Our decking will be poured soon (framing is going in). A discussion came up about the mastic that'll go around the coping (only ~1/3 of the pool/spa perimeter)... and if it is needed. Our cement guy says he pours to the coping and it looks cleaner... everyone else has just sort of gone along with mastic but not 'explained' WHY you need it... so, is it needed? What does it do for you? We live in Southern CA and rarely ever (a couple nights a year) get frost on the grass... rain is... well, it can rain, but it's sporadic... so, what does the mastic do for us vs. just pouring the cement to the coping (quartzite flagstone).
Thanks! (if this belongs in another forum, lemme know)