Nice analysis, thanks! "Rigid" foam insulation board, less like plywood or track, is more compressible, and can absorb stress through minor, elastic deformation. The foam base will not be glued to the HCD underneath it, but the wooden "reverse skirting" will be attached to the door edges, not the foam edges (so the latter can be lifted out if need be.) The layout will be in a spare bedroom, and I keep the HVAC thermostat within a range of <25 degrees winter to summer, power outages notwithstanding. Thus, for an HCD layout, I'm not expecting any problems related to thermal expansion/contraction.
Are you sure that it's "about the same?" Or do you mean "approximately the same"? "About the same" means "more or less the same" while "approximately the same" means "give or take a little."
Inkaneer- like the picture. I used something similar to teach college students about thermal expansion... If you lay a straight track in the summer, 3000 miles long. What happens in the winter when it hits 20 below? In other years, I reversed it to laying the track in the winter. It is interesting to see which students understand and which do not...
