Movement in new sandstone patio

[Kalozo]

Hi,

Please can I get some advice about a new patio I have just had fitted by a landscaper. The patio is a quality branded sandstone 900x600 slabs.

The old patio was dug out and new MOT laid and whacked. The slabs were then laid on a mix of sharp sand and cement.

Now about 2-3 weeks there appears to be movement in a large number of the slabs:

1) Some slabs obviously move if you stand on them corner to corner

2) A large number of slabs sound hollow when you stand on them. If you stamp on them they seem to shake

3) There are a hairline cracks around the geofix on many slabs

The landscaper has said that the ones that are moving corner to corner definitely need to be lifted and laid again but is less concerned about the others.

My view is that any that sound hollow, shake or have hairline cracks also need to come up. Please can I get some views?

Also, what might have caused this? If it all has to come up and be re-laid (70m2) I want to make sure it doesn’t happen again.

Many thanks….

 

[r896neo]

Rocking flags plain and simple are caused by low skill level on the part of the paver. Sometimes it is more prevalent with drier mixes of bedding mortar as they are harder to bed correctly but again its not the fault of the mix its purely poor workmanship.

Using a wet mix reduces the difficulty because the mortar will spread under the flag better as its tapped down.

Any flags with a perceivable movement need to be re-laid.

Hollow sounding flags are usually a bad sign but not always.

Hairline cracks usually indicate slight movement.

In my opinion you should lift 3 or 4 individual flags from random different areas of the patio and check the bedding. If they have been spot bedded it should all be relaid ideally.

It depends what was quoted, if he quoted a full mortar bed then he'll have to suck it up and re-do. If however he didnt specifically say how they would be bedded its less clear and you may struggle to get him to re-do it for free.

As a side note geo-fix is crap and if you do relay use something else. MArshalls 365, easyjoint and gtfk vdw are all slightly dearer but much better.

Flags should be fully bedded leaving no hollows under the flag. Below is before bedding and then how the bedding should look after the flag is tapped into it.

After bedding