Advanced options
Stacked logs are ~40% air, so a tonne of wood (~2.5 m3 loose-thrown) stacks into ~1.4 m3: the store sizes here include stacking. Buying green (unseasoned) at half price and seasoning it yourself needs DOUBLE the store: this year's burning + next year's drying: the two-bay store is the wood burner's endgame. Open front facing the sun/wind, raised floor, roof overhang: a log store is a drying machine, not a cupboard.
What The Log Store Size Calculator Works Out
- Winter's wood: burning hours per week x weeks x the burn rate, which defaults to about 2.5 kg of logs an hour for a typical 5kW stove. A 20-hour-a-week, 20-week winter gets through a tonne of wood.
- Store size needed: the weight converted to solid volume at the wood's density, then multiplied by 1.4 because stacked logs are about 40% air. The suggested width is for a store 1 m deep and 1.8 m high, the common ready-made size.
- Store it right: a log store is a drying machine, not a cupboard. Raised on bearers, slatted sides, a roof with an overhang and an open front facing the sun and prevailing wind gets logs below 20% moisture in one to two summers.
- Burn rate (advanced): small 4kW to 5kW stoves use 2 kg to 3 kg an hour on a steady burn; 8kW room heaters and open fires can run 4 kg to 5 kg. Open fires waste most of it up the chimney.
- Wood density (advanced): seasoned oak, beech and ash are around 550 kg per solid m3, mixed loads 400 and softwoods 330. Denser wood means a smaller store for the same weight and longer burns per barrow-load.
- How you buy and bays (advanced): kiln-dried logs bought as needed want one winter's capacity. Buying green at roughly half the price and seasoning at home needs two bays, this winter's logs in one and next winter's drying in the other.
- Store depth and height (advanced): change the footprint to suit your wall. Logs are usually cut to 25 cm, so a 0.5 m deep store takes two rows; anything above 1.8 m high is awkward to stack safely.
- Winter fuel cost and seasoning saving (advanced): the stacked volume converted to loose-thrown cubic metres (x 1.4, which is how logs are sold by the load) at your kiln-dried and green prices. Kiln-dried typically costs GBP 120 to GBP 170 a loose m3 and green GBP 60 to GBP 90, so a GBP 200 two-bay store usually pays back in one or two winters.
- Heat into the room and gas comparison (advanced): seasoned wood gives about 4 kWh per kg; multiplied by the stove efficiency (65% to 80% for modern stoves, 20% for an open fire) that is the useful heat. The gas card prices the same heat through a 90% efficient boiler at the current unit rate, which is the honest test of whether logs are cheap fuel or an expensive pleasure.