Porcelain slabs not taken

27 Jun 2009
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United Kingdom
Had a builder lay a load of bradstone 600 x 600 porcelain slabs September last year. They used bradstone slurry primer on the back of every slab as suggested in order to have them stick to the sand/cement base.

The builder wanted to leave the resin pointed until this time of year. The problem is that most of the slabs have loosened. Is this due to weather and water or a problem with the slurry primer etc.

What would you suggest should be done now? I’m guessing it’s pointless putting in the resin now as it’ll not work due to the loose slabs?

Thanks for any help you can give me on this tricky one.

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Have them all relaid and pointed up as soon as the base has set.

Seems like water has got into the voids, frozen and expanded, breaking the adhesion.
I had a horrible feeling that was going to be case. Gutting in an understatement hey. So they will lift fine I guess it’ll just need a breaker to remove the old base and then a new base, new slurry and as soon as laid it needs the pointing doing?

I know it depends on size for how long it’ll take but you think it’s a big job yeah or not really? Just one of those things hey?
If they are loose, then wont they just come up easily? You can grind the cement off the back and prep the base and re-lay. If some are still stuck down then they should be able to be left in place.

You'll just need to watch the surface levels if fitting slabs in between slabs - chop the base out a bit more to allow for this.
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I’ve got you. If a high percentage are loose (which to be honest it looks like that the case) then they could really do with all coming up and relaying. This’ll help with the levels too as you said.

As you said, the cement should come off the backs pretty easily. It looks like porcelain doesn’t have much suction at all.

Do you think I need to use the bradstone slurry primer again? E.g. buy more (it’s expensive) or is there just as good slurry mix that can be mixed up by the builder?

Just want to get it right this time so it’s reay for the summer and won’t need redoing again :(
The primer is important as it helps the slabs stick to the mortar bed as they are not very absorbant. You may be able to use a different primer product, but as this is mainly cement, you could potentially use normal cement and an additive such as SBR - which is a resin, like PVA glue. But you need to research this for yourself. I tend to mix cement and SBR and fine sand for a similar use for external concrete repairs and leveling, but you need to check things out for your self to see if that would be suitable for this use on those slabs.

Don't forget that you will need a new bedding layer of damp mortar too

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