We're building an outside patio with a 625 sq. ft. second floor deck. Might there be a weight concern with the 6 lb. weight per tile + the weight of rain water that can be held in the porous tile?

We wouldn't recommend using these pavers on a second-floor patio since they are semi-permeable and would allow water to still flow to the balcony below. Our Nitro Rolls would work great for this use. These rolls are UV resistant and non-porous preventing water from penetrating to the balcony below.