materials
high strength concrete
douglas fir 2x4 and 2x6 (for framing)
fire brick
gravel
lava rock
mortar mix
process
building the formwork
cut eight 2x4’s and eight 2x6’s and built a square, bracing the outer sides with scrap wood
cut smaller lengths for the inner formwork, bracing the insides with scrap wood
laid a layer gravel to level the ground and placed the formwork in desired place
concrete
before pouring concrete, we added vertical and horizontal reebar pieces + two pvc pipes set between the outer and inner layer for ventilation when the fire’s burning
poured foundation concrete layer (6 in) + vibrated to eliminate air pockets and let sure overnight
laid fire brick with mortar and let cure overnight
poured remaining layer of concrete + vibrated
screeded the concrete top layer with wood then floated to finish
let cure for one week then removed formwork with crowbar
laid 1/2 foot of lava rock
