Can you lay paving slabs on sharp sand alone?
Without any doubt, modern callibrated paving which is paper-thin (20, 22mm) such as porcelain and sandstone or other natural stone slabs should definitely be laid on a wet sand and cement mortar bed for various reasons.
As a general rule, bigger slabs such which fall 450mm series or larger should be laid wet sand and cement mix rather than just the sand alone except those old school boring council slabs which are 50mm or more in thickness which should be always avoided for modern residential paving purposes. They’re very heavy to hold themselves in place even when laid just on the sharp sand.
However, some installers even tend to lay those huge 50mm thick slabs on a wet bed of sharp sand and cement just to give themselves a full satisfaction by eliminating any chance of the movement in slabs once laid.
What happens in case if laid on just the sand?
First of all it will be very difficult to get the levels right if you were to lay larger slabs on sand alone instead of block paving for example, where once you screed with the right level you won’t have to check time and time again with a level.
Talking about what’s wrong with laying slabs on just sand alone, it very personal but there will be a constant feeling that the are just kept there, and there’s nothing in particular to hold them in place.
There is also the risk of sand getting washed out and the slabs may sink or move/wobble over time making it unsafe to walk over them after some time. This may sound silly but there’s also no chance the grout will last in the joints because of the movement which will fall it apart.
Due to not having a firm bed support underneath, the slabs will sound hollow also creating the chances for cracking slabs because of not having a solid base underneath.
It’s all that will make you to re-lay the slabs again with proper methods this time which will last for years and years to come, and now the only way left is lay the slabs on wet sand and cement bed because it’s what the best practice is and this what professionals use.
There are many ways that you could use to get the job done, however, there are set industry practices which are made to follow to do the job upto proper standards.
If you’re asking this question and willing to lay the slabs on your own at the same I highly recommended to get our DIYers Start to Finish Patio Cheat Sheet here get ahead of these silly questions.
Conclusion
Now you know why it’s important to have sand and cement mortar bed underneath your slabs and even doing so there are some important things to know are as what ratio to use for sand and cement in your mortar mix, at what consistency, whether to use bond bridge or slurry primer. Below are some more resources to help you out.
Best Mortar Mix to lay Paving Slabs