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Posted: Wed Aug 19, 2015 8:33 pm
by McQLon
Hi all,
I only seem to be able to access this forum at home and so apologies for no replies to these posts today.
Thank you for your replies, lots of different theories here and I don't think I'll ever get to the bottom of it.
To confirm, I have two patios, one laid and one about to be laid using the same slabs from the same supplier. I supplied all materials myself and the builders simply charged me for their time.
No acid cleaner was used. I was here when it was all laid.
One comment above says that the slabs look washed out. These were bought from the supplier and laid within a week or so of delivery. I have the remaining 60 sq meters stacked and ready to lay. As far as I can see, none of those have changed colour.
The colour change happened over a period of a few weeks. I went on holiday a week after they were laid and came back to this.
I agree the staining looks quite perfect but there are other slabs where a lighter staining has occurred and not all over the slabs. I will send some of these photos to Steve at London Stone to upload if he doesn't mind.
As I said, I can't blame the builders for laying it, I can't blame the supplier as I have no certainty over the cause.
Their website suggests using silver sand and white cement. I didn't know this until investigating today.
To confirm the materials I used:-
Wickes sharp sand
Wickes ballast
Wickes building sand
Mastercrete cement
I now have around 4 tonnes of sand remaining and am not sure whether to get rid of it and buy silver sand or SBR the bottom of the remaining slabs to prevent the stones drawing up sand.
I know nothing about paving but could write a book with the stuff I've found out today. If only I could tell for certain.
Will send more pictures as mentioned tomorrow.
Posted: Wed Aug 19, 2015 10:25 pm
by r896neo
Sorry to go on as you have already answered but are you certain that no cleaner was used.
Often someone (usually a labourer) has got a bit sloppy with the pointing and has thrown some acid on it to remove the evidence of their cock-up before the homeowner sees it.
Did you actually see all the pointing being done? was It jointed with a pointing gun, semi-dry trowelled in, slurry jointed?
Sorry again to ask what you've already answered its just i am a big advocate of grey sandstone because of its quality and consistancy so am following this thread with avid interest.
Posted: Wed Aug 19, 2015 10:32 pm
by McQLon
Hi, I saw the pointing being done, obviously not the whole thing but popped out from time to time to see how they were getting on. They used a pointing gun and then a stick of some description to smooth out the pointing.
As far as I could see, they wiped up with water as they went. I'm not certain that no acid was used but I was at the house when the work was taking place.
I called the builder today and he assures me nothing was used. I can only take his word for it.
As there are hollows he has said he will take up and re-lay the slabs. This includes the discoloured slabs which we will replace. I will watch everything and if it happens again I can then be certain that no cleaner was used. My main worry is that the entire patio eventually changes colour. The supplier did say that he had been to complaints before where the entire patio had changed colour and was adamant voids and drainage issues could be causing the colour change.
Completely unsure of what has happened and not sure how to lay the remaining patio.
Is there no way something could have happened during manufacture that has caused the changes once laid? Alternatively a dud pallet of slabs? I had 8 and a half pallets but 1 and a half of the pallets were delivered a week later than the first batch as they "forgot" them.
Posted: Thu Aug 20, 2015 9:01 am
by r896neo
There is no manufacture with riven stone flags. they are literally split apart mechanically from a large lump or rock then put in a crate.
I would be slightly wary if the supplier has had this happen before. perhaps the stone they are buying is not of a good enough spec? Not saying they have done anything wrong, perhaps just unlucky.
This is something steve at london stone may be able to advise on as he is clued in on the process as a supplier.
I would not lay the rest yet. Who supplied the stone?
Posted: Thu Aug 20, 2015 9:43 am
by London Stone Paving
Neo
There are lots of potential factors at stake that could have caused this. With the recent pictures posted we can see that there are more slabs affected than originally thought but also if you look back at the first batch of pictures there are lots of other slabs showing signs of early discolouration. I hate to say it but in a few weeks the whole thing could look even worse....sorry Chris 
If no treatment has been applied and the un-laid slabs are not yet showing signs of discolouration then something that has happened during installation has caused this reaction to occur.
Chris, it may be worth laying a few square metres of the unlaid slabs flat on the floor and leaving for a couple of weeks to see if any of these marking are prevalent or naturally develop.
Neo there are a whole host of other factors potentially at play here that could have caused/contributed to this issue. You should not put you off using grey sandstone because in the majority of cases it IS a reliable stone.
I can only give my experience of this but when blocks of grey sandstone are quarried there are different grades of quality. The higher quality blocks will command a premium price. But not only this, the reputable suppliers will have people placed at the quarries to select the better quality blocks. The reputable suppliers will also be well connected and experienced so they are much more likely to be able to lay their hands on the premium blocks.
The poorest quality blocks will often find their way into the local market but many of them will still find their way to export. Its these poor quality blocks that have these very strong iron deposits and as the gaffer rightly pointed out in one of his replies these blocks can and do find their way into the export market
Its also worth mentioning that there is a Kandla grey quarry that is well known for producing blocks with a very high iron content. Even though its a quarry I am aware of and its a quarry all my suppliers are aware to steer clear of, there is still a possibility that some of these blocks can find their way into your supply chain. This happens in times of shortage when suppliers are forced to buy outside normal channels. Buying stone in India is extremely challenging for the suppliers.
Going back to the main subject, if we are to assume that no cleaning products have been used then the marking has either come about naturally or as a result of a reaction with the bedding layer or a combination of both factors.
Chris, I mentioned earlier that it would be worth laying a few slabs out on the floor to see if any discolouration is present or developing. Roger mentioned in an earlier post about how the stone looked washed out. I would like to see if the stone has this washed out look prior to installation, so if you could lay some out and take some piccies that would be worthwhile to try and get to the bottom whats going on. Happy to upload them for you
Steve
Posted: Thu Aug 20, 2015 11:48 am
by McQLon
Hi all, I have big problems accessing this forum so apologies for my slow replies. I only seem to be able to access when I'm at home on my wifi.
In regards to the stones looking washed out, I think that is more down to my wife's photography than the slabs themselves. They don't look that washed out in real life. I will take some pictures of the patio tomorrow morning and also of some of the slabs we have not yet laid so that you can see them. I have some of the wooden pallets left so if there is any information relating to their origin there I will let you know. The supplier checked the pallets and said they were "good stones".
I purchased from Landscaping Supplies Direct who in turn got them from Castacrete. Obviously when buying the paving I had no knowledge that they could discolour and so didn't think twice about purchasing.
The slabs not yet laid have been stacked in our garden for around 4 weeks now and whilst I haven't checked all of them, they don't look to have changed colour. I will check more this evening or in the morning. Which makes me think it may be a reaction to the bedding. The trouble with me now buying silver sand and white cement is that I have a lot of sharp sand and building sand that I can't get rid of. I could purchase all of this stuff and the same things happen again.
Next time I buy a house I think I'll get decking instead!
Posted: Thu Aug 20, 2015 1:39 pm
by higgness
I think it will be interesting to see the pictures of the unlaid slabs.
Posted: Thu Aug 20, 2015 7:24 pm
by McQLon
I have just got home from work and checked through some of the slabs!
Some of these has changed colour too, albeit not as drastically as the ones already laid. Obviously I have a lot so can't lay them all out but will do more in the morning. Maybe the iron content is already very high as Steve says and then the mortar is adding to that?
I have taken photos and will send them to Steve to upload tomorrow morning.
I have also taken a photo of the pallet crate with details, maybe a clue in there as to where they came from and the patio today which is looking rather washed out and more colour change has taken place.
If it is the slabs themselves, what are my options?
Let's see the pictures in the morning and see what you experts think!
