Posted: Sun Jul 23, 2017 4:43 pm
I’m after some advice on granite please, which I haven’t been able to find from my browsing, so sorry if any of this has been covered before.
My project started in April and includes a raised koi pond with filter house, upper and lower patios laid with 20mm blue grey and silver grey granite, edged with 50mm Marshalls charcoal standard block paving, divided by planted walls topped with blue granite copings, and a new shed and log cabin.
The granite was laid 8 weeks ago on a full mortar bed (premixed and delivered to site and was kept watered as slabs were laid), over 150 – 200mm deep granite MOT compacted over Terram. The MOT is deep as we get a lot of ground movement round here. We were advised that it was not necessary to apply an SBR to the back of the slabs as they were being laid onto a full damp bed. The granite was not sealed in prior to laying as we simply couldn’t cope with the volume (approx. 132 SqM).
There are 5mm joints between the pavers which have yet to be filled with Rompox D1, which I have already purchased. My hope was to seal the granite with Lithofin MN Stain Stop prior to jointing as I quickly discovered how easily granite stains (leaves, bird droppings, coffee cup rings), and I know that the residue from the Rompox could take up to 6 months to weather away, and must be totally gone before sealing. I will seal the concrete block with, probably, Resiblock Ultra Matt (unless someone can suggest something better), at a later date as colour enhancement is the desired goal, once any efflorescence has had a chance to appear and been dealt with. Having conducted my own trials with Lithofin, in which oil sat on a slab for 7 days without penetrating, I’m convinced this is the product for me! I also need something fish friendly once cured for the copings round the pond.
I have put together a 7 page PDF of plans and photos that can be downloaded from this link https://we.tl/YZ22hTeDBa (5mb) which correspond to the following 6 queries:
1. All the walls have been JUB rendered with a Nanoxil top coat. The pond is fibre glassed, the internal walls of the planters painted with two coats of bitumen and the filter house with white masonry paint – all many weeks ago. This weekend, following heavy rain, I noticed water seeping through areas of the bitumen, and the top 3 – 4 rows of blocks in the filter house are saturated and the paint discolouring and peeling off. I now realise just how porous the granite is and that water must be seeping through the copings into the concrete blocks. No DPM or other waterproofing was installed beneath the copings. Will applying Lithofin Stain Stop be sufficient to water proof the copings to prevent this continuing or do we need to remove all the copings and install a DPM (I surely hope not!)? If sealing with Lithofin is sufficient, what will happen to any retained moisture in the blocks? Lithofin lets vapour through, but will this be enough for the walls to dry out as they can’t dry through the render or fibreglass or should I wait until there are no more signs of any damp in the walls? I’ve been told by Casdron the granite needs to have 4 days of total dryness before applying Stain Stop – but what will happen if there is retained moisture in the walls? Will that rise up or will gravity pull it down? I am so worried by the damage being caused to the walls from getting wet that I have now covered over the pond and the planters to keep any more rain from getting in, but in a manner to allow air to circulate to hopefully let it dry out.
2. There are some mortar stains on the granite and block paving from installation, but nothing too drastic. However, over the last few weeks I have noticed what looks like mortar coloured staining appearing on the silver grey granite that wasn’t there after the initial installation. Is this colour from the mortar working its way up through the stone? If so, will I be able to remove this with Lithofin Builders’ Clean? How long is this process likely to continue before nothing more will leach out as clearly I can’t apply Stain Stop on top of this? If I can clean this off, will Stain Stop prevent any more coming to the surface?
3. Some of the granite (both colours) have strange swirl like marks that are mostly visible when damp or drying out. I noticed these before the slabs were laid and wondered if they were pressure jet marks, but the merchant denied this and advised that they would disappear when down. They haven’t! Has anyone got any idea what these are and if they will ever go away?
4. Even on consecutive dry days, the silver grey granite can appear damp in places. It can sometimes look totally dry during the day but damp in the evening, I presume, from moisture in the air. Is this still just the mortar drying process? It doesn’t show up on the blue grey granite. I can’t figure out if this is because it is more porous than the grey (hence absorbs air moisture) or if it is more dense (hence it takes longer to dry out) – but it is most definitely very different to the grey. Either way – at what stage will this be safe to seal with Stain Stop because even with 4 consecutive dry days this ‘dampness’ can still be visible even after two months?
5. Which leads me to this conundrum – when to seal and joint? Clearly we need to get the copings sealed ASAP now, but should we be leaving the patio granite to next year? If so, and we press on with the jointing, will any residue from the Rompox cause any staining coming through to become permanent?
6. And finally… we have some slabs that have become loose and the installers have relayed them with silicone sealant. This has worked for all but one which has come loose again. Since then, some other slabs have become a bit ‘rocky’ and even more sound hollow if tapped, but are not actually moving. Is silicone OK to use to re-lay – if not how should this best be done? Does a hollow sound indicate that a slab will lift or is it safe to leave? My concern here is that I don’t want to joint if slabs are going to start lifting as it will be difficult and costly to have to re-joint again. The installers suggested that the only reason slabs are lifting is because it hasn’t been jointed. If so, should we just re-lay the loose slabs and push on with the D1 jointing?
Sorry for so many questions in one go. Any advice is very gratefully received.
My project started in April and includes a raised koi pond with filter house, upper and lower patios laid with 20mm blue grey and silver grey granite, edged with 50mm Marshalls charcoal standard block paving, divided by planted walls topped with blue granite copings, and a new shed and log cabin.
The granite was laid 8 weeks ago on a full mortar bed (premixed and delivered to site and was kept watered as slabs were laid), over 150 – 200mm deep granite MOT compacted over Terram. The MOT is deep as we get a lot of ground movement round here. We were advised that it was not necessary to apply an SBR to the back of the slabs as they were being laid onto a full damp bed. The granite was not sealed in prior to laying as we simply couldn’t cope with the volume (approx. 132 SqM).
There are 5mm joints between the pavers which have yet to be filled with Rompox D1, which I have already purchased. My hope was to seal the granite with Lithofin MN Stain Stop prior to jointing as I quickly discovered how easily granite stains (leaves, bird droppings, coffee cup rings), and I know that the residue from the Rompox could take up to 6 months to weather away, and must be totally gone before sealing. I will seal the concrete block with, probably, Resiblock Ultra Matt (unless someone can suggest something better), at a later date as colour enhancement is the desired goal, once any efflorescence has had a chance to appear and been dealt with. Having conducted my own trials with Lithofin, in which oil sat on a slab for 7 days without penetrating, I’m convinced this is the product for me! I also need something fish friendly once cured for the copings round the pond.
I have put together a 7 page PDF of plans and photos that can be downloaded from this link https://we.tl/YZ22hTeDBa (5mb) which correspond to the following 6 queries:
1. All the walls have been JUB rendered with a Nanoxil top coat. The pond is fibre glassed, the internal walls of the planters painted with two coats of bitumen and the filter house with white masonry paint – all many weeks ago. This weekend, following heavy rain, I noticed water seeping through areas of the bitumen, and the top 3 – 4 rows of blocks in the filter house are saturated and the paint discolouring and peeling off. I now realise just how porous the granite is and that water must be seeping through the copings into the concrete blocks. No DPM or other waterproofing was installed beneath the copings. Will applying Lithofin Stain Stop be sufficient to water proof the copings to prevent this continuing or do we need to remove all the copings and install a DPM (I surely hope not!)? If sealing with Lithofin is sufficient, what will happen to any retained moisture in the blocks? Lithofin lets vapour through, but will this be enough for the walls to dry out as they can’t dry through the render or fibreglass or should I wait until there are no more signs of any damp in the walls? I’ve been told by Casdron the granite needs to have 4 days of total dryness before applying Stain Stop – but what will happen if there is retained moisture in the walls? Will that rise up or will gravity pull it down? I am so worried by the damage being caused to the walls from getting wet that I have now covered over the pond and the planters to keep any more rain from getting in, but in a manner to allow air to circulate to hopefully let it dry out.
2. There are some mortar stains on the granite and block paving from installation, but nothing too drastic. However, over the last few weeks I have noticed what looks like mortar coloured staining appearing on the silver grey granite that wasn’t there after the initial installation. Is this colour from the mortar working its way up through the stone? If so, will I be able to remove this with Lithofin Builders’ Clean? How long is this process likely to continue before nothing more will leach out as clearly I can’t apply Stain Stop on top of this? If I can clean this off, will Stain Stop prevent any more coming to the surface?
3. Some of the granite (both colours) have strange swirl like marks that are mostly visible when damp or drying out. I noticed these before the slabs were laid and wondered if they were pressure jet marks, but the merchant denied this and advised that they would disappear when down. They haven’t! Has anyone got any idea what these are and if they will ever go away?
4. Even on consecutive dry days, the silver grey granite can appear damp in places. It can sometimes look totally dry during the day but damp in the evening, I presume, from moisture in the air. Is this still just the mortar drying process? It doesn’t show up on the blue grey granite. I can’t figure out if this is because it is more porous than the grey (hence absorbs air moisture) or if it is more dense (hence it takes longer to dry out) – but it is most definitely very different to the grey. Either way – at what stage will this be safe to seal with Stain Stop because even with 4 consecutive dry days this ‘dampness’ can still be visible even after two months?
5. Which leads me to this conundrum – when to seal and joint? Clearly we need to get the copings sealed ASAP now, but should we be leaving the patio granite to next year? If so, and we press on with the jointing, will any residue from the Rompox cause any staining coming through to become permanent?
6. And finally… we have some slabs that have become loose and the installers have relayed them with silicone sealant. This has worked for all but one which has come loose again. Since then, some other slabs have become a bit ‘rocky’ and even more sound hollow if tapped, but are not actually moving. Is silicone OK to use to re-lay – if not how should this best be done? Does a hollow sound indicate that a slab will lift or is it safe to leave? My concern here is that I don’t want to joint if slabs are going to start lifting as it will be difficult and costly to have to re-joint again. The installers suggested that the only reason slabs are lifting is because it hasn’t been jointed. If so, should we just re-lay the loose slabs and push on with the D1 jointing?
Sorry for so many questions in one go. Any advice is very gratefully received.