Posted: Fri Jun 12, 2020 9:44 am
I had 2 new sandstone patios and paths laid a couple of weeks ago and I think there is an issue with the pointing. It has set hard (rock solid!), but it seems to take ages to dry out after rain (I would say that around half of it is still 'dark' 2 days after the last bit of rain fell on it - so looks like only half of it has dried out, and the rest is still holding water (at least that's why I'm assuming it's still dark). There doesn't seem to be any obvious pattern to where it stays dark and where it dries out (i.e. it's not as though one large section is dry and the rest is wet).
I used a contractor that I know quite well and also kept an eye on the process. Details about the laying:
- Laid onto existing concrete base, with a suitable fall already built in.
- Laid onto a full mortar bed (sharp sand + cement, not sure of mix)
- Each area pointed the day after laying, with a 3:1 builders sand + cement mix. This was mixed almost dry (kind of crumbly). They spent ages packing it right into the joints and finishing it off - definitely not a rushed job!
- not sealed, although an adhesive was used on the under-side of the slabs during laying.
It's worth noting that this was installed 2-3 weeks ago, so it was really hot and sunny. After pointing the first patio, they realised that the pointing may have been drying out too fast, so for the second patio they fully wetted the slabs before pointing (leaving them to dry on the surface before actually doing the pointing!). They then gave the patio a very light sprinkle of water after the pointing has been finished. I don't think that this is a reason for the issue I'm seeing though, because I'm getting the same issue on both patios.
I don't think that variations between the mixes are to blame - they did quite large mixes, and I'm seeing this variation across areas where a single mix was used.
I also don't think that it's a case of not mixing properly - the used a cement mixer and had it running for a while. Also the mix looked pretty consistent, to me at least.
Finally, I don't think that the mix drying out during pointing is to blame, because again, I can see the same problem in areas where the start of the mix was used, and where the last bits were used.
I'm wondering if this is normal or not, and what I can do about it if it's a problem. I think that it's a problem, at least visually - I would expect a consistent colour in the pointing across the patio, and for it to dry out at a consistent rate. At least I would expect it to be dry after 2 days of no rain!
I'm really stumped here - any advice would be greatly appreciated!
I've attached some pics in the link below - these were taken over 1 week after pointing, and after 2 days of no rain.
images
I used a contractor that I know quite well and also kept an eye on the process. Details about the laying:
- Laid onto existing concrete base, with a suitable fall already built in.
- Laid onto a full mortar bed (sharp sand + cement, not sure of mix)
- Each area pointed the day after laying, with a 3:1 builders sand + cement mix. This was mixed almost dry (kind of crumbly). They spent ages packing it right into the joints and finishing it off - definitely not a rushed job!
- not sealed, although an adhesive was used on the under-side of the slabs during laying.
It's worth noting that this was installed 2-3 weeks ago, so it was really hot and sunny. After pointing the first patio, they realised that the pointing may have been drying out too fast, so for the second patio they fully wetted the slabs before pointing (leaving them to dry on the surface before actually doing the pointing!). They then gave the patio a very light sprinkle of water after the pointing has been finished. I don't think that this is a reason for the issue I'm seeing though, because I'm getting the same issue on both patios.
I don't think that variations between the mixes are to blame - they did quite large mixes, and I'm seeing this variation across areas where a single mix was used.
I also don't think that it's a case of not mixing properly - the used a cement mixer and had it running for a while. Also the mix looked pretty consistent, to me at least.
Finally, I don't think that the mix drying out during pointing is to blame, because again, I can see the same problem in areas where the start of the mix was used, and where the last bits were used.
I'm wondering if this is normal or not, and what I can do about it if it's a problem. I think that it's a problem, at least visually - I would expect a consistent colour in the pointing across the patio, and for it to dry out at a consistent rate. At least I would expect it to be dry after 2 days of no rain!
I'm really stumped here - any advice would be greatly appreciated!
I've attached some pics in the link below - these were taken over 1 week after pointing, and after 2 days of no rain.
images