I will be installing a 700 lb. Woodstock Progress Hybrid on a hearth I built over an existing floor. My house was built in 1958 and has 2x10 solid pine floor joists with 3/4" solid pine subfloor and 3/4" solid oak flooring, all with no known or suspected deficiencies. I built the hearth on top of the oak flooring as it would have been a shame to remove it, plus I expect the 3/4" oak is adding considerable strength and/or rigidity to the entire installation. What I am not fully certain of is if the combined structure needs to be braced in any way. This area is over a basement and the 2x10 joists are spanning a little over 12' to 2x4 load bearing walls'. The stove & hearth is installed in the middle of this span and the hearth is 60" along the joist spans and 44" across the joist spans (so directly bearing on 3 of the 12' span joists). The hearth consists of 2 layers of 3/4" underlayment plywood screwed together in a 1 foot grid pattern for rigidity, 2 layers of 1/2" concrete backerboard for R value, and 1 layer of 1/4" ceramic tile The hearth is secured to the existing oak flooring / pine sublfoor with #10 deck screws at 9 evenly distributed locations. I expect the oak flooring and pine subflooring are further distributing this load but I am not an engineer. Does anyone have any education/training based feedback on whether this install is structurally acceptable without any additional joist support? With all due respect, I am not seeking any un-educated "I'd do this just to be safe" speculative recommendations. I could easily over-engineer additional bracing myself.