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Topic: Re-jointing and loose flags< Next Oldest | Next Newest >
Leeg
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Posted: 15 Sep. 2019,21:01 QUOTE

We had a large area of Indian sandstone laid a couple of years back. It was jointed with one of the resin jointing compounds. In places it's come loose as I suspect it either wasn't deep enough or was just brushed in without being compacted. The installer did admit it was the first time he'd used the system.  So I've started removing it with a view to repointing.

With the joints removed I expected the flags to be stuck rigid to the mortar bed, but they can be lifted. Around 10% will need rebedding as they were wobbly beforehand, but I would have never known there was a problem with the majority as they were rigid until the joints were removed. Will they be ok once repointed? I've lifted some and had a look and the bedding looks perfectly flat and solid its just not bonded to the flags.   Would it be wrong to lift them and add a little all weather no-nails type adhesive or something else?  I really don't want to have to rebed everything with mortar.  The flags go back in position after lifting providing no debris is in the way.  I'll vacuum the whole area if it means I can avoid rebedding!  Anyone any suggestions? TIA
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Tony McC
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Posted: 16 Sep. 2019,09:59 QUOTE

You can never rely on jointing, no matter how good, to secure loose or rocking flagstones. It rarely lasts more than a couple of years.

The notion to use No-Nails or similar is a regular suggestion from inexperienced DIYers and, sad to say, some eejits that claim to be professionals. Again, it will not last. The pressure and loading on paving are radically different to those on skirting boards or wall tiles.

The *only* effective fix is a re-lay, as detailed in the FAQ - anything else is a bodge.


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Leeg
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Posted: 16 Sep. 2019,10:37 QUOTE

Ok, Thanks.  What is the likely cause of the lack of bonding between the mortar and slabs?
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Tony McC
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Posted: 17 Sep. 2019,12:47 QUOTE

There are dozens of possible causes. Crap mortar is a common one, along with dry bedding, parched flags and dusty surfaces.

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Leeg
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Posted: 18 Sep. 2019,14:24 QUOTE

Thanks Tony.  I've no doubting that re-laying is the preferred option.  But there is no way I'm having the contractor back to break out and re-lay 120m^2 of flags and risk ruining my slightly newer tarmac drive and lawn.

There is also no doubting you knowledge and experience, and I really appreciate your advice.  But I have to look for an alternative.  My day job for the last 20+ years is designing new products.  9-5pm I'm paid to find innovative solutions to problems.  I don't always get it right, but I've a dozen or so patents to my name (I'm not bragging - its something that comes with the territory).  My boss always tells me 'if we always do what we always did, we'd always get what we always got'.  It's true that if the human race didn't look for new solutions we'd still be living in caves.  So, after looking at various options, my plan at the minute is to lift the flags one by one, vacuum the area (yes you did read that right!), outdoor PVA the underside of the flag and the top side of the bedding, leave to dry and after consulting the company involved then use this adhesive:

Power grab n bond

Then re-point with one of the resin systems but I will make sure it is tooled in and compressed.  It won't be particularly cheap (or quick!), but hopefully a lot less mess than doing it the more traditional way.  The original contractor is coming back at the end of the week to have a look at the problem.  I'll see what he offers first before I spill my beans.  If I do go-ahead I'll be sure to report back my findings.  If it doesn't work out you can tell me 'I told you so'!
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Bob_A
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Posted: 18 Sep. 2019,18:44 QUOTE

Tony
I'm sure quite a few years ago I read there was an unorthodox method (bodge) where you could remove the jointing, carefully pour a SBR slurry in, let it set and then repoint?
It was never said it would work or it was a recognised method but maybe worth a punt before lifting flags and doing it properly?
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Tony McC
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Posted: 21 Sep. 2019,12:03 QUOTE

Leg - PVA is a waste of time and money. It is water soluble and never lastd more than a few months in our near-permanently damp ground conditions in Britain and Ireland.

Which brings us to Bob's suggestion about the use of SBR or a SBR slurry, which *does* last, and is a much more effective solution BUT...  extreme care is required as even the slightest splash will stain and be impossible to shift, and it's not always possible to get the re-seated flags settled to a reasonably even level.

It *is* a bodge, but it can work on a few flags when handled correctly, which usually means someone with experience in flag handling and laying. I'd be mighty, mighty reluctant to use the technique over a larger area. :(


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Leeg
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Posted: 23 Sep. 2019,10:29 QUOTE

I must admit the PVA was the bit I had doubts about because of the water based aspect.  So I'm glad you've raised that.  I've tested a small area and its bonded really well without any primer, I just made sure it was really clean.  I'll leave them to stand without any grout for a little while before I go any further.  I reckon I need about 35 - 40 tubes to complete the job!

I know you think it's a waste of time and money, but I think it's worth a try.
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Bob_A
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Posted: 23 Sep. 2019,11:30 QUOTE

Come back and let us know please:)
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Leeg
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Posted: 23 Sep. 2019,11:40 QUOTE

Will do.
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ruler

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