Sloped gardens can be difficult to use and enjoy, but with a little planning and effort you can create tiers which can be both practical and look great. There are various ways to shape a sloped garden but this article will cover a two tiered garden.
The levels will be created in the easiest way possible using a wooden sleeper retaining wall. This method can be used for tiers of up to 1m height. Taller tiers will need steel posts.
Keep a look out for our articles on alternative tiered designs for both more gentle and steeper slopes.
Before starting its worth noting that this method can be labour intensive and will require multiple days to complete, just make sure you are up to the task before hand.
This guide will cover the practical aspects of creating tiers but there are other design aspects which should be weighed up too.
How to make a sloped garden into a two tiered garden
Tools
- Spirit level
- String line
- Measuring tape
- Laser level
- Trenching spade
- Post hole diggers
- Hose or watering can
- Staple gun
- Tamping square
- Saw
- Impact driver
Materials
- Skip
- 100x100mm wooden fence posts
- Pond liner
- Hex bolts
- Post mix (1 per post)
- 100 x 200mm treated sleepers
- Staples
Step 1: Work out the drop
In this step you need to balance what you want with what is practically possible and affordable. Most people want one large area, but this can difficult and expensive to achieve.
Think about where the sun hits the garden and what you would like on each level.
Perhaps you want a seating area on the upper level and a vegetable patch on the lower level. Or a BBQ shelter on the upper level with a seating area and a pond on the lower.
Start by measuring the length and height of the slope from top to bottom using a level, stick and measuring tape. If you want to go pro the use a laser level.
The height of the upper tier will depend largely on what is surrounding it, you wont be able to elevate or lower the ground too significantly. Choose a level which would mean not too much added or lowered on the other areas of the slope.
This is where the compromise comes in as you may be limited to placing the retaining wall in only a set few locations.
Step 2: Dig out the area
Dig out the area up to where you want the retaining wall to go. This will best done with an excavator and you should take care to follow best practices before carrying out any excavation.
Its common to hit rocky clay soil when digging down to any depth, it can be extremely hard to dig through with a normal spade so we recommend using a trenching spade.
Think about what you want to put in this area, if you are planning on having paving there you will want to dig down to at least 150mm below the desired level. Check out our how to guide on laying paving for more information.
Dig back to 300mm behind where you want the front of the retaining wall to be. This will leave room for the posts and sleepers.
If you are digging up to a fence, wall or other barrier make sure not to dig too close to it or undermine it or it could collapse. Leave earth with no more than a 45 degree slope running up to the edges.
The final stages will show you how to hide these edges
How much waste will there be?
There is a common problem when disposing of waste, how much will there be and how do I get rid of it?
Simply work out the volume of the area removed in cubic meters then multiply this by 1.8 to get it in tone.
A 6 yard builders skip can hold around 8 tonnes.
Step 3: Install wooden posts
The retaining wall will be supported by 100 x 100mm fence posts which sit 600mm in the ground and finish 100mm below where you want the top of the retaining wall. Make sure they are pressure treated so they won’t rot.
To guarantee adequate strength the posts should be place no more that 1.2m apart with posts 100mm away from each end.
Using the trenching spade and some post hole diggers, 200x200mm holes for each post to slot into. Place each post into the hole, pour in the recommended amount of water and ensure it is straight and in line.
Its a good idea to do the end posts first, set up a string line between the two then set the rest of the posts from this string line. You can see how to do this in our slatted fencing post.
Step 4: Install the retaining sleepers
Using 150mm hex bolts securely fasten the sleepers to the fence posts in an overlapping staggered pattern. In our example we have gone up to 0.8m height which would be 4 sleepers in total.
Its likely you will need steps installed, these can be built into the retaining wall but the number 1 priority is to ensure the strength of the retaining wall. You may find it easier to build the steps afterwards.
Water flows down hill and can seep through retaining walls if not protected, using the pond liner will protect the surface of your retaining wall from erosion and water seepage.
The pond liner is a heavy duty, reinforced rubber sheet that will mean water won’t be able to come through it.
Using the staple gun, attach the pond liner to the back of the sleepers leaving a 50mm gap at the top to hide it from visibility.
Step 5: Level the upper tier
Wait at least 24 hours before starting this stage to ensure the post mix has had adequate time to set. Using a spade fill in the area behind the retaining wall.
Backfill and tamp down with a tamping square.
Use a spade and a spirit level to excavate the area of the slope which is too high, disposing of any turf or poor quality soil. Use any remaining good quality soil to fill in the lower areas.
Check your levels from time to time to save yourself repeat work.
You will have noticed that you risk exposing the foundations of the fence or walls surrounding the upper tier. The next stage deals with this.
Step 6: Install the borders
To hide the sloped edges left to support the border fence you will need to install some type of decorative border.
We have opted to keep with the style and turn this into a raised sleeper bed which will look great and maintain the integrity of the fence.
Its a good idea to fit the sleeper borders in place the tamp down the soil to give the fencing as much support as possible. Top the bed with 100mm of top soil and then get your favourite plants in there to complete the look.
Step 7: Pave the lower area
With the borders in place, the retaining wall completed and the soil topped up you just need to lay some paving slabs down. We used a natural Indian sandstone tile that fits in perfectly with the existing patio.
To conclude, you have seen a broad overview of how to turn a sloped garden into tiers. This two step method is great for giving you the maximum usable space.
Just remember with tiers this high its essential to set up some sort of barrier to prevent accidents, especially if you have small children at home. One way to do this is with a post and wire fence, or you can also buy some pool safety rails that are designed to fit around pools.
We will be releasing new articles on different varieties of sloped lawn over the next few weeks, so stay tuned for more great tips.
