Raised garden beds are extremely popular for growing vegetables and flowers. When designed and built well, they can look brilliant and become a real feature of your backyard.
Here’s how to build a fantastic planter-box style raised bed that you can adjust in size and height to meet your needs. The design even includes an optional seat for when you want to take a break and enjoy the garden.
Decide on the location for the bed. For vegetables or flowers it will need to be a sunny spot with good wind protection. Our position is beside an elevated deck area.
The techniques used to construct this bed mean that you will not require engineering-grade footings. The main posts only need to be deep enough in the ground to provide stability during construction and to stop any settling. You could build this project on a hard, level surface such as a courtyard without needing to sink footings.
Set-out for the post locations and dig post holes to around 300mm deep. Measure and cut a 75mm sleeper for the centre post, concreting it in place. As ours was against an elevated deck we used a sleeper offcut as a temporary spacer to get positioning correct. Cut and position the two end posts and concrete them in place.
The posts in this project are internal (concealed) behind the boards on the external face. If your bed is to have a split height like ours and the upper and lower beds are to be of equal size, then the centre post will need to be offset from centre biasing towards the high end to allow 50mm for fitting the centre end-boards on the outside edge. All end posts will also need to be offset 50mm towards the centre to allow for end-boards.
Tip: Using a long level and clamps makes it easier to get the correct alignment and height.
Once the three front posts are in place, add runs of uncut sleeper face-boards. Remember to check level of each before securing to posts with construction screws.
Tip: Using a drop-saw is the fastest and easiest way to ensure accurate cuts.
Using the three secured posts as a guide to measure out for the opposite posts. Cut, position and concrete in the remaining three posts for the opposite face. Cut a 1000mm sleeper length for an end board, put in place aligned with lowest face board. Check level, screw in place to both posts and use this as a height guide for face boards on the opposite side. Repeat the assembly process used for the first face, cut and add face-boards to elevated section then add all end-boards on one end only.
Using a tape and level, mark a line around the inside of each bed section approximately 350mm down from the top edge. Measure along the marked lines and cut support rails from sleepers to fit. Fix in place with construction screws. You’ll also need to add small blocks as rails to the internal posts.
The distance from side to side on top of the rails should be 1000mm (less at posts). Cut the sleeper lengths to fit as base-plates for bed. You may need to trim or rip a sleeper down to fit the last space. Position the base plates and screw to rails leaving a gap of 3- 5mm between each plate for drainage. When the first section is finished, add the end-boards as bed dividers between the high and low section before repeating the base plate process for the upper section. Once done add last external end boards.
Cut drainage fabric to size as a bed liner. Make it large enough to lap up all sides and cover the sleeper joints before stapling it in place. Fill the bed with soil, add irrigation if desired and you’re ready to start planting your new garden bed.
Tip: Add a professional finish to the bed by using a hand-plane or shaper to bevel the sleeper edges.
This is an optional addition, but a simple bench seat fitted to your raised garden bed will make gardening easier and give you a spot to relax.
On the bed face, mark the position for a seat supporting rail. The top of the rail should be around 350mm above ground level. Cut a 800mm length of 45 x 90mm treated pine as a support rail.
Counter-sink and pre-drill at least three holes along its length. Apply construction adhesive to rear. Position the rail against the line and check it is level before screwing in place with 100mm construction screws.
Cut two pieces of sleeper to 980mm long. For a seat 300mm deep cut or rip one piece length-ways to reduce to 100mm wide. Lay pieces flat and clamp together ensuring ends are flush. Cut two pieces of 45 x 90 pine approximately 270mm long for cleat plates, then add a 45-degree bevel to one end of each piece. Counter-sink and pre-drill at least three holes in each, apply construction adhesive to top (long side), position with square edge flush with back edge and sides of clamped sleepers. Fix in place with construction screws.
Apply a bead of construction adhesive to the top of the rail on the wall and then position the seat panel. Pre-drill through the back of the seat panel into the rail or skew-drill into face sleepers of garden bed and then fix in place with 100mm construction screws.
Cut lengths of decking for the side and front faces of the seat. You can butt or mitre-join these. Apply construction adhesive to the rear of the pieces and then nail or screw them in place. Cut decking for the top to 1040mm in length - this allows for approx 10mm overhang on each side. The front slat should also have a 10mm overhang. This may require the slat closest to the bed face to be ripped to size. Measure carefully and fit decking from rear to front. Apply construction adhesive and nail or screw decking down.
Add braces to add strength to your seat. Measure from the front of the underside to the bed face at a 90-degree angle. Cut two blocks of 90 x 45 treated pine to suit and then glue and screw in place around 50 to 100mm in from the edge on each side with construction screws.
Clean down the seat to remove any dust and dirt and then apply a coat or two of decking oil and your new bed is all done.
This project uses treated pine. Any beds where food will be grown or where you are likely to have contact with the timber should be constructed from non-CCA treated timber. Any timber in contact with soil should also be at least H4 rated.
You should plan and build your bed to standard sizes to avoid wastage and reduce cutting. For example, sleepers come in 2.4m and 3m lengths so make your bed to a full sleeper length and the width of half a sleeper.
To build a bed the same size as ours, you will need:
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