Sandstone patio coming loose

[Kalozo]

A month ago we had 65m2 of 600x900 Natural Paving Classicstone Camel Harvest laid. We now have a number of issues:

1) A number of slabs are loose and moving
2) A number of slabs sound hollow and vibrate
3) The Geo Fix grouting has failed - it can be brushed out with a normal yard broom, it washes out with a standard hose, it is cracked around the slabs

The patio is north facing. The contractor laid the slabs on compacted MOT and then a full bed of wet coarse sand and cement. No additives such as SBR were used. He was extremely diligent and appeared to do a good job in getting the patio level and long straight runs.
Once finished a number of slabs started to come loose and others sounded hollow and vibrated. The contractor returned and lifted and re-laid about 10 slabs.

Some of these slabs that were re-laid and others are now loose. Since the slabs were re-laid we now have cement stains on the patio.

The contractor is stating that the slabs not sticking must be an issue with the slabs. I struggle with this as they are a quality branded slab.

My concern is that the patio will deteriorate quickly with more slabs becoming loose and the Geo Fix failing. As soon as we fix one, another becomes loose.

Please can you advise what is causing the problems with the slabs becoming loose and what needs to be done to resolve the situation.

Thanks

[London Stone Paving]

Hard to say why they are coming loose, could be one of a few reasons:

-Not enough cement in the mix
-Not enough water in the mix
-Slabs only tapped down lightly, so no compression/strength in the mortar bed.
-Maybe it isnt a full mortar bed

Can you pull up a couple of slabs and take some photos of what is underneath?

Steve

[Tony McC]

You can't really claim someone who uses GeoFix is "diligent"!

Hollow sounding can *only* be caused by there being hollows in the bed. Blaming the flags for not bonding is like blaming a car for running out of petrol. It's the responsibility of the installer to ensure they do bond, and this is achieved by doing thorough research and discovering the joys of a bond bridge/slurry primer.

Steve's right: we need photies of the bedding, but I'd hazard a guess that the flags need re-bedding with a bond bridge and that GeoFix needs replacing with something that actually works.

[London Stone Paving]

^^^

[lutonlagerlout]

cement stains say it all to me
geo-fiz,cement stains,hollow==>spot bedded
not enough cement
no SBR
shame but its unlikely to improve
LLL

[Kalozo]

Thanks for all your comments and sorry about the delay. The contractor has agreed that something is not right and is lifting the patio and relaying. So now that it has been lifted here are some examples of the bed - you can just about make out the edges of where the slabs where.

It would be good to get your views before we start laying again. My initial thoughts are the key issues are:
1) There are hollows
2) It doesn't look like it was wet enough
3) Maybe not enough cement in the mix

Photos

I have asked for SBR to be used and to use Marshalls grout rather than Geofix. Any other suggestions as to what went wrong would be really helpful.

Thanks again

[lutonlagerlout]

the gear looks like it was wet enough,just not enough under each flag
you need to be aiming for 95-100% contact between flag and bed to call it fully bedded
cheers LLL