A step by step GUIDE

Please note:

Ensure you are wearing appropriate safety protection throughout your task. Wet mortar can burn exposed skin therefore it's essential you are wearing suitable protective gloves and long sleeves to protect your arms.

Ensure you read our advice before beginning work on your new design project which will allow you to be fully prepared with everything on hand, ready to complete your perfect garden.

Be advised this is a simple guide to building a garden wall. We highly recommend consulting with a Bradstone Assured member for a professional installation.

Tools you need

All walls, whatever the height, need to be built on a firm foundation. This might be an existing concrete base, or for a 'dwarf' wall (a wall less than 600mm high), on top of an existing paved area.

Tools you will need:

  • A pair of trowels and a pointing bar
  • String building line
  • Long spirit level
  • Rubber mallet
  • Length of timber
  • Spade/tools for digging out
  • Club hammer and bolster chisel
  • All-in ballast, building and sharp sand is available from your stockist and they will be able to advise quantities.


Important: If you plan to build a retaining wall higher than 600mm or for any wall over 900mm, we recommend that you use an experienced professional such as our Bradstone Assured Landscapers.

STEP 1 Digging out the foundation


Mark out the line and position of the wall and then dig out for the foundations.

For dwarf walls, the foundation will need to be 150mm thick and wide enough for the walling blocks and an additional 100mm spread either side. The finished foundation should be at least 50mm below ground level.

STEP 2 Laying the foundation


Lay level concrete foundations using six parts all­ in ballast to one part cement.

Mix the ballast and cement and then add water. You will need a fairly wet and pourable concrete so that it flows into the trench footing and is easy to level out.

Simply pour the concrete into the trench, spread it out, and then tamp down with a length of timber to expel any air pockets that might have formed. This creates a rough and rugged finish that will be an ideal base for the mortar.

Then use a long spirit level to ensure the concrete is flat with no slope or fall in any direction.

Ensure you leave the concrete over night to give it chance to harden before you move to step 3.

STEP 3 Setting the string level


Start by dry laying the first course of blocks out to check where they will sit on the footing and whether you will need to cut any blocks to fit.

Then move the blocks out of the way and set up a taut string line. This acts as a guide to both the alignment and level of the first course of walling blocks.

Set the height so that it is level with the top of the blocks and make sure you use a spirit level to check it is flat with no fall or slope.

STEP 4 Preparing the mortar


For wall building you need a brick laying mortar of three to one mix. That's three parts building sand to one part cement.

Mix together with a little plasticizer to make the mix more workable. Add just enough water to make a smooth and pliable mortar that is easy to spread.

It needs to be stiff enough to support the weight of the walling block, but soft enough to allow you to work with it and settle the blocks onto it.

STEP 5 Building the first course


First make the mortar bed. Place a line of mortar onto the concrete footing and ripple it with the point of the trowel to make sure there is enough 'give' when you set the block onto it.

Put enough mortar on the footing for the block you are laying with a little extra to ensure the end of the block is fully supported.

Place the block into position and using the rubber mallet gently tap the block down to the correct height set by the string line.

Although the string line should be a good guide, double check your levels using the spirit level. Then it's on to the next block.

The mortar should slightly exude from between the joints, and any surplus should be cut off with the trowel.

Remember to fill the vertical joints by applying mortar to one end of the block before positioning it adjacent to the previously laid block.

Keep checking your levels - you can never do this too often!

STEP 6 Building the wall


Stagger the blocks on the next course to ensure the vertical joints don't coincide.

Where there are gaps of less than a block's width, you will need to cut a block. We recommend you use a club hammer and a sharp bolster chisel.

Ensure you have marked the block carefully before you cut it.

STEP 7 Pointing the joints


Use a pointing trowel to smooth off the mortar that has been squeezed out, as well as filling the gaps.

STEP 8 Adding coping stones


If you're adding coping stones to the top of the wall, then plan the joints you need to avoid vertical joints coinciding, allowing a 10mm joint gap between each coping stone.

If you're using flat coping stones, ensure there is an overhang both along the long face and the short end.

Then lay following the same steps as the walling blocks.

Three tips for success

As a reminder, follow our three tips for success:

  • Make sure the foundations are level and solid
  • Check your levels frequently with your spirit level
  • Never build more than six courses at a time