Stains on new granite patio

[David 1234]

http://community.webshots.com/album/570816685Isbkmj

Please see above link for photos. I have just had a patio laid with Stonemarket granite. Everything was done exactly as per manufacturer's spec. 1 part white cement to 5 parts sand - mix was damp and 1 part PVA to 3 parts water on back of each slab. At first I thought these marks were just the slabs drying out, but now a week later in 18 degrees Celsius there is no change whatsoever. The slabs are apparently pre-sealed by Stonemarket. Any ideas?

[henpecked]

Was surprised to see this type of staining on planters outside £2mill houses built in L/spa. The landscaper didn't scrimp on spec, but,(strangely enough) water absorption is an inherent characteristic of this stone.
Not a solution but might shed a bit of light.

HP

[Tony McC]

There's a very linear aspect to those dark marks, which would suggest it's summat man-made rather than natural, but the quality of the photos doesn't really give enough detail to make an informed judgement, as it could be a seam of darker crystalline material running through a section of the mother block from which these flags were cut.

I'm not certain about this stone being pre-sealed. I don't recall this being mentioned by any of the Stonemarketeers during our conversations and there's no mention of it in their luscious brochure.

On first view, it does look like the archetypical moisture staining, and the more of it I see,m the more I become convinced that daubing PVA on the underside is no bloody use whatsoever. It may improve bonding but it does buggerall for moisture penetration.

Can you get a good quality hi-res image of one or two of the affected flags?

[David 1234]

1. http://entertainment.webshots.com/photo/2689404510105013965pNwwAe

2. http://image66.webshots.com/766/2/80/9/ ... Pbk_fs.jpg


Hi Tony and thank you very much for your reply. I've found out the hard way that Stonemarket granite is "sealed". I have had a previous disaster with this granite on my same patio.

You can see that (now ripped up and replaced) patio in photo number 1. The discolouration happened when rain came. Stonemarket said sorry, that some stone was sealed and some was not, and that accounts for the different colours.

So I had to have it all ripped up and re-laid (still waiting on promised money back from Stonemarket for re-laying). If you look carefully at the number 1 photo above, you can see that even the so called sealed stone that hasn't gone dark has some patches on. And that is the same problem that I'm having with this latest stone, something that I had previously put down to drying out.

If you look at number 2 photo above, you can see that some patches are spots, so again I think that this shows something man-made.

I am struggling to get a high res image on the photo sharing site but can easily email you one if pos.

Basically, do you think that the patches can be removed? They did feel and stay wet much longer than the bits that hadn't gone dark so that suggests to me damp.

By the way, Stonemarket told me that PVA is to make the slabs stick and not as a water proofer but nonethless we put it on as we are now so paranoid.
I'm so worried. This patio has been a nightmare, we are now on the second attempt and both were laid by the book.

[Tony McC]

Looking at Photie 1, I can't fathom out how sealing or not sealing would account for that distribution of damp. If it were simply a matter of sealed and unsealed flags, I'd expect to see differences between flags, but all I can see is variation within individual flags.

Photie 2 is more typical for the damp issue that's known with this stone, but for the life of me I'd swear that looks like oil spots. Obviously, I'm judging from a photie rather than the actual flag, but I'm sure I can detect a faint glistening that suggests an oil, and the circular nature of the 'spots' just reinforces that belief.

If it is an oil, I'd guess its a thin oil, summat like hydraulic or even a vegetable oil.

Anyway, whatever the cause, the impact is not what you want with new stone. Have you had any comment from Stonemarket?

Photies can be emailed to me at the usual address ... tony AT name-of-website DOT com

[David 1234]

Hi Tony

There is definitely an issue with Stonemarket and sealing flags. When the first lot went bad I went to an alternative supplier who had two pallets - but they wouldn't sell them to me as they said that Stonemarket were taking them back and replacing with sealed flags.

My guess is that there could be uneven or only partial sealing on individual flags. I've looked really carefully and they aren't any oil spots. Also the flags were OK until wet.

Stonemarket's technical man won't be there until Monday. The previous disaster ended in Stonemarket visiting me and promising to reimburse the labour. Also they supplied me with new laying materials. Still I was out of pocket but I just wanted to put an end to this - and now I've ended up with problem number 2.

Will email better photos to you. Thanks Tony.

[topgrafter2007]

had oil contamination probs years ago when i worked in flag manufacturing plant. was traced to hydraulic leak on loading shovel! but ended up affecting flags in similar way.

[David 1234]

Interesting. It could be I guess - will wait to see what Stonemarket come up with. Given what happened with the previous patio that had to be pulled up I do wonder if it is a sealing issue though. When wetting flags some went patchy and I would have thought if it were oil they would be patchy when in the pallet. Also the dark bits took ages to become touch dry whereas the light bits went dry a lot quicker.

[Rich H]

Damp patches are usually but not always more vague in appearance, and cover a larger area. Often they might appear more pronounced in the mornings than later in the day.

This is really bad luck, David, I know how long you've worked on this and recall the care you took to get the right design and materials.

I'm working through a similar issue with the same company where pale sawn sandstone has turned a largely indelible pink. We're six months into the process and they're really taking their time - we all know that ultimately they'll have to replace the stone and pay for the re-laying, but I guess the legal department will be ensuring that they do all they can to avoid it for as long as possible.

[David 1234]

Thanks Richard. It is frustrating. I know the stone which you are talking about. Two merchants wouldn't sell me it which set off alarm bells and I notice that it has since been withdrawn.

I will go all the way with this and it sounds like you will too.

I still can't imagine what has caused it but do think it has something to do with damp as the dark bits took ages to dry. Also, it is more pronounced in the morning after dew.

So assuming that it is damp, is there any cure?

[Rich H]

If it is moisture then don't worry - it's a symptom which generally disappears once the bedding course is completely cured, which can take months. Just in case it isn't though, I'd take photos every week so you can monitor progress.

[David 1234]

That gives me some hope - thanks. I am worried though as it feels dry around the edges plus the patches haven't altered in any way. Can it really take months to dry?

[Rich H]

The short answer is yes. Cement cures to a certain hardness rapidly but takes weeks for the full chemical reaction to finish, depending on the volume and strength as well as the ambient temperature and moisture conditions. The reaction is only complete - or so I understand - when all of the cement has reacted with the available water. While this process is continuing, it's not unusual to see damp patches on the paving - particularly with natural stone.

[Rich H]

PS When the Hoover Dam was built the engineer (whose name I'm just in too much of a hurry to look up this morning) calculated the pour in terms of setting time. The concrete was made and poured into 10' x 10' x 10' cubes - if the whole thing had been poured at once it would have taken over 1,000 years to cure!

[lutonlagerlout]

i went to the hoover dam a few years ago on my honeymoon,and the tour is excellent,i think the guy said that some of the concrete is still curing now
fantastic construction project,although a lot of men died for it
LLL