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The Best Patio Mortar Mix for Laying Paving Slabs: [Simple Guide]

In this guide, we’ll help you find the perfect patio mortar mix ratio and let you know the tools you’ll need.

Creating your own mortar mix for patio slabs is easily done once you know how, but you’re going to need to do some mathematics! Not only that, but there are a few tools you should keep to hand to make sure your concrete mix is perfect for slab adhesion.

We’ve spent plenty of time over the years mixing mortar, and while it’s easy enough to get the mix for patio slabs ready-made, you may wish to go the DIY route.

Whether you’re a professional wanting to make sure your patio slab mix is perfect, or if it’s your first time mixing up bedding mortar, we’re here to help.

Keep reading and find out:

  • The golden ratio for mortar mix
  • The tools you’re going to need
  • Whether it’s worth using a cement mixer or not
  • How to create pointing for patio slabs
  • Whether or not ready mix patio mortar is worth the money

Ready to lay a patio or bed a paving slab? Here’s what you’ll need to know about the mortar mix.

Making the Perfect Mix

Tools you’ll need

Grab the following patio paving tools required to get started:

  • A solid, reliable spade
  • A good shovel
  • Suitable protective gloves
  • A bucket full of water
  • A thick plastic sheet (the larger, the better)
  • A wheelbarrow

And, for the mix:

  • Sharp sand (under 5mm aggregates)
  • Cement

You’ve got the dry mix and your tools – so let’s get going.

  1. First, put on your gloves, lay out your plastic sheet close to the mortar site, and fill up your wheelbarrow with the sand.
  2. You’re then going to need to lay four parts of sharp sand onto the sheet – ideally with your shovel. The 1:4 ratio with cement tends to cover all bases.
  3. So, be sure to add the one part cement, again, to your sheet, with your shovel. Mix it all in and create a ‘hill’ or ‘lump’ with a slight hole in the top.
  4. You’re going to want to pour your water into the hole – pint by pint should do it, mixing as you go. Keep mixing – and as you’re already wearing suitable protective gloves, grab handfuls to check the consistency.
  5. The consistency checks are pretty simple. It’s too dry if the mix crumbles through your hands. There’s too much water if it’s a damp consistency and squelches out – it’s overly wet. Take your time!

Once you’ve mixed your mortar to a consistent colour and thickness, it’s ready to apply to the ground. Remember, it’s best not to do this in bad weather – even if you wait a few minutes for the rain to stop. Let things dry out before you start the whole process.

When it comes to actually laying the paving or relaying a few loose flags, you’ll need extra tools such as a spirit level and a rubber mallet, so head back to the toolbox.

This short video shows how to mix a small amount of mortar.

The Patio Mortar Ratio

The best mix for pointing patios is ideal at a ratio of 1:4 – one part concrete and four parts sharp sand. In some cases, you can use 1:3, but that’s only really going to help when you’re pointing.

Trust us – this ratio’s been used for decades. Anything other than 1:3 and 1:4 simply won’t set – and that’s defeating the object!

Using a Cement Mixer

You should use a cement mixer is ideal for more extensive paving areas – you’re going to need a lot of foundation mix before you start laying. For whole driveways and bigger patios, hand mixing can be a struggle.

Cement mixers allow you to make enough mortar easier – yes, you’re still going to need to follow the ratio, but it’s quicker to mix.

You can hire them pretty affordably per job. If you’re going to use it for a while, then rental costs sharp add up. Take a look at the best cement mixer to buy on this list if it’s a big job.

Where you can hire a cement mixer

  • HSS
  • Hirestation
  • Speedy Services
  • Jewson
  • National Tool Hire Shops

What’s the Maximum Mortar Bed Thickness for Paving Slabs?

Expert advice on wet mortar will vary, but your full mortar bed should ideally be at a thickness of around 30mm to 40mm. This will make sure that your flag settles at 10mm high (maximum). Any thicker, and you’re going to be piling your entire area high, conflicting with your damp proof course.

Using Mortar Mix for Patio Pointing

You can sometimes use the same mix for your patio pointing. This is probably worth doing if you have excess mortar to use. However, you’ll need a very steady hand, as it’s precise work.

  1. If using mortar mix, 1:3 cement to sharp sand is ideal. You’ll need a pointing trowel, too.
  2. Gently trowel and press wet mortar into the joints, smoothing along with your pointing bar.
  3. Be careful not to stain any other slabs with surplus mortar. It’s a pain to clean off!
  4. Leave to harden for a few hours, and sweep once done.

If you do get some on the slabs, then this guide explains how to get rid of mortar on natural stone.

Alternatively, you could use a jointing compound such as Geofix, which will remove the worry of staining. It tends to be more expensive but useful.

You can also use a dry sand mix and set with water too. The choice really is yours here – providing you have a good solid foundation of mortar, you can point slabs your way.

What about Ready Mix Mortar?

If you’re worried about getting sand and cement mix right, you can always buy a ready dry mix. This simply needs water for mortar preparation, following half of the steps to the mixing up above.

Great brands for ready mix mortar include Blue Circle, Bostik, Resincoat, Hanson, Sika and Marshalls. You can pick it up reasonably cheaply from Amazon, TradePoint, B&Q and Screwfix. £8-£10 for a 20kg bag of Blue Circle, for example, seems to be a good deal.

There’s nothing inherently wrong with using a ready mix for preparing a foundation base. However, some of us prefer the tried-and-tested DIY route!

FAQ’s

Can you lay patio slabs on soil?

No. For a finished patio to ‘stay put, you need a firm foundation in a solid sub base. Always follow mortar preparation – lay a patio on soil, and it’s going to wobble and sink.

Can you lay slabs without cement?

You can technically lay a patio with just sand, but using a cement mix is widely tried and tested. We wouldn’t recommend you use sand alone unless you want to experiment.

What is the mix for patio grouting?

It’s generally recommended that you use a ratio of 1:3 cement and sand for grouting and pointing. Again, you can also buy ready mix grout if you’re unsure. This guide explains the best way to point a patio, step by step.

Should I use sharp sand or builders sand?

Sharp sand is coarser than basic builders sand, and it’s best for mixing with concrete, slowly adding water throughout. You’d generally use builders sand to bulk up, to point, or for plastering and bricklaying.

The Last Word

Getting that concrete mix right for your paving slab project is easier than you might think, but it still takes some practice. You don’t just need enough paving slabs and appropriate safety protection to get started – before you start laying directly, you need to follow the golden ratio of 1:4.

When applied at minimum depth, the right consistency will help to support your slabs for years to come. A wet mix should be easy to make by hand for smaller tasks, but for bigger patios and paving demands, consider getting a bag of ready-mix and hiring a cement mixer for ease. Before you lay the paving slabs, make sure you know which route you’re taking.

There’s nothing wrong with buying paving mix if it helps to make a simple job. It’s just a case of getting it wet enough, applying it to the ground and carefully laying the slabs. Leaving joints (naturally) to the end, you can even use the same mix to point.

Yes – you could also call in the professionals – but mixing paving mortar is easier than it looks. Be sure to follow the above to get started.