I recently finished a job where we had to build raised flower beds using railway sleepers which involved building the beds on concrete and anchoring them into the ground since the property sat along the River Thames, meaning that they would be under water for a good month of the year! With pictures from this job, I thought it best to write an article on how to build your very own raised flower bed with railway sleepers since this job will cover every situation, and to be honest, it’s not the hardest of jobs to complete! No matter your circumstances, whether you will be building your sleepers on earth or concrete, I will explain exactly what you need and how to build your very own flower bed without having to pay a professional to do the work for you. Be sure to subscribe, as my next post will explain how to lay artificial turf on concrete which was also part of this job!

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What tools will I need to build a raised flower bed with sleepers?

Compared to my other ‘how to’ posts, there aren’t too many tools needed on this one and the ones that are needed are mostly inexpensive, and will certainly save you money when comparing prices of tools and materials compared to paying professional labor fees. Here are a list of the tools and materials needed.

  • Railway sleepers (these can usually be purchased in 2.4 or 1.2 meter lengths. Railway sleepers can be purchased as softwood, reclaimed and oak and starting from around £20 per railway sleeper.
  • 150mm or 200mm timber screws (usually have a 10mm head) at a cost of approximately £25 per 50 screws.
  • Wood drill bits (6mm)
  • Masonry drill bits
  • 13mm spade drill bit
  • Drill (or an SDS drill if building on existing concrete)
  • Hand saw (power tools are preferable but a hand saw will work just fine)

Step by step guide to using sleepers to build a raised flower bed

Step 1 – Cut the sleepers at the first level

The first thing you will want to do is measure the area to where you will be laying the sleepers and cut them so that you can temporarily place them together to make that perfect square or rectangle. This will make step 2 much easier to work with since they will already be pre-cut. Be sure to only cut the sleepers at the first level as it is best to lay them like brick work, so every other layer will have different size cuts. Just look at the corners of the sleepers in the images to fully understand as this will give you a much stronger raised flower bed, holding all of the sleepers together. Failure in this will result in an unsturdy flowerbed!

If you are using rustic sleepers then you will get away with using a chainsaw which will save a lot of time. If you are using modern sleepers such as softwood with straight edges then it is best to mark a straight line all the way around the sleeper to make sure that you cut is straight. A good handsaw will get through each sleeper in no more than 5 minutes.

Step 2 – Preparing the ground

Preparing the ground when laying on earth

If you are laying your sleepers straight onto earth (grass, soil etc..) then this will be much easier compared to building your new flower bed on concrete as depending on how high you are building your flowerbeds, you may not need to secure the sleepers to the ground. All you will need to do is mark the area that your new flowerbed will be and use a spade to level the ground. It is important to have a level ground so be sure to use a spirit level! Once done, place your ready cut sleepers into position and place a spirit level on top to make sure that they are level, if not then you may be able to tap them down with a rubber mallet to get them level if the ground is soft enough.

Preparing the ground on an uneven surface

If your laying your sleepers onto an uneven surface such as concrete, or if you have no room to dig the earth to make it level, then you will need to build a level bed using sand and cement. When we are up against this task, we just use a mixing tray as not much cement is usually needed. We first mix to a 5 part sharp sand to a 1 part cement and wet it just enough to make it ‘sticky’ and easy to work with, similar to brick laying, without making it too runny that it makes it impossible to hold its own strength when trying to create a depth. You can see in the picture below that we were building the raised flowerbed on a steep hill so had to build the bed at around 8 inches. Using a plastering trowel and a spirit level, get the level roughly right (it hasn’t got to be perfect at this point).

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The next thing you will want to do is put lots of screws into the bottom of the sleepers making sure to leave a good 2 inches (depending on how much concrete you have to work with) before gently placing the base of the railway sleeper into the concrete bed, in turn sinking the screws into the mix. Then, using a spirit level and rubber mallet, gently tap down on the sleeper until you are happy that its level. Using the pre-cut sleepers, continue this process until you have a perfect square or rectangle for your new flowerbed. At this point, it is best to wait until the next day to give the cement a chance to set enough before moving onto the next steps. As the cement sets, the screws will be held in place holding the railway sleepers securely.

Preparing the ground on level concrete

If you have a level concrete foundation that you will be building the raised flower bed on with railway sleepers then you should get away with just placing the sleepers down and screwing them together, since the weight of the soil should keep it in place. If how ever you are only having a low flower bed (1-3 sleepers high when laid on their side) then I would recommend screwing them into the concrete for extra stability.

The way that we do this is to place the first sleeper where you want it and use a 6mm wood drill bit to screw holes into the sleeper. When you think you are close to the base of the sleeper, switch the drill bit to a masonry bit and go straight into the concrete below whilst putting pressure on the sleeper making sure that it doesn’t move. Once you have made a start into the concrete, continue this process until you are happy with the number of holes. Then remove the sleeper and continue drilling into the concrete. If the sleepers are on their side. then they will only be 100mm thick, which means that the hole in the concrete will need to be at least 50mm deep if using 150mm timber screws or 100mm deep if using 200mm timber screws. Then, using a 13mm spade drill bit, drill this into the existing holes on the top of the sleepers, just to leave enough room to sink the screw heads allowing a flat surface for the sleepers above. Now all you need to do is place the sleeper back where you initially put it and screw the bolts into the railway sleeper and down into the wall plug in the concrete.

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Step 3 – Start building your raised flowerbed with the sleepers

Now it’s time for the easy bit! Now that you have the first layer of sleepers in place, it’s time to secure the next level of sleepers into the level below. Like before, cut all of the sleepers and place on top of the below sleepers, making sure to have a brick effect on the corners to secure all of them together, making a much more sturdy flower bed.

Most timber screws will say that they don’t need a pilot hole, but it’s still best to do this as it will make it easier when drilling a sink hole using the 13mm spade bit. All you need to do is drill a 6mm hole on the top of the sleepers no more than an inch deep and then use the spade bit to drill no more than 20mm deep, just enough to hide the 10mm screw head. Then, using a 10mm socket bit, screw the timber screw down and into the sleeper below. Repeat this process until you have the desired height of railway sleepers.

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Step 4 – Install a plastic membrane on the inside of the raised flowerbed

It’s optional to line the inside of your new flower bed with a plastic membrane, but it certainly helps to prolong the life of your railway sleepers. Once filled with soil, especially towards to lower end, the soil will stay damp for longer meaning that it will sit against your sleepers causing them to rot over time. Of course, this is a slow process, but we have removed enough raised flowerbeds to know that they don’t last forever!

Installing a plastic membrane or liner on the inside of your flower bed will protect it from the damp soil. Make sure to only do this on the sides of your railway sleepers allowing water to drain from the bottom and continue to treat your timber on a yearly basis to help expand its life, although this can only be done from the outside! It is also a good idea to treat the ends of the sleepers that you have cut as this new exposed timber will be untreated.

Step 5 – fill the flowerbed with top soil

If you have any rubble left around such as broken slabs or bricks then providing you have a deep enough flower bed, throw enough in to fill the first level of sleepers as this will help with drainage. We usually fill the bed with 60% top soil and 40% compost to help with the new plants.

To conclude…

Flower beds are easy to build when using sleepers providing that you are a hands on person and know your way around a handsaw and tape measure. They are a great addition to any garden and we lay just as many sleepers now as we did years ago, so they certainly aren’t losing popularity any time soon!

There is no need to fix the sleepers to the ground unless they are being laid on an uneven surface where a mortar bed will be needed, or the flower bed will be shallow enough that it won’t have any real weight. Assuming that your new flower bed is at least 3-4 sleepers high, then there should be enough weight (baring in mind that they will be filled with top soil) to keep them secure to the ground.

Prices vary greatly so make sure that you do your research! Oak railway sleepers will last a lot longer than softwood but come with a higher price tag of around £40 per 2.4m sleeper compared to the £20 softwood sleepers. We actually used rustic sleepers on this job (as seen in the pictures) which look old, but are actually new softwood. The only difference between the rustic sleepers and the softwood sleepers are that the rustic ones have no straight edges and still have the bark attached. With regards to price, they are they same.

I’ll be sure to take more pictures when I next build a flowerbed as I wish I could have shown the drilling process better as it’s not always easy to put words into action! But if you have any questions, or if I have missed anything then please do let me know! Remember, Hankintech is a place for all of us to come together and ask questions, we are a hub for everything gardening! Please don’t forget to subscribe!