes and sizes to accommodate the landscape of a garden. This basic guide sets out to demonstrate the general approach and the skills, techniques, tools and materials required to build an attractive and long-lasting ground deck.

Materials:

• Decking boards (of your choice)
• 6×2 (150mm x 47mm) pressure treated timber
• 4×4 (100mmx100mm) timber posts
• 6mm wood screws
• Weed membrane
• 10mm shingle or scalpings
• Timber Cut End Preserver
• Concrete blocks (flat concrete paving slabs or breeze blocks are ideal)

Optional

• Building Sand or ballast
• Cement

Tools:

• String or stringline
• Wooden or metal pegs
• Shovel
• Tape measure
• Pencil
• Panel saw or hand saw
• Square
• Drill driver
• Spirit level

Step 1: Decide where you want to put your deck

It sounds obvious, and you’ve probably got an idea of where you want your deck to be positioned, but take some time to consider a few factors:

Sloping ground: The quality and gradient of the ground below the deck. A deck can be installed on a concrete surface, such as a patio or onto grass. Consider how you’ll need to prepare the ground before getting to work on installing your decking.

Privacy: How will the new deck affect your and your neighbours’ privacy? Will the decking mean that you can see directly into your neighbour’s garden and vice versa?

Sunlight: To what extent the deck will be exposed to sunlight? If your decking will be predominantly shaded, you will need to plan for treatment and removal of algae to preserve the timber that is exposed to more moisture.

Trees: What pre-existing plants or trees will you need to work around or remove? Are there roots that are affecting the quality of the ground? You may need permission to cut down trees.

Size: The size of your decking will impact what’s on your decking shopping list and the quantity of materials that you will need to gather.

Step 2: Prepping the area

Measure and mark

Tip: If you are building a square deck, you can also check that all sides are of equal length by measuring diagonally from corner to corner. The diagonal length from each corner should be equal.

Create an even surface

If the ground is particularly uneven, take some time to level out the ground. If you are laying your deck on a grass area of vegetation, dig away approximately 500mm within your marked out area. If you want your deck to be level with the ground, you may have to dig a little deeper to accommodate for the depth of the deck.

Laying sand and even cement will also help you to create an even surface. Ensure that you have a very slight gradient, so that rainwater and moisture can run off the surface.

Important: Don’t forget to check for cables and pipes before digging. This can be done with a metal detector.

Step 3: Construct the deck frame

Measure and cut

Once you are happy with the shape and size of your marked-out deck, re-measure the sides, corner to corner. This will give you the lengths of each side of the decking frame. If the deck is square, all lengths should be the same.

To create the frame, take a piece of 6×2′ timber and use a tape measure and pencil to measure and mark out your timber length. Repeat this for all four frame sides.

Use a panel saw to cut your four pieces of timber to length and treat all cut ends with  Cut End Preserver.

Assemble

Tip: You can then use a builder’s square as you go to check that each corner has a 90-degree angle.

Step 4: Raise the deck

You will need to raise the deck off of the ground so that it sits flush, or slightly higher than the ground around the deck. To do this, you need to fix four blocks (a block on each corner) to the frame to raise it off the floor. These timber blocks will then be positioned on top of concrete blocks, or slabs.

Cut your blocks to the desired height

Important: Don’t forget to treat all new ends with Cut End Preserver.

Align and screw the blocks into place

Once all four blocks are cut, one by one, place a block into the inside corner of the frame.

Ensure that the block is flush with the top of the frame before screwing from the outside of the frame into the block. Use two screws per frame corner face, in total using 4 screws.

Repeat this in all 4 corners.

Protect the blocks from ground moisture

You need to ensure that the timber blocks are not exposed to ground moisture as over time this will damage and rot the timber, causing your decking structure to become unstable.

Place a concrete block, such as a breeze block or paving slab under each corner block. It’s important that these blocks or slabs lay flush to the ground and do not wobble.

Tip: You can provide extra stability by prepping the ground with sand and even using concrete to even out and secure the concrete blocks or slabs to the ground.

Once all four blocks have been placed onto the concrete blocks, use your spirit level to check that the frame is level on all four sides. If uneven, adjust accordingly using the techniques suggested above.

Step 5: Keep weeds at bay

Lay a weed membrane

If you are laying a deck on a non-concrete base (i.e. over the top of grass, gravel or soil) you should have already removed any vegetation that would be growing under the deck.

Lay a weed membrane around the inside of the decking frame, covering all exposed ground. You could overlap the edges for extra protection.

Cover the membrane in shingle

Scatter 10mm pea shingle over the top of the membrane to hold it down.

Step 6: Install the joists

The joists run in parallel and are attached either vertically, or horizontally from one edge of the deck frame to another. They provide support to the deck.

Decide which way you want your decking to run

If you want your decking timbers to run vertically, or towards you, joists need to be fitted horizontally. If you want your decking timber to run from left to right, or horizontally, joists need to be fitted vertically.

Measure out the spacing between joists

The number of joists that you will need will depend entirely on the size of your deck. We would recommend that joists are spaced no further than 400mm apart.

To find out how many joists your deck will need, measure the inside length of your frame, in the same direction as you want to fit your decking boards.

Once you have this inside length, divide by 400mm and round up to the nearest whole number. This will tell you how many joists you need to fit inside of the frame.

Now calculate how far apart your joists need to be spaced apart by diving the inside length by the total number of joists needed (the whole number).

Mark out where the joists will be positioned

Step 7: Provide additional support to the joists

To prevent the decking boards from bouncing when bearing weight, you need to provide additional support to the joists.

This can be done by creating a block, as you did with the corners of the frame. You will need to space these support blocks a maximum of 1 meter apart along the joist length. For small decks, two blocks would be more than adequate, but don’t forget to factor in additional blocks if you are creating a larger deck.

Mark out, measure, cut and screw the additional support blocks

Step 8: Install the side decking

The decking process starts by installing the side decking. This is positioned around the edge of the decking frame.

Measure the outside frame

Measure the outside length of each side of the frame. Use your measurements to cut the four pieces of side decking to size. Don’t forget, you can use more than one cut of decking timber for longer lengths.

Align your decking to the side of the frame. Ensure that each piece of decking is flush with the top of the decking frame.

Use countersinking screws to fix the side deck to the decking frame, fixing with two screws roughly 500mm apart.

Top tip: you can make the cutting lines with a square to get a straight edge.

Step 9: Lay the top deck

Measure, cut and screw decking boards down

Step 10: Treat the deck

Since you have put all of the hard work into building your ground-level deck structure, you’re going to want it to last.

Treat decking preservers

Using an oil-based deck preserver will help to maintain the decking timber. You can also stain or paint the timber, depending on your desired finish.

Sweep and clean

Keep your deck clear of moss and debris by sweeping and hosing down every few months. If your deck is in a particularly shaded area and likely to be prone to moss damage, you may also need to jet wash the deck before treating. This can be done one or two times a year.

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