Questions: do i need wood separating the existing foundation and the new porch? I have an existing small cement porch. Do i need to put boards separating as well? I have a very hard soul here in central tx. Do i need to layer with pea gravel?
You can use a wood expansion joint but they make an asphalt based expansion joint that will last longer. It's there to allow the different pours to move independently and not cause damage. In central Texas, depending on the exact location, you may be sitting on the Houston Black Clay which moves a lot between the wet and dry seasons. It's advisable to use a #2 base under the slab of a PI of 17 or less. If you have pea gravel at hand, it can also be used but the #2 base is the standard.