- May 23, 2025
- 1
- 1
Hi all,
About a year ago, I commissioned a traditional offset smoker here in the UK and co-specced much of the design myself. I specified the look, cook chamber volume, and materials (8mm steel throughout), but I left the firebox sizing to the builder, assuming it would be scaled up to match. In hindsight, I’m now wondering whether the firebox may be undersized for the size of the chamber, and whether that’s the root of some fire performance issues.
Specs:
- Cook chamber: ~538L / 142 US gal / 118 UK gal internal volume (55" long, 27.5" diameter or approx. 140cm x 70cm)
- Material: 8mm steel throughout
- Firebox: 23.6" deep x 21.6" diameter (60cm x 55cm), semi-insulated design
- Stack: 5" diameter (approx. 12.7cm), 47" high (120cm) from collector, damper-controlled
- Fuel: Air-dried English oak (~11" splits), moisture typically 9–12%, some larger pieces closer to 18%
- Fire management tools: 4 Tel-Tru-style thermometers, Thermopro digital probes (grate and meat), anemometer to track airflow at the stack
What I'm experiencing:
- Fire behaves well early on after establishing a good coal bed (I use lump charcoal + kindling to start)
- Temps initially reach and even exceed 250°F / 121°C, but the chamber then tends to "settle" toward 200°F / 93°C unless I'm constantly intervening
- Interventions include breaking up the coal bed, stoking frequently, or even using a leaf blower to kick splits into flame
- Even with decent coal mass, splits sometimes smoulder rather than catch cleanly
- Anemometer shows airflow in the 1.7 to 2.6 m/s range with the stack 65% open and the firebox door cracked to the 4th notch
- Letting airflow exceed ~2.6 m/s often causes temps to drop, which led me to reduce stack draw slightly, but that still doesn’t solve the need for babysitting
What I’ve tried / learned from Reddit and experience:
- Running stack fully open appears to be the standard advice, and I plan to do that more consistently now
- Some have suggested my fire may be struggling due to sitting directly on the base of the firebox, so I’ll likely add a raised grate or expanded metal basket to improve air under the fire
- Ash buildup may be limiting airflow over time – I’ll monitor that more closely next time
- I’ve already been experimenting with split size and timing, but the "peak-and-wane" fire cycle still feels tight and unforgiving
My core question now: Do these symptoms sound like the firebox is simply too small for the chamber volume?
If so:
- Would you expect heat loss / inconsistent chamber temps despite good fire technique?
- Could a higher-volume firebox have helped the pit sustain temp more naturally?
- Any suggested retrofit options (e.g. increased intake, deeper coal bed)?
Thanks in advance!