Thanks for this excellent site and very useful information that it contains. I used it to plan and design the block paving of my driveway. However, I am finding myself with an unforeseen problem for which I am requiring your advice:
I have started the job and I have already completed the 12 inch-thick sub-base. I am compelled to use a 3 inch-thick layer bed instead of the recommended 1 inch bed. Do you foresee any problem in relation to that? Advice, please.
Laying bed
-
84-1093879891
You're using 3 inches (75mm) of sand for bedding? That's way too much and you will experience problems with settlement in the next few months.
Sand doesn't compact or behave quite the same as granular sub-base material when loaded - it behaves something like a fluid, and it can move, slowly and imperceptibly, but it will move.
The best solution is to top up the sub-base, adding an extra 25-40mm (1" to 1.5" ) and compacting that, before placing the bedding sand.
The figure of 50mm for bedding sand really is a maximum. You can, occasionally and on light-use projects, stretch that to 60mm, but 75mm is just asking for trouble.
Sand doesn't compact or behave quite the same as granular sub-base material when loaded - it behaves something like a fluid, and it can move, slowly and imperceptibly, but it will move.
The best solution is to top up the sub-base, adding an extra 25-40mm (1" to 1.5" ) and compacting that, before placing the bedding sand.
The figure of 50mm for bedding sand really is a maximum. You can, occasionally and on light-use projects, stretch that to 60mm, but 75mm is just asking for trouble.