I've laid some Marshalls Chancery paving slabs(Honeydew colour) on 10:1 sharp sand mix and buttering using 4:1 building sand and ordinary cement.
I pointed a small test area a few days ago using a 4:1 mix of silver sand and white cement (with plasticiser) because I want a light coloured pointing.
The pointing itself looks good but a mark has appeared around the edge of each slab about an inch in. It seems to be a brown stain similar to the way this paving goes brown when it rains.
Is this normal and will it go away or am I doing something wrong. I plan to finish the pointing this weekend as I'm going on holidays for a few weeks.
Any advice gratefully appreciated.
Urgent - pointing sample discolouring the slabs! - And i need to finish it this weekend
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NovicePaver
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- Joined: Thu Apr 28, 2005 12:48 pm
- Location: West London
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NovicePaver
- Posts: 14
- Joined: Thu Apr 28, 2005 12:48 pm
- Location: West London
I've spoken to Marshalls technical help and they said that basically the problem was caused by me not pointing the joints as soon as they were laid.
I laid the slabs over a couple of weeks and wanted to point them all together at the end partly due to the fact that we couldn't decide what colour to point them.
They say that the 15 mm gap acts as a reservoir when it rains and that the water would have soaked into the edge of the slabs.
I'm kind of confused by this as the mark wasn't evident until after I pointed them.
He also said that over a period of time, with weathering and curing the mark will reduce or possibly disappear.
He did also say that I should have laid them on a bed of mortar as per the Marshalls instructions .
Let this be a lesson to anybody else planning to lay such slabs to point them within a day.
I laid the slabs over a couple of weeks and wanted to point them all together at the end partly due to the fact that we couldn't decide what colour to point them.
They say that the 15 mm gap acts as a reservoir when it rains and that the water would have soaked into the edge of the slabs.
I'm kind of confused by this as the mark wasn't evident until after I pointed them.
He also said that over a period of time, with weathering and curing the mark will reduce or possibly disappear.
He did also say that I should have laid them on a bed of mortar as per the Marshalls instructions .
Let this be a lesson to anybody else planning to lay such slabs to point them within a day.
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Tony McC
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That's bollocks: in fact, it's double bollocks.
Firstly, the fact that the joints were left open for a period is totally immaterial - did the rain water land only on the joints and none of the surface? Did you notice any water hanging in the joints?
The phenomenon you decribe is known in the trade as 'picture framing' and it can occur with any wet-cast flags, whether they are pointed immediately, left a few weeks, or even if they are dry jointed. The reason behind its appearance is complicated, but it's partly a curing phenomenon, so blaming it on the way you laid the flags is Marshalls' way of deflecting any responsibility from themselves.
The second bollocks is that laying them on on a mortar bed would have prevented this happening. It wouldn't, and, in fact, there is a lot of evidence from contractors that laying on a full mortar bed (wet mix) actually excerbates the problem. This, we think, results from the fact that there is a lot more "free" cement available to produce the phenomenon and that the high water content of a wet mix helps carry that 'free' cement into the body of the flags.
Marshalls laying advice - that would be the same Marshalls that advocate spot bedding, wouldn't it? Nuff said!
Firstly, the fact that the joints were left open for a period is totally immaterial - did the rain water land only on the joints and none of the surface? Did you notice any water hanging in the joints?
The phenomenon you decribe is known in the trade as 'picture framing' and it can occur with any wet-cast flags, whether they are pointed immediately, left a few weeks, or even if they are dry jointed. The reason behind its appearance is complicated, but it's partly a curing phenomenon, so blaming it on the way you laid the flags is Marshalls' way of deflecting any responsibility from themselves.
The second bollocks is that laying them on on a mortar bed would have prevented this happening. It wouldn't, and, in fact, there is a lot of evidence from contractors that laying on a full mortar bed (wet mix) actually excerbates the problem. This, we think, results from the fact that there is a lot more "free" cement available to produce the phenomenon and that the high water content of a wet mix helps carry that 'free' cement into the body of the flags.
Marshalls laying advice - that would be the same Marshalls that advocate spot bedding, wouldn't it? Nuff said!
Site Agent - Pavingexpert
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NovicePaver
- Posts: 14
- Joined: Thu Apr 28, 2005 12:48 pm
- Location: West London
Thanks for your reply Tony. I kind of guessed that Marshalls were just covering their own backside.
Anyway the good news is that I didn't point the remainder of the slabs until the end of a very dry week in the hope that any moisture in the space between the slabs would dry out.
This seems to have done the trick as there is virtually no discolouration of these slabs. As the area I pointed first will be covered by a shed it doesn't bother me but I thought it may be useful information for anybody else who has a similar problem.
Anyway the good news is that I didn't point the remainder of the slabs until the end of a very dry week in the hope that any moisture in the space between the slabs would dry out.
This seems to have done the trick as there is virtually no discolouration of these slabs. As the area I pointed first will be covered by a shed it doesn't bother me but I thought it may be useful information for anybody else who has a similar problem.