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Posted: Mon Apr 06, 2020 5:29 pm
by Major Tom
Thanks for the FAQs! I had read the loose flags one but not the laying over one.
What’s a little different in my situation, is that I’m laying all of my flags (not just the odd one), and I’m re-laying them all in the same position on the same bed.
They were only laid ~5 years ago and the bed looks pristine. No cracks, dead flat.
Pic: [img]https://i.ibb.co/PcssZjL....mg]
It’s a little too low and could do with being raised 15-20mm.
What worries me is that when I laid it the first time, I (attempted to) follow the guides on this excellent site to the letter, bedded on a 10:1 moist mix. But, the flags didn’t stick, so I should try something different this time. No point repeating the same mistake.
So, I wondered what works best for sawn Indian sandstone.
My leading options currently are:
1. Try bonding them To the existing bed with a slurry.
2. Try a flexible tile adhesive
3. Lay on a (another) bed of sharp sand - stronger mix? Wet mix? Or try builders sand since I don’t need structural strength, just good adhesion?
5. Combination of slurry and new bed
Posted: Tue Apr 07, 2020 10:56 am
by Tony McC
If you can get a bed of 15-20mm, then a 6:1 mortar, with plasticiser, wet mix (S3 - https://www.pavingexpert.com/conc_slump#site-terms ) and use a bond bridge slurry primer both on the existing bed and on the underside of the re-laid flags.
Anything less than 15mm would be best done with an outdoor grade tile adhesive as it's damned hard, near impossible, to mix a thin-set mortar from off-the-shelf materials. You need specific fine, angular sands, very high quality cements, and special plasticisers/strengtheners/bonding agents - easier to buy a ready-mixed product.
Posted: Wed Apr 08, 2020 5:28 pm
by Major Tom
Thanks a lot for your help, much appreciated.
I think I’ll go with a 15-20mm mortar bed with bond bridges. I’ll report back when done.
Posted: Thu Apr 09, 2020 9:58 am
by Tony McC
Please do - and post/send photies, as the OP did. It's very useful for future readers.....
Posted: Sat May 30, 2020 11:42 pm
by Ray Ray
I am curious how these fixes have stood up a few months later?
Posted: Sat May 30, 2020 11:47 pm
by Ray Ray
Would love to know how these methods are holding a few months later, similar problems unfortunately.
Posted: Sun May 31, 2020 9:07 am
by Ray Ray
Any updates on how these all have survived?
Posted: Thu Jun 18, 2020 7:01 pm
by Major Tom
I’ve only just finished mine!
In the end I laid them on a 20mm bed of building sand, 4/5:1 mix. Could have used sharp but there were shallower areas and building sand was a bit more forgiving. Used a screed on the bed, small area at a time.
I sealed the tiles before starting, and it was easy to wipe away any spills.
I applied SBR slurry to the tiles only, no stains.
It’s tons better than it was, feels really solid. Time will tell how it holds up but I can’t see it going anywhere.
Just wished I’d borrowed a cement mixer. Took a while mixing 1.5t with a paddle mixer!
https://imgur.com/gBmPRAs
https://imgur.com/5gQ5Nne
https://imgur.com/Whnf0Kr
Finished - Used easyjoint (mushroom):
https://imgur.com/s0x50Hz
And before... (definitely pays to look after it!)
https://imgur.com/itf6WA8
In case anyone’s wondering, floorseal black spot remover worked magic on the manky tiles. And floorseal “Indian Sandstone Sealer & Colour Intensifier� seems to work well and looks natural too.
Posted: Fri Jun 26, 2020 9:31 am
by Leeg
I'm still happy to report no problems. So much so that after leaving them for many months we took the plunge on re-jointing. They will be finished today, and looking good.
Posted: Fri Nov 13, 2020 4:54 pm
by Bomber45
I came across this forum over the summer as I was having problems with a sandstone patio. The patio was laid around 4 years ago on a full sand and cement bed, jointed with geofix. The patio is under some large trees in the bottom corner of our garden and as a result was always pretty wet and dirty and from the beginning the geofix was awful. Fast forward to this year and I decided to break out the what remained of the jointing compound and start again, but unfortunately during the process of breaking it out, several slabs became loose. The bed itself was very good, flat and solid, and so I wondered whether I could simply stick them down with an adhesive of some kind, and after a bit of Googling I found this thread. In the end, I decided to go with an SBR slurry. I made sure the bed was entirely clean of debris, and then applied the SBR mix to the underside of the flag with a notched trowel. When setting them, I was careful to ensure that I put them down in the same orientation as they came up - the flags had a machined underside but nevertheless any minor imperfection in the bed or the flag would have potentially led to rocking issues. I was very careful not to get any of the mix on the surface of flags to avoid any staining and the whole process went very well. A few months on and I have not had any issues.
Posted: Fri Nov 13, 2020 5:07 pm
by Bomber45
Posted: Sun Nov 15, 2020 10:07 am
by Tony McC
Good testament, Bomber!
As I've just said in a completely unrelated thread, I think you had luck on your side, especially given you were attemmpting to re-fix calibrated (what you refer to as 'machined' flags) which can be very tricky. I have a tranche of emails from folk that have tried to re-fix using SBR and had no end of problems, mainly, I suspect, due to not getting the origional bed spotlessly clean before re-seating the flags.
Enjoy your success! 
Posted: Thu Nov 26, 2020 5:33 pm
by Bomber45
Thanks Tony. Yes, I was very careful to make sure the bed was clean - any small amount of debris would have been enough to make the flags rock. Fingers crossed they stay in place!!
Posted: Fri May 28, 2021 1:45 pm
by DROSS
I have 65 metre square of Indian stone which needs rejointing. The original jointing was called something like Rompox, but it soon went grey (from white), became friable and has now virtually disappeared. What’s the best alternative for replacing at this stage? Need to keep the stone clean by pressure washing or a chemical cleaner, so the jointing needs to stand up to some method of cleaning. Flags are well bedded, so no problem there. Any thoughts?
Re: Re-jointing and loose flags
Posted: Tue Jun 08, 2021 10:59 am
by Tony McC
That must have been the Rompox 1 part product, the Rompox Easy. For a 1-part jointing compound, it's actually one of the better ones, but it's still not in the same league as the 2-part compounds, including Rompox D1 or Rompox Drain (the permeable one).
Others worth considering should include the VDW 850+ which you can see here -
https://www.pavingexpert.com/point_ncc01