liquid rubber

I've been reading about epoxy and all the ways to seal plywood...has anyone ever used rubber roof coating or a product like this
http://www.jnkproducts.com/liquid-rubber.htm
Seems like an easy way to seal the exterior....would i need to worry about toxic fumes or off-gassing....? I plan to use spar varnish on the interior
http://www.jnkproducts.com/liquid-rubber.htm
Seems like an easy way to seal the exterior....would i need to worry about toxic fumes or off-gassing....? I plan to use spar varnish on the interior