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Posted: Wed Jul 23, 2014 2:19 pm
by AngusB
Hi, I am laying a black limestone patio in an L shape of about 40sqm with a drain gully and recessed drain cover. I am using 600 x 900 x 22mm flags.
there is already a concrete sub base in place so the mortar will go directly onto that.
I have read a lot on here but lots of differing opinions, what are the key things I should be thinking about for...
Should I drill drainage holes in the concrete subbase
Mortar mix building sand to course sand ratio
Pointing with resin based product
anything else?
any thoughts much appreciated
thanks
Posted: Tue Aug 12, 2014 9:46 am
by 1964johnr
Just laid a black limestone patio myself. I'm not a professional and didn't realise how finicky this product is. Things I have learnt which might help you.
Try to lay stones with as little as you can in terms of mortar stains. They can prove very difficult to remove.
The pointing mix needs to be perfect to avoid staining. I used an almost dry mix of 4:1 ratio of sharp sand and cement which went down well with only minimal staining. If you get the mix to wet it will be a nightmare.
There will probably be a lot of effluescence in the first few weeks after laying. Do not seal in this period of time otherwise you will seal all the effluescence and mortar stains inside the stone.
Advice on this site is to wait at least 8 weeks after laying to seal and make sure you use an expensive, high quality sealer that is known for it's good results on black limestone. I have researched and e-mailed companies and these are the ones which seem to be used a lot by professionals. Aquamix Enrich N seal and Romex Colour seal.
Over the last few weeks the colour of my stones has faded from black to dark grey. I haven't sealed yet and am hoping the colour returms after sealing.
If you need to clean stones of mortar staines be very carefull what you use and always try out first on a spare or broken slab and leave for a couple of days to see the effect. NEVER use acid brick cleaner on black limestone, it will destroy it. I started with warm water and washing up liquid, which had minimal results. I then moved on to diluted bleach which had the same effect. I then tried neat white vinegar on a spare stone of course, which was scrubbed in to the stone with a washing up scourer and then rinsed immediately and thoroughly with the hose for a couple of minutes. The vinegar was the most succesfull, eradicating 95% of staining.
Hope some of this helps.