Bushcraft build · section drawing

Rocket mass stove, cut through the middle

All dimensions are in centimetres and measure the inside clear opening: the space the fire and gas travel through. Wall thickness goes outside these numbers, so size your formers to them. Heights are measured from the burn tunnel floor, which is level with the shelter floor.

floor sticks in exhaust out A 30 feed tube 110 riser height (80–120) 11 40 burn tunnel (30–40) 11 6 gap riser top → cooktop 5 gap riser → dome wall 20 20 mass over channel (15–25) 11 × 11 channel, climbs 10 into the bench channel run about 3.9 m with 2 bends (shortened at break) 11 125 above riser top feed tube hearth stone riser: 3 refractory + 8 insulation flat stone cooktop cob dome wall 10 light clay 10 dry stone, below the floor 10 dry stone cob + dense stone bench stone and cob all the way up cleanout plug top 2.35 m above the floor burn tunnel
Side section, 1 : 25 approx. The dashed orange line is the gas path: down the feed tube, along the burn tunnel, up the riser, over the top, down the gap inside the dome, through the bench, and out the chimney. The bench and the chimney are shortened at their breaks. The cleanout at the bottom of the dome sits in the face beside the feed tube, out of this cut.
10 light clay 10 dry stone floor 11 5–8 wall 6 slab 11 clear opening
Section A–A through the burn tunnel. Every section of the run keeps this same 11 × 11 opening.
  • Refractory mix: 1 clay to 1–2 sand, no fibre
  • Light clay insulation: clay slip + sawdust, grass or ash
  • Cob: 1 clay to 2–3 sand, plus fibre; pack dense stone into the bench
  • Flat stone slab (dry-land stone only)
  • Dry stone, under the light clay base and the bench
  • Fire and exhaust path
PartDrawnAllowed range and how it's measured
Feed tube, burn tunnel, riser, channel, chimney11 × 11Inside wall to inside wall. Never narrower anywhere along the run.
Feed tube height30Tunnel floor to top of the feed opening.
Burn tunnel length4030–40. Inside of the feed tube's back wall to inside of the riser's far wall.
Riser height11080–120, and at least twice the tunnel length. Tunnel floor to riser top lip.
Riser insulation88–10 of light clay around a 3 refractory wall.
Riser top to cooktop65–8 clear gap.
Riser to dome wall5About 5 clear gap all round.
Bench mass over channel2015–25, top of channel opening to bench surface.
Channel run3.9 mUp to 3–4 m with as few sharp bends as possible. Climbs 10 from the dome into the bench.
Chimney top+125At least 60 above the riser top lip, and 60 above the roof beside it. 2.35 m above the floor, stone and cob all the way up. No wood in the flue.
Base under the stove10 + 10Light clay over dry stone, below the floor, so the tunnel floor is level with the shelter floor.