The challenge associated with depending on Xypex for the waterproofing of roofs or other suspended slabs is the possibility of dynamically moving cracks and joints in these structures.
Horizontal slabs such as roofs can be subject to variable live loads. These can be snow loads that increase as the snow gets deeper (or gets rained on) or gets lighter as the snow
melts, wind loads that vary as the wind speed varies, pooled water loads that vary through rain events, etc. These variable live loads can cause the slab to flex and move ever so slightly and this movement can cause the cracks and joints in the slabs to also move.
Xypex is very effective at healing and waterproofing non-moving concrete including the hairline cracks that form but because Xypex takes days to weeks to heal a crack, if the crack moves on a fairly regular basis, these moving cracks may never heal. Thus while we are aware that Xypex is used to successfully waterproof roofs in many areas of the world we are very careful to ensure that, when an enquiry such as this one is received, we make those involved aware of the limitations of Xypex waterproofing. Generally we recommend a belt and suspenders approach like the one you used with a flexible membrane being the primary waterproofing system.
In terms of testing the existing installation to see if it is waterproof on its own there is no practical way I can think of that does not entail just watching the roof to see if leaks appear…….. This approach is much more acceptable during construction when leaks will only maybe wet some interior framing rather than in your situation where a leak can be quite destructive. Just testing a small piece of Xypex treated concrete will not tell you if there are moving cracks in your roof that will not heal with Xypex.
Please call me if you want to discuss this further – 604-273-5265.
Posted on 03 Apr 2017