The Brew Cabin

Posted: **Sun Sep 15, 2019 9:01 pm**

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

Posted: **Mon Sep 16, 2019 9:59 am**

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.

Posted: **Mon Sep 16, 2019 10:37 am**

Ok, Thanks. What is the likely cause of the lack of bonding between the mortar and slabs?

Posted: **Tue Sep 17, 2019 12:47 pm**

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

Posted: **Wed Sep 18, 2019 2:24 pm**

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'!

Posted: **Wed Sep 18, 2019 6:44 pm**

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?

Posted: **Sat Sep 21, 2019 12:03 pm**

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.

Posted: **Mon Sep 23, 2019 10:29 am**

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.

Posted: **Mon Sep 23, 2019 11:30 am**

Come back and let us know please:)

Posted: **Mon Sep 23, 2019 11:40 am**

Will do.

Posted: **Fri Nov 08, 2019 2:22 pm**

Just a quick update. Nothing has moved yet, despite all the rain and bit of frost we have had. So I've taken the plunge and done about 50-60m^2 by the above method. Progress is slow due to weather and short days. No grouting yet, that might have to wait until spring. The vast majority of flags will see little or no traffic through the winter anyway. I'm really impressed with the adhesive. I had to upgrade my sealant gun to a heavy duty item as its so thick. You also only really get one shot at positioning the flags. You get the option to wiggle it sideways into position slightly, but its practically impossible to lift the flag once you've had any weight on it, even before its set.

Posted: **Fri Nov 08, 2019 7:11 pm**

I'd be keen to see any photies of the work in action, so I could use them to show others, in the future, how to fix their own loose flags.

Posted: **Sun Nov 10, 2019 9:18 pm**

No problem, please bear with me though. As I said progress, is slow at the minute.

Posted: **Mon Nov 11, 2019 9:22 am**

No rush....in your own time is fine

Posted: **Sun Dec 01, 2019 6:28 pm**

I've managed to get some done this weekend, so hopefully the pics will work. This is why I started this task. I thought it was going to be a case of removing the existing jointing material and replace:

So, I take the loose flags up, which makes getting the joints out very easy! That's the only benefit of all this.

Vacuum both the underside of the flag and the base. This is the second brush end I've gone through and this one needs replacing.

I'll then run my bare hand over the flag and base to ensure I've not missed anything. Next, apply the adhesive:

Lay the flag back down and wiggle into place. I ensure they go back down in the same position and orientation as they came up. It's fairly easy to see when its back right as you have a mirror image from the bedding:

I then stand on it, gradually working my way around from one side to the other. The adhesive says it can cope with damp surfaces, but I try to avoid it. Which means its slow progress at this time of year. But I've probably got approx. 70m^2 held down with this method. Nothing has been re-jointed yet and probably won't be until the spring. Other than I don't really want to re-joint in the bad weather/temperatures, I figure the adhesive will also get a harsher test. If it's all still stable in the spring I will go for it then.

The Brew Cabin

Re-jointing and loose flags