Hello Sir,

i'm also planning on building a house with a concrete roof deck instead of the typical corrugated steel roof and was researching on the pro's and cons of this design. while researching i came across this discussion: roof deck waterproofing survey please - PinoyExchange

i believe this is very relevant to your need and can give you many ideas in waterproofing.

off topic...
aside from the leaking roof, did you ever notice your house to be "warmer". usually concrete walls absorb heat and they are not good in dissipating it. and they tend to release the absorbed heat during night times. can your share your experience with your house regarding this sir?

thank you...