The Brew Cabin

I have laid some Bradstone Old Town Flags on 10/1 bed.

3 days later when I went back to grout some of the flags were rocking slightly.

When I laid the flags Should i have loosened the the top layer with trowel after screeding.

Will Grouting with 4/1 dry mix pervent rocking

Best regards.

Did you simply prepare a screeded bed (not recommended for this type of flag) and then plonk down the flags without consolidating them?

I recommend the individual bedding method for these flags, as a screeded bed cannot accommodate the variations in thickness, but even with a screeded bed, the flags need to be consolidated by tapping "to refusal" with a pavior's maul, as described on the main website.

Pointing flags that are already rocking will hold them firm in the short term, but, after a week or two, they'll start to move again. It's essential that the flags are firm and stable before pointing.

I prepared the screeded bed and tapped the life out of them. I then checked for rocking by pressing on diagonal corners. all seemed ok on the day.

the variations in thickness was not a problem the level seems good .

Is there any way of fixing them solid now??

What are the joints like - did you butter them when laying or are they still empty?

Also, how many flags are affected?

they are empty.

about 10 flags affected in 50mSq

the day after i laid them there was some foot trafic, would this have caused them to loosen.

I am not trying to make excuses But i would like to know where i went wrong so that it does not happen again.

Thank you very much for your help and patience.

You might be able to 'tighten up' the 10 loose flags by making a very, very wet mortar slurry, 3:1 mix of BUILDING sand with cement, a dash of plasticiser, and mixed to the consistency of Tomato soup. Mix it in a bucket and keep stirring to prevent it settling.

Very, very carefully pour it into the joints around the loose flags, and then straddle the flags and cause them to rock, so that they draw in the slurry to fill any minor voids. If you spill or splash any of the slurry on the surface of the flags, wash off immediately with clean water.

The slurry should set in 24 hours or so and hold the flags tight. The idea of using building sand, rather than the usual grit sand, is that it consists of finer grains and so offers enhanced workability as a slurry and can rget to the parts other sands can't reach.

Once they've been treated with the slurry, don't let anyone walk on them for at least 24 hours, preferably 48-72 hours, if poss.

As to where you went wrong, the most frequent cause is incomplete consolidation. It's not always easy to spot that a flag is moving ever so slightly when laid, so it's worth checking each flag two or three times. The second biggest culprit is allowing the edges of the flags to be trafficked too soon. If you have to walk across the newly paved surface, try to ensure your foot falls only on the centre of the larger flags, and not on the edges or on the smaller (300x300mm) units.

As luck would have it, if the joints are buttered when laid, this can help keep the flags firm while the bedding hardens off, but, if you think this could be a problem likely to recur, consider using a moist mix, rather than semi-dry, for the bedding. This uses a minimal amount of added water, just enough to bind everything together, and can sometimes be a bit more forgiving of partial consolidation than a semi-dry mix.