The Brew Cabin

Posted: **Sat Apr 02, 2005 3:51 pm**

We have just laid about 16 square metres of Marshall's Chancery flags (about 75 flags in total). Bedding was a semi-dry mix, 8:1, grit sand and cement (as per the excellent advice on this site). We've just finished the job, and noticed that there are 4 or 5 flags rocking, probably due to incomplete compaction during laying (we were getting tired!).

Three questions, if anyone can help:

1) I would like to lift the loose flags and re-lay them to stop the rocking. Is it best to use a small amount of wet mortar, or the same mix as before, or something completely different.

2) The bedding has gone quite hard and dry, as we may have got the mix a bit wrong! Can someone put my mind at ease, and confirm that the rest of the flags won't start to rock. I've impressed the missues so far, but not if I've done it all wrong.

3) I can't point them until next weekend (a week away). Is there anything I should do until then, or do I just leave the joints empty (they range from 5mm to 10mm wide). Unfortunately I forgot to butter them during laying, so no doubt I've messed it all up.

Your assistance, comments and advice would be most appreciated, before "she who must be obeyed" tells me we should have got a man in!!!

Posted: **Sun Apr 03, 2005 11:33 pm**

1 - yes; or loosen/chisel the top 10mm or so of existing bed and replace it with fresh, damp mix material that will allow the flag to be re-seated and compacted down to required level.

2 - I'm not sure if you have got the mix wrong or not, but even the 10:1 mix I advocate does achieve a reasonable strength. If flags aren't rocking now, theyr'e unlikely to do so in the immediate future.

3 - No worries! Just get 'em pointed as soon as you can.

Posted: **Mon Apr 04, 2005 6:19 pm**

Tony - once again thanks for your comments, as I was getting a bit worried. One last question, then I'll try not to bother you again.

Where the flags are definitely rocking (there are only about 4 of 'em) I want to definitely lift them. However, if there is only a fraction of rock on a couple of others, would the pointing stop this, so it's best to leave them be, or should I lift any and re-bed if there is even a hint of rock.

Best Regards

Posted: **Wed Apr 06, 2005 10:39 pm**

It's never a good idea to rely on pointing to cure problems with the bedding. Yes: I know that very minor movement can be resolved by a bit of solid pointing, but it has to be a judgement call - if your opinion is that it's not worth lifting the flag, then try the pointing, but if in doubt, yank it out.

One 'trick' that can and does work, especially if joints are empty/unpointed, is to make a very wet slurry of 3:1 sand and cement with a plasticiser and pour that into the empty joint. Once it's in place, straddle the flag and deliberately cause it to rock so that it draws the fluid slurry mix into any voids in the bedding and fully seals the joint.

The only drawback to this method is that the slurry usually cures to a different finish to the rest of the pointing, but a bit of general crap and detritus will make it barely noticeable in a few months. If you are concerned about the visual difference, allow the slurry an hour or so to start to harden, then rake out the top 5-8mm and replace it with you 'standard' pointing mix.

The Brew Cabin

We should have got a man in!!! - New flags rocking a bit.