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Posted: Wed May 07, 2014 6:49 pm
by XTA
After much umming and arring have decided to redo our 100m2 patio.
It's currently 600mm x 400mm x 20mm thick light grey flame cut granite flags laid in 2007.
We have completely removed all the grout between the flags.
If we now insert a screwdriver into the gaps, it only takes a tiny amount of levering pressure to free each flag. The flag then lift off clean, virtually no mortar on the underside of the flags.
Please see this image for what it looks like underneath, mortar bed (approx 50mm thick) appears to have sunk in the centre. Pretty much every one is the same as this photo.
http://postimg.org/image/ykbhahyl7/
The new flagstones will also be 600mm x 400mm x 20mm flame cut granite but it is very dark grey in colour, almost black.
So from a dimension aspect were replacing like for like.
Can I leave existing mortar base as is, fill up the sunken centre area with fresh mortar and use a thin (5mm) buttering of fresh mortar to set the new flags ?
OR should I really be removing the existing 50mm mortar base and starting again with a fresh 50mm mortar base ?
If removing the full existing mortar base is the way to go would appreciate advise on how to do it .... small pneumatic drill maybe ?
Have sourced the new granite directly from quarry in Xiamen, and it won't arrive in UK for another 5 weeks so have plenty of time to get the preparatory work done.
Of the 100m2 that will be uplifted I estimate 70m2 will be uncut full size flags........... if anyone can use them and will come and take them away they can have them.
Posted: Wed May 07, 2014 7:05 pm
by London Stone Paving
Hello
1. You will need to remove the whole mortar bed and start again
2. You will probably be able to break the mortar out with a decent pick axe or breaking bar. The trick is to get under it and lever it up. You should be able to break it out in reasonable sized chunks. You could get a small breaker but IME its not required
3. Put your slabs on Ebay. You will sell them without any probs
4. Why did you decide to source direct? Obviously you will be getting a better price but I would have though the freight on a part load would be expensive
Steve
Posted: Wed May 07, 2014 8:14 pm
by XTA
OK will go with complete removal of existing mortar.
FYI reason I asked was the contractor I have earmarked to relay them was only too happy to go with the easier option .....won't be calling him back !!
Never thought of Ebay
Direct is easy for me, girls in my Shenzhen office handle everything, they arrange transport to collect from quarry, bring back to our warehouse, sort, all docs, pay quarry in RMB, get domestic price (which is much lower than FOB), pallets ship out in one of our weekly containers = landed cost in UK under £7 per m2 
Posted: Wed May 07, 2014 9:10 pm
by lutonlagerlout
so you are replacing it after 7 years why?
steve is correct all bedding must be removed and the subbase must be filled and wacked to the falls
make sure you dont get fobbed off with crap,long way to return it back to china
LLL
Posted: Wed May 07, 2014 9:22 pm
by lutonlagerlout
so was it 2007 or 2009 it was laid?
I am a little confused,but surprised you are going for a similar product!
whoever lays it would do well to use SBR in the mix and maybe an sbr slurry bond bridge on the backs of the flags
best of luck
LLL
Posted: Wed May 07, 2014 9:32 pm
by XTA
Just dug out paperwork and it was actually laid in Feb 2007.
Fully understand re "SBR in the mix and maybe an SBR slurry bond bridge on the backs of the flags" - will do this as well ..... want a belt and braces job.
Posted: Wed May 07, 2014 9:44 pm
by lutonlagerlout
definitely go for the 850 then
cheers LLL
Posted: Thu May 08, 2014 6:56 am
by XTA
Yes I will insist 850 or Larsen GPM is used whichever who does it feels more comfortable with.
Have considered butting the sawn edges together for a very contemporary look but gut feeling is the flags are going to need to be laid perfectly flat as even a 1mm differential will stand out like a sore thumb.
For small additional cost quarry can put a 3mm 45 degree chamfer on all 4 top edges which might help mask any slight height discrepancy if butt jointed and could create an interesting aesthetic effect
Posted: Thu May 08, 2014 7:10 am
by lutonlagerlout
butt jointing?
where did that come from?
there are a limited number of concrete products that can be butt jointed
I wouldnt try it with natural stone
LLL
Posted: Thu May 08, 2014 8:06 am
by XTA
saw huge patio on a monster new build house recently where it was not grouted all be it flags were larger (900mm x 600mm I guess) and it looked really good .... then again it was brand new
Posted: Thu May 08, 2014 5:15 pm
by lutonlagerlout
problem is that water will go down the minuscule joints,freeze and then cause problems
they may have been tight joints like 7-10mm but unlikely to be butt jointed
LLL
Posted: Fri May 09, 2014 1:59 pm
by XTA
lutonlagerlout wrote:problem is that water will go down the minuscule joints,freeze and then cause problems
they may have been tight joints like 7-10mm but unlikely to be butt jointed
LLL
No I stood on it .......... they were butted up to the max ..... you could just about get a sheet of paper between then and I would like to think on a £5m+ build new house the contractors were at last half decent
Posted: Fri May 09, 2014 3:35 pm
by r896neo
I have seen it done also on bush hammered granite at the entrance to my local bm. Just tight jointed probably 1mm and filled with dried sand.
It has been down 4 years and still looks fine.
But just because it can be done doesn't at all mean it is the best way to do it.
a 5mm joint is the minimum in my opinion.
Posted: Sat May 10, 2014 10:14 am
by Tony McC
You can use a Close Joint down to, say, 1 or 2mm, but I'd avoid butt jointing because it is just so much extra work.
Close jointing gives you a little bit to play with so you can accommodate minor size variations in the flags without losing alignment but more importantly, it obviates the risk of spalling resulting from intra-flag pressure on those vulnerable arisses (fancy way of saying "less chipping")
Butt jointing, along with spot bedding and GeoFix, should be condemned to the big pile of crappy ideas we used to have. 
Posted: Sat May 10, 2014 12:55 pm
by XTA
Tony McC wrote:You can use a Close Joint down to, say, 1 or 2mm, but I'd avoid butt jointing because it is just so much extra work.
Close jointing gives you a little bit to play with so you can accommodate minor size variations in the flags without losing alignment but more importantly, it obviates the risk of spalling resulting from intra-flag pressure on those vulnerable arisses (fancy way of saying "less chipping")
Butt jointing, along with spot bedding and GeoFix, should be condemned to the big pile of crappy ideas we used to have.
hmm............ so close jointing (1 to 2mm) is a viable option.... but runs the risk of water getting between the joint ...freezing and
potentially dislodging the flags,even if a good SBR bond bridge is used.
Cant see the point trying to fill a 1-2mm gap with anything (sand ?) as it wont last 5 minutes with wind rain and pressure washing etc.