Recommended dimensions and construction for a raised garden bed

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Raised beds can be made from almost anything that will hold soil.The best and some of the cheapest materials are discussed here.

Also on this page

Correct dimensions and safe construction.
The ideal height of a raised bed made for you.
Formula to work out the width to make the beds comfortable, safe and easy to use.
How to make a raised bed

If you are elderly or a disability makes bending and stretching difficult, raising your garden beds can make growing fruit, vegetables and flowers a whole lot easier.

In this article we will look at materials, measurements and constructing your own raised beds.

Using safe materials and getting the height and width right are important and I will explain how to calculate the dimensions for safe and easy to use raised garden beds.

Constructing raised beds can be reasonably cheap, without sacrificing safety and practicality.

They can be made from almost anything that will hold soil and won't rot. Railway sleepers, used tyres, old wooden planks even old plastic buckets and straw bales

How to work out the best height, length and width for raised garden beds.

Recommended height for raised beds

The height of a raised bed will be determined by what’s best for you. Think about the position you will garden from, standing, kneeling or sitting next to, or on the edge of the bed. Check that the measurements work for you before building or having the raised bed built for you.

How to work out the best height, best length and best width for you.

Working out the ideal Height: Stand, kneel or sit if working from a seated position or using a wheelchair, hold a trowel in the hand you work with and reach out with your arm slightly lower than your shoulder. Measure the most comfortable position from the lowest point of the trowel to the ground and that's the best height for your raised bed.

If working from a wheelchair or wheeled garden seat the height of you raised garden bed is calculated when seated in the wheelchair with the chair in a side on position.

The recommended width of a raised bed, which you can access from both sides, can be up to 1,000mm wide. At this width you should be able to reach all areas of the bed with ease.

If you are only going to access the bed from one side, the maximum width is around 500mm.

Working out the ideal width: hold the trowel and without stretching, reach across the imaginary raised bed and work the trowel as if planting or weeding, that's the best width for your raised bed.

If working from a wheelchair or wheeled garden seat the width is measured when seated in the wheelchair with the chair in a side on position.

The length: the length of your raised garden bed can be as long as you can safely make it and navigate. A sleeper bed formed with the sleepers laid flat, forms a useful seat to sit and work from and to take a rest. The length of the bed will then be determined by the space you have available and how big you want the bed to be.

What can be used to make raised garden beds.

Raised beds can be made from just about any material that will hold soil. some of the cheapest materials are in fact, the best.

Top tip. It's a good ideal if you are making your raised bed from sleepers, tyres or concrete blocks, to plan to have the top wide enough to form a seat to sit on as you are working on the bed.

Used bricks and breeze blocks are cheap or even free. Breeze blocks laid on there side make a good seat to garden from.

Sawn timber is a fairly low cost material for making raised garden beds.

Old planks nailed or screwed around a simple frame of corner stakes that have been well hammered in is cheap and very simple to make.

Any container that's stable and deep enough to allow space for roots to spread. Potatoes grow and do particularly well in old plastic buckets.

Old pre formed garden ponds are a cheap way to make a raised garden beds. Make sure the liner is set stable on blocks or bricks to get the desired height and drill or hammer a few holes in the bottom for drainage before adding a layer of gravel and the top soil.

Old tyres can be used to too, two or three car or lorry tyres stacked on top of each other make really cheap raised beds to grow your vegetables in.
Rubber tyres are particularly good for growing in as they absorb the heat in the morning and radiate it off at night, this helps to keep the plants warm and encourage growth.
For stability and safety the tyre stack should be held in place with stakes hammered in around the inside.

Hay or straw bales are interesting and well worth a try. I have included some hay bail garden tips on this page hay bale garden

Concrete slabs set on end in the ground, not pretty but If you know anyone who is pulling up an old patio the slabs could be free.

Upturned lawn turf. If you know anyone turning a lawn into a patio or stripping a lawn, ask them for the turf they are removing, they will be pleased to drop it round for you, saves them hiring a skip.

Sleepers look good and are fairly easy to make safe and if fixed on there side, form a seat to work from or rest.

How many sleepers to make a basic raised bed.
Four to form a six foot square about a foot high, would cost £100. Eight to form a two foot high x six foot square raised bed would cost £200 and so on.

Basic instructions about how to construct a sleeper bed further down this page.

Softwood boards. To make a relatively cheap, rustic looking raised bed, you could use pressure-treated softwood boards fixed horizontally onto stakes driven into the ground.

Boards are cheap and won’t need a great deal of skill or strength to construct and can be stained to look attractive and fit with your garden. A bed made from softwood boards is not particularly strong, so the maximum height of the bed should be around 450mm.

Construction tips are further down this page.

Purchasing ready made raised bed kits.

You may prefer D.I.Y. using self assembly raised garden beds, they usually come complete with stakes and screws and instructions on how to assemble the kit. I have featured a couple here.

Building raised garden beds

Whether you choose to build the bed yourself, or employ a professional, will depend on your skill and budget. Beds using stone or brick might be best left to experts unless you have hard landscaping experience.

Safety is extremely important – the bed must be capable of containing and bearing the weight of the soil.

Whatever material you choose to construct your raised garden bed the completed bed should be comfortable and practical to work on when gardening.

The beds must be safe to use, If you are building it yourself, using concrete or stone, or the height is over 2ft, consider these points.

The higher the structure the higher the chance of failure. It is important to be aware that as the highs of the retaining wall increases, the force trying to topple it increases by a large factor. For example, if you double the height of the raised bed, the tipping force can increase by a factor of three or four times.
Frozen soil expands as it freezes and can seriously damage the material retaining the soil. So in areas where frost is likely this can be minimised by backfilling the wall with gravel. The soil and area itself needs to be well drained so that water can't build up behind the wall.
If it's not possible to drain the water away from the wall or raised bed structure, water can be drained through the walls of the raised bed by installing weep holes in the base
Garden Drainage information can be found on my garden drainage page
Building retaining walls information can be found here dry stone walls

How to construct a bed using boards.

Use 25mm x 150mm pressure treated softwood board, cut to the lengths required.
Place 1,000mm x 50mm x 50mm stakes at corners and at every 1m length.
Drive the stakes into the ground, to leave 450mm above ground. Check the stakes are straight and all in the ground to the same height.

Set the lowest boards 50mm below ground level and fix the boards to the stakes with galvanised nails or screws. Butt the next row of boards up to the first and screw or nail on. Repeat until all the boards are fitted.

How to construct a raised bed using sleepers.
A bed made from railway sleepers is strong, long lasting and looks natural.
Sleepers come in a standard size of 250mm × 200mm × 2,400mm and work best laid horizontally. They can be layed on their edge or flat forming seating.

Sleeper are very heavy to handle and fixing requires a certain level of skill, strength and drilling. If you are using reclaimed railway sleepers the tar can be toxic to some plants and can stain clothes and hands. A better option is to use new oak sleepers. Most timber merchants stock them.

Construction tips.
• Mark out your bed area.
• Cut the sleepers to length and cut the ends to overlap at corners.
• Sink the bottom sleepers into the ground to half their depth.
• Drill holes in the sleepers at 1m centers, 25mm wide by 75mm deep.
• Tap 150mm long dowels into the holes. • Fix the next layer of sleepers by locking dowels into matching holes.

Drill and fix the next layer of sleepers.

• At the corners and 1m intervals drive 1,000mm × 75mm × 75mm stakes into the ground inside your bed, burying half their length.
• Attach each sleeper to the support stakes using 200mm coach bolts.
• Finish by Laying hardcore or 20mm gravel for drainage and then fill with soil.

How much top soil will I need to fill a raised bed?

About one ton of top soil will fill a 6ft x 3ft x 12" bed.
Find a local supplier who will deliver and possibly tip it into the beds for you.
You can advertise on freecycle for topsoil and stuff to form a raised bed but you will probably need transport to collect it. Or if you want it delivered in a bulk bag the organic stuff featured below is very good and good value.

What soil is best for raised beds.

Any soil from your garden will do, sandy soil will need compost added. Loam is ideal, clay is hard to work,but is actually very good stuff to grow in,its full of nutrients the diggings the problem.

Digging in lots of grit sand makes it easier to dig. Read this if you want to improve clay soil. Also remember, deep digging can be a thing of the past, as long as you keep it weed free and fork it over now and again,tips here

no dig gardening

Improving and keeping raised bed soil in top condition.

When you hoe, rake or fork the soil over add some grit sand and home made garden compost until the texture is how you want it. You might want to consider no dig gardening I have explained how to start here gardening without digging

You won't need to lay weed suppressant fabric, weeds will struggle to grow though a foot of soil. Most weeds are airborne, so will grow on top of the weed suppressant fabric anyway.

If you have a bad back or a disability that stops you bending or getting down low or garden from a wheelchair, building wheelchair accessible raised garden beds, makes it a lot easier to keep on gardening.

More about garden layout for disabled,elderly and wheelchair gardening, disabled garden layout

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I design and build accessible gardens, incorporating raised garden beds, for elderly gardeners and people who find bending or stretching difficult. Tips and contact details can be found hear Garden design for elderly.