Yes correct. What you have on the market right now and off the shelf is SURFACE ONLY coating. Membrane only coating will only last for a few months due to high abrasiveness from sandy wind and rain water.

I used this type of product before. The effect is the same as this nano product where the water cannot seep in and become droplets. But after few months it not longer waterproof any more. The application is same using brush and the solution get seep inside cement, brick, marble, even tiles. Then problem is it cannot last. Beginning is fantastic. So I think if this nano product is same then it is useless, waste effort and money. Hope it is different and permanent?

It depends how you define the hairline crack and what is the width size. Can you include a picture here?



We use http://www.nanophos.com/en/SurfaPoreC_en.html to coat over concrete hairline crack.