Options for waterproofing – advice sought

Hi Strata Community,

I’d like referrals for two different aspects of waterproofing.

Some background. Small block; commercial promises occupies whole of ground floor (“shop”). Stairs to side of shop lead to common courtyard above shop. Courtyard contains another small staircase within it. Two units above front of shop; two units above rear of shop; courtyard forms open space between units and forms part roof of shop.

Shop constantly leaks in wet weather (unit owners pray for prolonged drought. Sorry farmers.). Unable at present to strip out shop to try to trace leaks from inside shop. Best guess is that water falling onto courtyard above shop is penetrating ceiling. Drain in centre of courtyard to carry water away.

First question:

Recommendations please for investigators who can try to locate source of leak. eg sending probes down drain to see if pipes cracked or into ceiling of shop to see if we can get to exact point of entry. This might narrow down the repairs we need to do.

Second question:

If we can’t locate exact point of water ingress, we may have to fall back onto waterproofing largest suspect – the courtyard floor. Initial idea is to rip up all tiles, re-waterpoof with either paint-on membrane or install waterproof layer and re-tile. Any ideas for alternative eg laying new waterproof coating over present tiles to wrap up walls to seal, then finishing this coating in an attractive way (eg stencilling on tiles)?

Looking for cheaper solutions than wholesale remodelling as unit block in area of rezoning and I hope we can sell to developers in short time (2 or so years) so a developer can start again on what was a pretty disastrous build (less then 20 years old and riddled with water penetration problems).

Thanks.