I have a 18x20 second floor deck with three 6x6 support posts. Under the deck is a 40-year-old, well-settled, 12x20x6" concrete patio. The deck posts are set outside of the patio, set on footings underground - so the posts are buried. I'd like to extend the concrete patio so it matches the dimensions of the deck. That makes for a 6x20 extension.
One of my concerns with the concrete extension is that the new pour would surround the posts and I want to take the necessary precautions so I don't cause any future problems.
As for the extension, my plan is to implant short lengths of rebar into the side of the patio to help keep it and the new pour even. I will make sure the new pour is deep enough keeping the frost line in mind and using compacted aggregate underneath. Any thoughts or concerns with this approach?
I've read where I should use a 1/2" rubber wrap around the posts to accommodate post and/or concrete expansion. Is this advisable? Can I (or should I) seal the area with silicone to prevent water from seeping down?
Just to make it more interesting, and another of my concerns, is that the old patio drops about 5-6" over 12'. I'd like to reduce that slope. I was thinking of pouring the extension higher than the old patio and having it feather up the slope. Probably using an aggregate-less mix for the area on top of the old patio.
To finish it off, I'll either paint it or cover it with pavers - with the preference being the pavers.
I'd rather not demo the old patio, as some may suggest, but I'm open to all advice. The desired end result is that I want a more level, larger patio, under my deck, that will sit several inches above ground at the far end.
I have considered decking over the concrete but I have concerns with airflow, critters, and maintenance that I believe to outweigh the concerns of a concrete extension.
Thanks in advance for taking the time to read this and for responding.