We’ve written a complete guide to get the best mortar mixing ratios for sand cement mixes for whatever task you you are undertaking. In this guide we cover:
- Different types of mortar
- The difference between mortar, cement and concrete
- How to mix mortar including the correct ratios for different jobs
Some of the common reasons that you may require this guide are if you are:
- Pointing
- Laying screed
- Rendering
Although there could be many more reasons that you are working with mortar. Make sure to check out our other articles for tips on how to mix mortar or if your doing a bit of demolition, our best tools for removing mortar.
What are the Types of Mortar?
When you come to mix your mortar there are several different types that you can choose from. Here is a breakdown of each type and an explanation of what they are:
Type N Mortar Mix Ratio
It’s typically recommended for exterior and above grade walls which are going to be exposed to extreme weather or temperatures. It’s 1 part portland cement, 1 part lime and 6 pars sand as a mix, which makes a medium strength and is the best choice for general application and is the go to for most homeowners.
Type O Mortar Mix Ratio
This is a mix that is typically used for interiors or non load bearing walls as it’s relatively low strength. It’s not recommended to use this mix when working on anything external and it’s only really suitable for interior work or patching. It’s ideal for repointing or repairs and is generally easy to apply.
Type S Mortar Mix Ratio
This is a high strength mix and is suitable for many different projects and is often used for masonry foundations, sewers, retaining walls, brick patios & work that requires significant strength.
Type M Mortar Mix Ratio
This uses a large amount of Portland cement and is recommended for foundations, retaining walls, driveways. It’s quite poor when it comes to adhesion or sealing properties which makes it sometimes unsuitable for anything exposed to the elements, however it’s often the preferred mix to use for natural stone as it has a similar level of strength.
Type K Mortar Mix Ratio
It’s an extremely low strength mix that is quite soft in comparison to the others and is just primarily used for restorations such as work on historic or older buildings.
What is the difference between mortar and cement and concrete?
People often get confused as builders refer to mortar, concrete & cement differently, so it can be hard to know exactly what means what, it’s all quite confusing so to help you out, here’s a quick definition of each:
Cement – It’s a powder that is grey in colour and you can often mix it with sand which would make mortar or adding crushed rock and gravel to make concrete.
Concrete – A mix of gravel, sand, crushed rock, cement and water and is typically made extremely thick.
Mortar – Mixture of water, sand, cement but is made much thinner than concrete and is used typically for pointing or bricklaying. Making this too thick would cause cracks.
How to mix sand and cement for mortar?
Mixing mortar is pretty straight forward & easy to do by yourself, here’s a step by step guide on how:
- Get the correct sand and mortar – ensure that you use a fine grade of sharp masonry sand & for the bag of mortar use fresh unopened bags from reputable and trusted brands
- For a basic mix, measure three parts sand one part masonry cement
- Add in the water – A bag of mortar should be mixed with around 13.5 litres of water, although this can vary
- Consider adding lime – This is used to strengthen the stonework & increase the bonding, although this makes the mix dry a lot quicker
- Mortar of the perfect consistency should be able to hold on a trowel at 90 degrees but not be too thick that it’s not easy to work
What is the correct ratio of sand and cement for making mortar?
The best mortar mix depends on the task, unfortunately there’s no straight answer so here’s a few examples of a few common jobs and the best mixes to use:
| Job | Cement | Sand |
|---|---|---|
| Bricklaying | 1 | 4 |
| Chimneys | 1 | 5 |
| External rendering | 2 | 3.5 |
| Floor Screed | 1 | |
| Joints for paving | 1 | 3 |
| Pointing | 1 | 3 |
| Retaining Walls | 1 | 3 |
| Roof tiles | 1 | 3 |
Keep in mind that these obviously all require water as well, but the amount of water is as specified above, typically 13.5 litres per bag, however that can vary based on different factors so ensure you add it slowly.
How To Get The Right Mortar Ratio
There’s no one size fits all as explained above, that being said the trick above is a good way of telling if your mortar mix is fit for purpose.
Mortar of the perfect consistency should be able to hold on a trowel at 90 degrees but not be too thick that it’s not easy to work.
FAQs
What happens if the mortar is too weak?
If you’re mortar is too weak it may not bind properly, and even if it does, you will find that it will crumble away after a short period of time. It’s important that you use a mortar mix that is strong enough for the job.
What happens if the mortar is too strong?
If you’re mix is too strong then it will dry very quick, but not only that, if you manage to apply it then the chances are it will crack.
What’s the lowest temperature I can use mortar?
The lowest temperature you can lay mortar is 5 degrees, although you can add frost proofing products, they aren’t always ideal.
Sources:
https://www.buildingmaterials.co.uk/info-hub/aggregates-cement/mortar-mixing-guide
https://www.beesleyandfildes.co.uk/mortar-mix-ratios-and-cement-mixing
https://forum.buildhub.org.uk/topic/25755-training-mortar-mix
