Minimum and Maximum Mortar Bed Thicknesses for Paving Slabs

In some situations, there may be an option to increase the thickness of the mortar bed (laying course) instead of what’s recommended everywhere (which is 30-50mm) to achieve the correct finished level of the slabs.

However, the question is, is it the right thing to do or will it cause any problems further down the road to the paving?

Technically, you could go as thick as you want with the mortar bed to lay paving slabs on but the problem is it won’t be any cost and time efficient, so the maximum mortar bed thickness that is been said is 50mm, as a general rule.

So should you just get a half-ton more hardcore to make it an average 40-50mm mortar bed overall or use a bigger mortar bed to fill the lower spots?

Then what will be ideal if the sub-base is low? The simple answer and the most ideal way to think about it would be just to top up the sub-base to the right height with mot type 1 (assuming that it’s what you’ve used) because the main strength of a patio or paving that keeps it in shape is in the sub-base – belt and braces.

However, if the sub-base is low in some spots and it’s not for a driveway, you could think to get away by adding more mortar providing that there’s still a decent amount of sub-base underneath to support the slab/slabs. Definitely, it won’t be the cheapest option but doesn’t matter if you’re happy with it.

If you have decided on the mortar mix ratio to use for the bedding, you may be wrong. Yes, there’s just no fixed answer to this question so how can you decide so quickly without thinking about wholly? There is a separate page on this blog that tells why you should use this particular ratio as a DIYer (to visit there click here).

There was a post saying that they need to put an 80-100mm bedding layer in order to lay slabs in their opinion as it will be driven on which is absolutely not the best way to think about it even if it’s done considering that it’ll be liable for vehicle traffic.

If it’s for a driveway, there’s no other way around as everything is in how well you prep the sub-base. You’ll need to put more hardcore and compact with a whacker plate again to achieve the correct levels to have a thicker sub-base or else, it won’t take any longer for the problem to show up with the vehicular traffic.

There could be multiple reasons to have a thicker bedding layer. It could be because you changed your mind and now laying thinner slabs, or because of the inappropriate fall in your sub-base, or could be due to not having enough hardcore on the site.

But if you’re thinking to have a thicker bed despite having enough sub-base just to make the patio more solid then it’s truly unnecessary.

Maximum mortar bed thickness

To put it into words, the minimum mortar bed thickness is 30mm while the maximum is 50mm. Anything thicker than 50mm might be overkill and you may just waste materials and time mixing the muck.

If you’re a tradesman doing a patio for a client, increase your profit margins, it would work out cheaper to have more sub-base than sand and cement.

If you’ve read till here, you seem to be serious about your research as a DIYer. To make your work easier I recommend you to check our DIYer’s Start to Finish Patio Cheat Sheet (click here). It is a clear cut short formatted guide that will make the most sense as a first-timer laying paving.