Should grout be somewhat waterproof?

[ScottyC]

Hi guys,

We've recently paid a company to waterproof an tile our 11x2m balcony. Having some issues with cracked tiles around the posts for the handrail but i'm also concerned that water continues to pour out from between the membrane and screed at the front edge of the balcony for at least 24 hours after rain. The back edge of the balcony, against the house does not normally get wet (unless hosed or rain in extreme wind - hasnt happened since the tiling was done). The only way for water to get through is the grout that I can see. Is this normal? I hope not and that it can be resolved. The water that comes out is staining anything it falls on below, obviously lime from the screed or something. It's also now leaving rusty stains. I'm hoping from leaf litter on the balcony and not rusting reinforcing in the screed.

Cheers

[Master Splinter]

Grout should not be relied on to form a non permeable barrier - that's why there are waterproofing membranes under tiles. Grout is porous, and of course it has cracking issues anywhere there is movement...so it's best thought of as 'splash-resistant'.

[Oldsaltoz]

Almost all grouts will allow some water through, epoxy based grout is much better and sadly also much more expensive.
it's not uncommon for water to take some time to emerge at the bottom of the fall to the edge. However there should be no staining from the grout, levelling compound or tile glue as both should be rated for outdoor use.

Good luck. :)