How to build a raised bed
- Sleepers are heavy so use a local supplier to minimise transport costs
- This is a job that definitely needs a friend to help you
- Plants in raised beds need watering more frequently than at ground level
- If you have long handled tools you’ll need to invest in shorter handles
- Remember you can only make square or rectangular beds with sleepers
How long will it take: Give yourself at least a couple of weekends
Approximate cost: Sleepers cost from £20 each
Wear metal toe-capped boots to prevent a trip to A&E, and work with a friend – those railway sleepers are not light! It’s important to ensure that your raised bed is capable of bearing the weight of the soil. If you’re in any doubt, call in a professional.
Step 1: decide on your site
A sunny or partially shaded spot will work best and try, if possible, to locate it near your garden tap as raised beds get thirsty. Make sure the pathway to your raised bed is well-drained and not slippery.
Remember, as sleepers are wide, you’ll have to reach that much farther into the bed to maintain it – something to bear in mind if you suffer with a bad back. If you can access the bed from both sides you can comfortably go up to 1m width but if it’s single-side access we’d say no more than 500mm. Height wise, make your bed no more than two sleepers high if laying them on their narrow side, and three high if laying on their widest side.
Step 2: mark out and prepare the bed area
With string and pegs, mark out the area where your bed will sit, making sure that your corners are exactly at right angles. Dig out the soil where the sleepers are going to be placed and fill with 25mm of building sand. The bottom sleeper should be sunk half it’s depth into the ground. The sand helps with levelling and also helps prevent the sleepers rotting.
Step 3: cut the sleepers
Now cut the sleepers to the correct length. If you’re not feeling terribly confident, have them professionally cut. Otherwise, you’ll have to do it the hard way with a handsaw… Not easy work, so buy a new hard point saw to help as much as possible.
WARNING: Never use a chainsaw unless you are properly qualified.
Step 4: position the sleepers
Sink the first sleeper into the ground to half its depth. Now drill 25mm holes into the top of the sleepers at 1m centres and 75mm deep. Now tap 150mm long dowels into the holes.
Step 4: repeat the next layer
Fix the next layer of sleepers by fitting dowels into matching holes which you will have drilled in the underside of the next layer of sleepers. If you are adding a third layer of sleepers, offset your dowel holes from the first set.
Step 5: fix the support stakes
Now, at the corners, and 1m intervals along the sleepers, drive support stakes measuring 1m x 75mm x 75mm into the ground inside your bed so they touch the sleeper sides, burying the stake as deep as possible, and then cutting it off level with the top of the sleepers. Drive 100mm coach bolts through each stake into each sleeper.
Step 6: line with polythene
This is an important step, particularly if you’re planting vegetables. Some of the preservatives used to treat railway sleepers can be toxic and can leach into the soil, so lining with polythene will keep your soil clean. Then lay hardcore, a permeable membrane, and then your topsoil.