How to Build Flagstone Steps in Your Garden

Summary: How to use natural stone or flagstones as steps in your garden and how to prepare the ground before building your flagstone steps. Build a garden feature with beautiful natural stone.

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Natural stone is a very attractive, if rustic, material to use for steps in the garden. It won’t suit all situations, but stone is perfect for a decorative winding path with steps, or a secondary set of steps to access a different area of the garden.

Flagstones can be incredibly heavy so make sure you have enough help on-hand to lift them safely, or use a patch-work of smaller stones.

Preparation

Because stone sizes can vary a lot, it is best to source your stone before you start to prepare the ground for the steps. If you are using one large stone per step, keep in mind that the stone needs to be large enough for the step above to overlap, so each step is stabilised by the one below. If you are using smaller stones you will need to set them into a bed of mortar.

See our project on building garden steps for information on how to work out how many steps you need, and step sizes. You will also be able to refer to the diagram below for a visual guide on how to lay the steps.

Once you have your stone, plan your steps by laying out the stones and work out roughly how much you need to dig out for each step. Use string lines to mark out the steps, and dig out the rough shape of the steps. Whether you are using large or small stones for your steps, you may want to lay a concrete foundation for the first step, to ensure a secure footing.

Mark out the position of your first step, and dig a trench about 200mm (8”) wide and 150mm (6”) deep around the front and sides of the area. Lay about 100mm (4”) of hardcore in the trench, compacting it with a club-hammer, then mix up and add a layer of concrete up to the top of the trench. For help with the concrete see our Mixing Concrete project. Allow the concrete to dry for a couple of days before continuing.

Building the Steps

If you are using large flags with one per step, the weight of the stone itself will hold them in place – you just need to ensure each step has a firm footing so that it doesn’t sink into the ground. To achieve this, it’s a good idea to lay each stone on a layer of well-compacted hardcore or scalpings

How to lay flagstone steps in the garden

How to lay flagstone steps in the garden

Lay your first step on the concrete foundation, and mark out the second step – it should overlap the first one by at least a quarter of the overall depth of the stone. Dig out the step area to around 100mm (4”), then fill the space with hard-core, compacting it down with a club-hammer. Add a layer of sharp-sand or mortar on top of the hardcore to ensure a level base, then lay your second stone. Repeat this for each step.

If you are using smaller stones, you will definately need to mortar them into place to ensure they are secure and don’t move. Dig out the space inside your concrete foundation and fill it with hardcore, compact it well, then add a layer of mortar over the foundation and hardcore. See our Mortar Mixes project if you need advice on mixing mortar.

Position your pieces of stone carefully, trying to make sure they are all level with each other and do not present any trip hazards. Add more mortar between the stones, using a pointing trowel to give a smooth finish.

Move on to the next step, digging out and filling with hardcore again, being careful not to disturb the mortared stones on your first step. You may wish to let the mortar harden before proceeding. Your second step should overlap the first step a little, but because you are using several smaller pieces of stone there is nothing to gain from overlapping a lot as you would with large flags. Add a layer of mortar over your hardcore base, then position and mortar in the stones as per the first step. Repeat this for each step until you’re finished.

Allow the mortar to dry for a couple of days before using the steps.

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