pushkins

Hi i have a question on concrete.if im pouring a slab 18/20 with footers 12'' what is the order of the gravel and plastic ,and should i remove any sand that may be present?
Also wanted to know if the rebar must be 3 inches from the sides of footer ,on the cradle .,any info is appreciated

I was reading your post regarding attic fans, could this lead to high temps in the duct from the AC? Could it be as simple as getting the ducts cleaned? Recently had a new compressor installed as we assumed that was the problem. The air from the AC is good as well as the pressure. I have had 3 people look at it. However from ac to ducts there is a heat up of the supply air by 10 degrees. How is this possible? My AC Guy said the attic is extremely hot and needs more ventalation. But the ducts have never been clean...could this be the problem? Thanks