Extending patio - Can i keep existing sub-base

[Gin'll Fix-it]

Hi,

I have a patio newly laid that I am looking to extend. I will be lifting the existing paving slabs and then laying new slabs in the existing area and extending beyond this area. So my question is, the eisting patio has a sub-base and the mortar is intact under the lifted slabs. Can I use this as the sub-base for the new slabs in this area and then just create a sub-base with MOT1 or similar for the extended area? Or do I need to do all the sub-base the same?

Thanks for any help!

[Tony McC]

You can re-use the existing sub-base, once it's been checked for level and regulated as required, but get rid of the old mortar.

[Gin'll Fix-it]

Thanks Tony, good to hear it does not all need replacing.

Any advice on how best to get rid of the old mortar? (i.e. it is set pretty solid - break up with a club hammer or similar?). Also whilst i suspect their is reason not to lay onto the old mortar could you explain why that would be an issue?

Really appreciate the contributions on this site!!!

[Tony McC]

You can score po;ld mortar with a cut-off saw or nangle grinder to weaken it, then break it off with a hammer. WEAR A DUST MASK and, if using a cut-off saw, use dust supression.

The old mortar is an unknown quantity, so best get shut.