Leaking balcony over garage problem

[motco]

I have a flat roof over part of my garage and it doubles as a balcony. It is laid on concrete structural beams forming the garage roof and comprises flagstones grouted/pointed with mortar so it is stable. It was relaid about seven years ago but no rubber or other membrane was installed between the beams and the flagstones but two layers Cromarpol waterproofing coating was used instead - builder recommended it.

Needless to say the roof lets water through into my garage to an increasing extent. I recently had a local bloke come and re-grout the flags because the grouting was loose. Water still gets though presumably when it pools on the grout lines. I don't even mind the water in the garage as such because a wet car drips on the floor, but it takes alkaline salts through with it and damages paintwork.

What I need is a clear coating to the entire balcony surface if possible across flagstones and joints alike. I don't mind if it alters the surface finish of the flags as they are nothing special. It will have to be resistant to occasional foot-traffic in warmer weather though. Does anyone know of a coating that can be applied over existing flagstones? I realise that a membrane ought to have been laid but that is now impractical for a number of reasons - cost being one. Any coating should last a few years before needing re-application. Thanks in advance chaps!

 

[foxhole]

https://www.promain.co.uk/rubber-anti-slip-rubber-paint.html

 

[motco]

Thank you, foxhole, for your prompt reply. I shall note that suggestion as it does look from the website as if it would sort the leak. I would, however, prefer a clear coating if possible. I'm not bothered if it darkens the surface or makes it glossy, but a solid colour might look a bit 'industrial'. If all else fails then I'd use it! The alkaline drips etch the paintwork of cars in the garage and putting a cover on each time is tiresome. Thanks again.

 

[conny]

How about some kind of latex ceiling sealer in the garage? A sort of rubber membrane that you could apply with a roller and give a nice thick finish?

Not sure if such a thing exists but could be worth looking in to.
Maybe the stuff foxhole referred to but on the ceiling instead of the balcony.