Laying new flags on existing sub base - Is this advisable?

[Mute]

Hi,

I have a patio which is approximately 30m2 with 600x600 concrete slabs on it.

I wish to lift these slabs and replace with mixed size Indian sandstone slabs.

The existing slabs are on a sub base of builders sand. I have been at the property for 8 years and these slabs were in since before then and they have never moved / shifted or sagged.

My question is, if I was to lift these slabs and remove 25mm off the top of the sand sub base; re-compact with a wacker; and use a 25mm bed of mortar will this be sufficient as support for the slabs or do I really need to remove 4" worth of sand and put in a MOT1 type sub base?

Like I said before, the existing sub base seems very hard and all sides would be enclosed so no sand can escape.

Any advice would be most appreciated.

Thanks

[Tony McC]

Builders' sand is NOT a sub-base. It's not even the right type of sand for paving!

Get rid and follow the advice given on the main website