Placing 3'x4'x1" flagstone hearth pad

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New Member
Aug 22, 2021
Groton NY
I just picked up a 3'x4'x1" piece of flagstone to go under my regency wood stove. My house is under construction right now so i was planning on placing the stone on the subfloor but i have been advised the stone could crack under the weight of the wood stove. Are there any foam products i could put under the stone to evenly distribute the weight?


Staff member
Nov 18, 2005
South Puget Sound, WA
It's not the weight of the stove that may crack it. It's an uneveness or flexing under the slab that concentrates the weight on a less supported low spot. Make sure the subfloor is well supported so that there is no flexing of the subfloor under the stove. Then the slab could be bedded in a generous amount of silicone for cushioning and support. Or put down a sheet of plywood or cement board, then lay down a thick layer of bedding compound like latex modified thinset troweled with a 1/4" notched trowel and set the stone on that.

Bad LP

Minister of Fire
Nov 28, 2014
Northern Maine
Block the framing below as well as what was said already. In short treat the floor as you would for large size ceramic tiles.


Minister of Fire
Jan 19, 2017
Woolwich nj
this is one of the major disadvantages of flagstone. Its really uneven. Both top and bottom. Im going to be unpopular and say your going to be better off choosing a different material.. not trying to be a bummer.. pick something a little easier to work with thats probably not going to crack a couple year's down the line..