What NOT to use under your firebox

[Biz]

So my choice of flooring material seemed to make sense when I installed my 18x48" CDL evaporator in my new wood-floored sugarhouse 3 years ago - I chose cement board (brand name Durock), reasoning that cement is not flammable, and it wouldn't be that hot under there anyways, since all the heat goes up. There is no bottom on the arch so ashes fell on the cement board. The arch itself sat on concrete blocks to raise it up about a foot, so the ash pit was over a foot deep. And the floor was plenty sturdy with 4x8 joists and 2x6 full dimension pine planks, with extra frame support. So imagine my surprise when I went to clean the ashes out this year (my third season in this building) and found a softball-sized hole burned clear through the cement board and the 2x6's! Plus part of a 4x8 joist. I was lucky. Lesson learned, cement board is not the same thing as concrete! The new 2x5 Smokey Lake rig is getting set on something a little more durable, and fireproof. Maybe on some insulation too. Not really practical to pour a slab in my case.

Dave

[VTnewguy]

So my choice of flooring material seemed to make sense when I installed my 18x48" CDL evaporator in my new wood-floored sugarhouse 3 years ago - I chose cement board (brand name Durock), reasoning that cement is not flammable, and it wouldn't be that hot under there anyways, since all the heat goes up. There is no bottom on the arch so ashes fell on the cement board. The arch itself sat on concrete blocks to raise it up about a foot, so the ash pit was over a foot deep. And the floor was plenty sturdy with 4x8 joists and 2x6 full dimension pine planks, with extra frame support. So imagine my surprise when I went to clean the ashes out this year (my third season in this building) and found a softball-sized hole burned clear through the cement board and the 2x6's! Plus part of a 4x8 joist. I was lucky. Lesson learned, cement board is not the same thing as concrete! The new 2x5 Smokey Lake rig is getting set on something a little more durable, and fireproof. Maybe on some insulation too. Not really practical to pour a slab in my case.

Dave
You are lucky it didn't do more damage. Could have lost the whole shack. What are you going to put down now? Piece of metal?

[maple flats]

Before I had a concrete floor, I had a raised platform on the wooden floor of 8" concrete blocks, laid so the top and bottom was concrete and the "vent" holes in the blocks were free to breath. I then covered the top of the blocks with a 18 ga galvanized cover that fit over the whole platform, actually in 2 pcs. It extended down the edges 1.5" and where it over lapped the second piece it extended under the other 6". I made the hearth out in front 12" wider than the arch and it was 42" out in front of the doors. Directly under the arch I had 2 layers of 18 ga. galvanized. I used that for 3 seasons before I was able to pour the concrete floor. The metal under the arch was rough on the surface but was still in good shape after the 3 years. In that time I cleaned the ashes out of the base shortly after the season and I think that helped keep the metal in good condition.
But, when I finally added the concrete floor, I liked it far better.

[johnallin]

Before we started to erect anything, I had a concrete floor (with a drain) 2 courses of block all set on a rubble trench footer. I have never regretted the cement floor.

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