I am going to add to my existing 10' x 16' concrete slab in the rear of my house and add a 16'x 24' enclosed room, how deep should I pour concrete in the new areas and should I secure my beams to concrete or should I sink them in the gound, Im a dock builder and this is the constrution I know. should I link the two slab together using rebarb or not? The only load on these walls should be the load of its roof.

Do not bother trying to connect the slabs, allow them to be free to float seoarte from each other. You need at least 4" of concrete with rebard or steel screen set 2" down inside. This is poured over5" bed of 3/4 rock and fines that have been leveled and compacted.

Is this a room or a patio enclosure?

If this is a room you need a foundation, which could be a lot of thing, depending on location and code..

Call you local building dept

Matt, your overall thickness should be at least 4" thick as ballenger stated. But where there is a load to bear, such as walls, there should be beams dug. On residential construction this is usually 1'x1' all the way around the perimeter centered under the walls. You may reduce this considerably if the load isn't too great. Also, a rebar beam should be laid into ditches and connected at the corners and connected to your wire mesh or rebar reinforcement grid. A lot of work but well worth it in the end. Hope this helps... good luck... Roland

Sounds like a fun project. If I was doing it I would definitely pin the two slabs together by drilling horizontally into the existing slab at it's leading edge and inserting short pieces of reinforcing bar (rebar). You can epoxy the rebar into the holes that you drilled for extra resistance to pull out forces. Also, at the outside corners of the new slab I would use a Post Hole Digger (I have a Ph.D!) to go down a ways until you hit UNDISTURBED SOIL. Any foundation should be either laid on undisturbed soil or should be engineered to prevent uneven settling. As a previous responder stated it is probably a good idea to make grade beams at the perimeter of the new slab through the use of rebar that is wired together at the corners and helps keep it all together. Concrete is very strong in compression but pretty weak under tension. That is why rebar is necessary; it gives the concrete strength to 'bridge'.

You can do it, I hope we helped!