Leaking flagstone patio...

I have a flagstone patio on the flat roof of my garage. Recently, during rains and snow melting, water seeps through the flagstone surface (probably through cracking mortar) infiltrating down and coming through cracks in the concrete ceiling of the garage, by which time it has picked up enough mineral content that it forms stalactites of minerals on the garage ceiling. The bad part is that it drips on the car and causes stubborn mineral stains on the car's finish. How would you go about waterproofing this? I have applied a concrete/patio sealer, but it didn't help. Dig out and replace the mortar around the flagstones? Maybe hydraulic patching cenment on the garage ceiling cracks and a super-duper masonry sealer/waterproofer on the patio surface? What's the best masonry sealer out there? All suggestions welcome.
-Howard
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(muttering) ...flagstone patio on the roof of his garage... Might be good to talk to an engineer/architect type. I'd hire a professional. Tom
Someday, it'll all be over....
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Take off the stone and redo it . Leave the stone off .... Or put the stone back on pay alot and expect it to leak in 10 yrs
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snipped-for-privacy@email.com (howard) wrote:

Seems to me that if all you did was hydro patch the ceiling cracks, all you'll be doing there is make the leaking-in water find somewhere else within the interior roof structure to move to and leak out of. Or worse, maybe continually pool up and work on any cracks you don't/can't see during freeze-thaw so the concrete starts coming down in big chunks sooner or later.
Seems to me the best way to remedy it (short of trashing the patio) is to not only redo all the mortar, but put a new seal on the roof itself. Back in the day, they used to slop a thick coat of roofing tar with big mops on flat roofs, but that was back in the day. Myself, I wouldn't own anything with a flat roof on it larger than a tool shed even if someone gave it to me for free, so I have no idea about the best way to seal a flat building roof these days. A competent commercial roofing company might be a nifty place to start for advice or an estimate.
AJS
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