Garden Outdoor

Building Ground-Level Decking

lay decking on soil

Learn how to lay decking on soil, at ground level. Building ground-level decking is by far the easiest option if your available space is flat and sound enough to take it. There are no real foundations to create, no posts to fix and you won’t usually have to worry about creating steps or balustrades. It could potentially even be taken with you when you move house! If you are organised and plan it well, there is no reason why one person could not finish this type of deck in a single day.

This guide is based on building a square or rectangular ground-level deck.

Building Ground-level Decking

As mentioned, building your own decking isn’t the easiest of DIY jobs, and will definitely test your skills if you haven’t worked with wood very much before. But with this guide, a bit of careful planning, and as long as you take your time, it is definitely a project almost anyone can complete well.

Creating the Decking Frame

Check your measurements and cut all of the bearers you need to create the outer frame for the deck. Lay all four pieces out flat on the floor, in their correct positions, and fix them together using butt joints at the corners.

You should use screws at least 150mm long to fix the bearers together, and at least two for each corner. Measure diagonally across the frame (both directions) to make sure that it is square and then nail a timber batten diagonally across one of the corners to hold it temporarily to shape.

Measure and mark off points at 400mm intervals along two opposite sides of the frame. These will be the positions of the additional bearers that will create the frame. These extra supports will make the frame more rigid and support the decking boards.

If you are using decking tiles, adapt the width between the support bearers to match the width of the tiles.

Check the gap between the two sides of the frame you just marked and then cut the number of support bearers you need. Position the supports at their marks and fix them in place using 150mm screws. Your frame is now ready to be positioned onto its footings.

Preparing the Site for Decking

If you are building your deck over grass or soil, you will need to prepare the ground before you start. If the deck is going to sit on flat concrete or an area of paving slabs, no footings or foundations will be needed, but you may need to use some thin timber off-cuts to pack out one or more of the corners to make it completely level.

1. Using a tape measure and a handful of wooden pegs or stakes, mark out the area of the deck on the ground. Use the pegs to show where any and all corners will be, and then tie the string between the pegs to give you a guide for digging out the area. If you are planning a perfectly square or rectangular deck, make sure you measure across the diagonals to ensure the corners are square.

2. If building your deck over a lawn, use a straight-edged spade to cut through the turf layer and then divide the area into strips. Roll up the strips of turf and move them to one side. If you are building over an area of rough soil, remove any large stones and flatten the area using an old plank or similar. If you are building a ground-level deck, this stage is much more important and the area should be levelled accurately and checked using a spirit level laid on top of a plank.

3. If the area is well drained and does not suffer from being too damp, all you need to do now is lay down a sheet of a weed-proof membrane (cut to be very slightly larger than the cleared area) and then cover this with a 40-50mm layer of gravel.

If the area is not well drained, or if you simply want to give the timber deck frame something a bit more solid to sit on, place paving slabs at all of the corners and at intervals along the middle of the deck area. These can sit on top of the gravel base and will act as basic foundations for the frame. Use a long spirit level across the gap between the slabs to make sure they are all level and at the same height. If not, tap them down or add more gravel.

An alternative method is to remove the topsoil or turf, place the slabs at the corners and where they will support the middle bearers, and then mark around them with a trowel or other sharp point. Remove the slabs and dig out a further 25-30mm of soil beneath where they were sitting. Fill this hole with fine gravel and flatten it to the level of the surrounding soil. Now lay the slabs back onto their new beds, lay a weed-proof membrane between them, and cover this with more gravel up to the level of the slabs.

4. Move the frame into position on the slabs (you may need help to do this) and make sure that it is sitting evenly and not rocking when you stand on it. Your decking frame is now ready to start taking the decking boards or tiles.

Fixing the Decking Boards

Fixing the decking boards accurately and evenly is the main thing that separates the building of a nice deck and a stunning deck. Cut the boards carefully, measure and check your measurements and take your time. It is far better to spend an extra day finishing off your deck than rushing it and making a mess of it. Cut several boards at once and paint the cut ends with preservative before you fix them to the frame.

– Fixing the First Boards
The decking boards will lay at a right angle to the supporting bearers. Starting at the edge of the frame furthest away from the wall (if the deck is next to the house), lay the first board along the edge of the deck. Make sure that it is flush with the face of the frame. Use appropriate length decking screws to fix the board to the frame at each bearer, positioning the screws in one of the grooves if you are working with the textured side up.

There should be a gap between each board of between 3 and 10mm. Find a few offcuts of wood at the required thickness and use these to maintain the gap between each board you lay. Continue to lay boards, taking care to make sure the ends line up until you have boarded all the way to the wall.

– Finishing the Deck
The final board probably won’t fit exactly in the final space, so you will need to trim a board to fit. Measure the gap that remains and transfer the measurement to a decking board. Make sure you take into account the gap between the boards. Trim the board to fit and paint the cut edge with wood preservative. Lay this final board in place and fix it using decking screws.

To complete your ground-level deck, attach some fascia boards along the visible edges to cover up the bearers and cut ends of the decking boards. The fascia can simply be square-edged treated timber that matches the rest of the deck. Screw the fascia boards to the bearers using deck screws. The corners should be mitred to give a professional finish.