We received an email with some questions that are very common, and it seemed like sharing the answers could be helpful to others looking into WarmFörm for their projects.
• For utilities, are these generally set in the subsoil prior to beginning the gravel base install or is it best to install utilities within the gravel layer?
• Do you recommend a geotextile layer over subsoil prior to gravel or is this overkill?
• Is there a reason to keep the vapor barrier over the first layer of foam and not over the top layer, or is this just for ease of keeping the vapor barrier flat?
• Utilities. There is no single way for this. Some people have installed their utilities in the soil, some in the stone base (although utilities in the stone base have to transition to the soil outside the perimeter of the stone base), but in my mind getting the rough-in in place before the stone makes the most sense. Then you are not digging into the stone, disturbing your final level of that work.
• Geotextile between soil and stone base is not required. Geotextile is usually meant to create a drainage plane on a vertical surface. What you are really asking about is a filter fabric to keep soils from intruding into the stone. Still, not required as you are not going to have a flow of water across this border as you do when you are setting up a drainage area next to a footing at the base of a foundation wall.
• The vapor barrier is located at the first layer of foam just for ease of installation, as you suggested. You are working on a flat surface, and aside from some hospital corners its very easy to layout. But some customers have been concerned about puncturing the membrane with the foam spikes, and have put the vapor sheet over the top, and dealt with the more involved fitting that is entailed.