A sandpit makes a fun addition to the garden. Children can build castles and dig holes. A sandpit is a perfect way to introduce some seaside spirit to the back garden and they can be built in any shape or size to suit your outdoor space.
Here’s a Step-by-Step Guide
Step 1
Firstly, measure and mark four deck joists to a length of 1 metre. Repeat the process for another four joists measuring 1.05 metres (this extra allows for the overlap of the corner joins). These joists will form two square frames or ‘boxes’ that will sit one on top of the other.
Cut the deck joists to size.
Step 2
Treat all cut deck board ends with a decking end grain protector or wood treatment.
If these sawn ends are left unprotected, water will soak in leading to rot and decay.
Wear safety gloves and apply with a paintbrush following the instructions on the tin.
Leave to dry.
Step 3
Make two marks with a pencil on each end of the longer deck joists – one at the top and one at the bottom (3cm from the top and bottom edges). These marks are where the galvanised nails will go to secure the longer joists to the shorter ones creating the frames. Make the marks align with the centre of the adjoining inner joists. This will total eight marks per frame – two in each corner of the frame.
Use a wood drill bit to drill pilot holes into the pencil-marked areas. A pilot hole provides a guide hole to help direct the nail and prevent the wood from splitting and cracking. The drill bit should be thinner than the nail's shank and drill to the same depth as the nail.
Use a claw hammer to hammer 100mm galvanised nails through the pilot holes to fix the joists together.
Repeat in every corner to create the two joist frames. Our joists are 144mm in height, so together they make a sandpit depth of 288mm.
Step 4
Lay one joist frame in position on the lawn and tap in builder's pegs halfway into the soil at the outside corners.
Lift out the frame and join the pegs with the builders' line or string to outline where the hole will be dug.
Step 5
Away from the hole, stand the two frames on their sides. Stack so that the longer joists on the top frame are on top of the shorter joists on the bottom frame (or vice versa). This creates a sturdier, more robust join - though isn't possible if the sandpit isn't completely square.
Once in position, clamp the two joist frames together with quick-release clamps. Make sure that the frames are flush and square with each other.
Repeat to secure all four sides of the joist frame, and then remove the clamps and place them flat on the grass.
Step 6
Create the horizontal seating around the top of the sandpit using deck boards.
Measure and mark a 45-degree angle a couple of centimetres in from one end of a deck board using a rafter square. The longest edge will form the outside of the seat around the sandpit (as illustrated). By bringing the measurement in slightly from the end of the board, you'll create a nice pointed tip when the board is cut, producing a better finish when the seat boards are fitted together.
Step 7
Clamp the deck board to a workbench and cut along the marked line with a panel saw (as shown) or use a mitre or circular saw if preferred.
Step 8
Lay one deck board in position on top of the joist frame so the shortest length is flush with the inside of the joist frame. Position the angled end with an inside corner of the joist frame.
On the other end of the board, mark the point where the inside of the board meets the corner of the frame. From this point, measure and mark another 45-degree angle (in the opposite direction to the previous cut). Place it back in the workbench cut the new mark and then reposition it back on the frame.
Step 9
Repeat Steps 6 and 7 and make another angled cut on a new board.
Lay this second board in place on the joist frame so that its angled end butts up against the first board.
Mark, measure and cut the other end and repeat until all four boards are in place with both ends angled.
Step 10
Lay the seating frame upside down on a solid, flat surface (for example on a patio or piece of plywood - not straight onto grass).
Glue the joints of the deck boards together with a waterproof wood adhesive. If required place some cardboard underneath to protect the surface from any glue drips.
Lay a perforated metal plate on the underside of each corner of the deckboard frame. We recommend attaching to the grooved (or more grooved) side of the deck board as this will be the underside of the seat, leaving the smoother finish on top.
Hammer six 20mm galvanised nails into the metal panel positioning three on each side of the board. Wipe away excess glue with a damp cloth and leave to dry.
Step 11
Once the glue has dried, flip the frame over and sit the deck board frame in place on top of the joist frame so the metal panels are on the underside.
Use a wood drill bit to drill pilot holes into the top of the board frame every 30cm around its inside edge, directly into the centre of the joist frame.
Remove the drill bit and replace it with a countersink bit – this should be the depth of the screw’s head. Drill into the pilot holes to create countersunk holes. Countersinking sets the screws to a consistent depth without splitting or denting the wood. It also ensures the screws will be flush with the surface of the timber for a tidier finish.
Remove the countersink bit and screw in 75mm deck screws. For a smooth and neat finish, fill the holes with wood filler and sand smooth.
The frame is now completed.
Step 12
Treat the timber to protect it from the elements and leave it to dry.
Step 13
When the paint is dry, place the frame onto a sheet of weed-control fabric or pond liner.
Lap the fabric/liner up to the outside of the frame, just below the seat and trim to fit with a utility knife or heavy-duty scissors.
Secure the fabric/liner to the frame with 12mm clout nails hammered in every 10cm around the frame.
If the liner isn’t wide enough, overlap the lengths by 30cm. There's no need to glue it together, just overlap and tack in place.
Step 14
Add a thin layer of sand - 10 to 15mm into the bottom of the hole. This helps cushion and level the area, while also aiding drainage.
Lower the finished box into the hole with the assistance of a helper.
Step 15
If using a pond or plastic liner - perforate it with a garden fork to create plenty of drainage holes.
This isn’t necessary with weed control fabric as this is porous, allowing rainwater to drain away as well as preventing weed growth.
Step 16
Fill the pit with play sand. Fill to no more than 10cm from the top so there’s room to dig and build castles.
Once you have decided whether to build a wooden sandpit, why not take a look at what we have to offer, call us today on 0121 706 0404 or email sales@johnsonstimber.co.uk.