2 questions -- 2 connect new/old concrete patios or not 2 AND pour once or twice?

First off, I just want to say ‘thank you’ to all of those whom have asked questions and posted replies previously – in searching the forums, I have answered most of my newbie questions and revised my thinking on my deck/patio/footing plans.

I am building a small deck (11x9) to replace a failing landing & stairs at the rear of my house. The existing landing/stairs were constructed by regular 2x wood and supported by nailing a ledger into plywood (w/o any backing whatsoever) and rested on top of an existing concrete patio – like I said, it needs to be replaced.

The existing patio’s shape is roughly parallel to my house, growing wider as it expands towards the rear of house – total length is 30’ but width varies from 4 – 9’ – the depth varies. It is actually composed of (top to bottom) ¼” slate tiles cemented into 1-2” of mortar/cement, 4-7” of asphalt, 4-5” of un-reinforced concrete, which is on top of a 6” of gravel. How do I know this? I dug through all of this to prep for the footings for the new deck (4’ to get below the frost line). The patio, as you’d guess, looks like hell: 75% of the tiles have popped off and the whole thing pitches in two/three directions (none towards the house foundation surprisingly).

So here are my questions:

- I want to cover the existing patio (yet another layer!) to level the surface and provide a neat appearance to the whole area. I plan on pulling the remaining slate tiles off and clean (sweep, pressure wash, and blow with compressed air) the patio surface. The depth of the new layer will range from 3” next to the house foundation, to 4-6” at various points on the existing patio, to 8-10” at the new edge I am building to define the new patio (it surrounds the existing patio layers). I plan on using expansion strips next to the foundation, wire mesh (and fiber mesh added to concrete mix) across the slab, and rebar to build up and strengthen the edge [I will be constructing wood forms to define the new edge as well].

Choices: Do I “paint” the patio surface with an epoxy coating to prevent the new top layer from bonding with the lower layers OR do I want to bond the whole thing together by sinking (glued w/ epoxy) rebar vertically to connect all the layers together?

- Can I have the ready-mix delivered to fill both the Quik-tubes for my deck footings AND cover the existing patio at the same time. Is this possible? It means the inside and outside of the tubes will be curing at the same time. Would the wetness on both sides to the tube soften the tube to the point where the top of each footing “bends” before the concrete sets up? I figure that all I have to do with the tubes is sink the J-bolt when the time is right so I (and helpers) can work on screeding, floating, etc the patio.

I think that’s it for my questions so far – I am sure I will have more as the project moves forward.

 

It sounds like a heck of a mess to me, but you could pour over it if you've got the room.
I would lay down plastic sheeting or roofer's felt paper on top of the old slab to act as a bond breaker. That's what we do when pouring a new slab over an old one. That way, any cracks in the existing slab will not transfer up through the new one.
The expansion joint, wire, fiber, and rebar are all good ideas, though maybe overkill.
Pouring on both sides of the form tube won't cause the tube to become soft. However, you will see the tube in the finished product since it is poured in, and being paper it will eventually disintegrate, leaving a void. Good luck.

Pecos

 

If the existing concrete/asphalt mess slopes in several directions and the tiles have popped off, I suspect you may have a variation in soil support and you could just be adding another layer that may crack and have the same different drainage paterns mirroed through.

You may want to look into getting rid of the mess and just put in a good, uniform compacted gravel base and 4" of concrete. - More money, but a better chance to have a good patio in the future.

Dick

 

Sometimes you just have to admit defeat. Rip it out and do it right.