Laying paving stones

[yendisniaps]

I have recently laid a paving stones in a garden, bedded on about 2in sand. I filled in the gaps with dry mix, about 1 cement to 4 soft sand, then carefully watered in with a fine sprinkler. After a few days, the mortar infill has all broken up, and is now useless. I have used this method before, and had a previous failure, but also a previous success. I cant figure out what is going wrong? Maybe insufficient wetting, as the mix seems crumbly. What do you think?

 

[masona]

I cant figure out what is going wrong? Maybe insufficient wetting, ?

Yes,what happens is the cement/sand was too compact for the water to drain down to the bottom so therefore only top layer harden so the top cement break away.
See this very useful website for information.

 

[yendisniaps]

Brilliant. Thats useful. Think I will go for the dry sand infill.
Cheers

 

[Building Contractor]

Should always lay slabs on a sand cement screed, sand will eventually wash away a slabs will move..then grout them...