Rock elm firewood: BTU, weight and seasoning

Heat per cord

Rock elm is a hardwood. At 20% moisture, a full cord holds about 27.5 million BTU of heat (29.1 gigajoules). Wetter wood gives less, because part of the heat goes into boiling off the water.

That ranks rock elm 223rd of the 558 species in our tables, from the hottest down.

Weight and density

A full cord of seasoned rock elm (20% moisture) weighs about 4,480 lb (2,030 kg). Freshly cut, the same cord weighs about 5,370 lb (2,440 kg): the difference is water you don't want to burn.

Its specific gravity, a measure of density, is 0.75. Denser wood packs more heat into each cord.

Seasoning time

Split and stacked off the ground, rock elm needs at least 11 months to dry to about 20% moisture.

Wood dries faster once it is split and stacked with air around it. A moisture meter on a fresh split face tells you when it is ready.

How it burns

• Ash: low
• Coals: very high
• Burn time: very long

We rate rock elm 6 out of 10 as firewood: a good choice.

Similar firewood

Other species to compare with rock elm:

• American elm: 20.4 million BTU per cord
• Cedar elm: 23.9 million BTU per cord
• Dutch elm: 21.0 million BTU per cord
• English elm: 20.6 million BTU per cord

Where these numbers come from

The heat and weight figures come from our firewood tables, worked out the same way for every species at 20% moisture. See how we calculate them.

Questions