I am an architect working on the detailing of a limestone stair for a church and have discussed the project with a few contractors, manufacturers, and a mechanical engineer. The upper landing is 9'x23' and there are 9 treads at 23' long. We have space for a boiler and have opted for a hydronic system due to the presumed lower operating costs. The dilemma is how to get the piping close enough to the surface of the treads to be treated.
The limestone fabricator is looking to create an L-shaped tread/riser with a uniform thickness of 3" due to our concern that we could not heat through a 6-1/2" thick solid limestone slab style tread.
Our thought was to place the hydronic tubing in a 2-1/2" mortar bed between the limestone above and the concrete formed stair below.
The problem is that the 6" bending radius limitation of the 5/8" diameter Pex will work for the upper landing but we will not be able to keep this within the mortar bed of the steps (90 degree bends, 2-1/2" mortar bed thickness.)
I am concerned that placing the tubing in the concrete stair below will be too far from the exposed surface of the step and will not be effective. Does anyone have any thoughts on this? Project is in NJ.