Leaking balcony over garage problem

[motco]

Also posted in 'General' as I don't know what section it belongs in.

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!

Read more: https://www.diynot.com/diy/threads/leaking-balcony-over-garage-problem.551599/#ixzz6WEdtbWpe

 

[ted456]

Good luck with your balcony. At least you have concrete joists.
Good luck to any reader with a balcony esp. a projecting/cantilevered balcony.

We refuse to work with any kind of balcony unless we can strip it back down to basic supports, and rebuild from there with the correct, basic waterproofing.
The waterproofing is typically a single sheet DPM (membrane) thats flashed up all abutments - & if at all possible no penetrations of the membrane are allowed.

motco,
a golden rule is you keep water out of buildings - any water out of any building.
Now you have water inside the balcony (interstitial) - stripping and rebuilding is the only sensible and cost effective method of dealing with your problem.
Your problem is similar to a failed flat roof.

 

[motco]

Thanks ted456 I am grateful for the candid view. Redoing that which was already done should be carried out at the cost of the original contractor, but as is all too common, the company was a Will O'the Wisp with no financial substance and has since been liquidated, folded its tents and stolen away. I am sure your advice is not only sound but founded on knowledge and experience. However, I would like a remedy that does not involve the disruption and expense that stripping back to the supports would incur. At least not at the moment for all sorts of reasons. Is there a coating that can be applied to the flagstones which will render the grout lines impermeable? Ideally a clear coat and one that will be moderately durable? I really do understand that it is a sticking plaster but that's what I need at the moment. There is nothing in the construction that will come to any harm that hasn't already happened over the fifty-odd years it's been there - there are stalactites already! No timber nor any rebars, but only a thumping great RSJ pair that support the back of the house and I don't see me living long enough to see those corrode destructively! Thanks again.

 

[^woody^]

https://www.rustoleum.com/product-c...sundries/watertite-clear-waterproofing-paint/

5 year guarantee, apparently. You need to coat the slabs to, and completely fill any hairline cracks with a clear silicone or similar sealant.

 

[motco]

Thanks woody, I'll look into that.

 

[dontbelieveawordofit]

i’d tile it with large format porcelain tiles and waterproof and frostproof adhesive and grout.