Firewood – Understanding Some Basics

Firewood – Understanding Some Basics

Wood Qualities

When considering the type of wood to burn, some characteristics other than heat value are often important.  These characteristics include ease of splitting, ease of ignition and burning, extent of smoking, extent of sparking and coaling qualities.  The wood’s moisture content and the number of knots in it affect these other characteristics.  Table 1 presents some of the characteristics of commonly used fuelwoods.

If you cut your own firewood or split kindling and fuel logs, the splitting characteristics of wood are very important.  Short lengths of straight-grained, knot-free wood will easily split.  Green wood will often split more easily than dry wood.  However, red oak and locust split easier when dry than when green.  Cold or frozen wood can sometimes be easier to split.  Woods with interlocking or spiral grain such as elm and sycamore are very difficult to split. 

Measurement Units

The measurement units for the sale of firewood can be confusing.  It is usually measured by the standard cord – wood cut in 4 ft. lengths and stacked in a 4 ft. by 8 ft. pile.  There are 128 gross cubic ft. of wood, bark, and air space in a cord of wood but only 80 to 90 cubic ft. of solid wood.  Large, straight bolts will yield more solid wood per cord than small, crooked ones.  If you cut a standard cord into shorter lengths or split it, the wood will stack in less space because many crooks and air spaces are eliminated.

A face cord is a stack of wood 4 ft. high and 8 ft. long.  It can contain sticks (bolts) of any length.  A face cord usually contains bolts about 2 ft. long and is about one-half of a standard cord.

Other measurement units are also used.  If you are buying wood, be sure you have a clear understanding with the seller, preferably in writing, about the amount of wood being purchased.

Moisture Content

Firewood is sometimes sold by the “truck load” or by weight.  The amount in a load will vary with the truck’s bed space and weight-carrying capacity.  If you buy by weight or by the load, look for the driest wood possible.  The drier the wood, the more a truck can carry.  The moisture content of green wood varies from 70 to 140 percent.  Remember, the moisture content in green wood can exceed in weight the weight of the dry wood itself.  So, you want to buy as much wood as possible and as little water as possible.

A standard cord of green hardwood may weigh from 5,000 to 6,200 pounds, depending on the species.  Green hardwood has an average weight of approximately 5,800 pounds.  The buyer needs to know the type of truck hauling your firewood if buying a truck load.  A standard ½ ton truck without heavy duty springs can carry only about one-third of a cord.

Table 1. Quality Characteristics of Commonly Burned Firewood Species.

Meet the Author

Dr. Todd Shupe is the President of Wood Science Consulting, LLC. He is a well-recognized expert on wood forensics, wood preservation, wood decay and degradation, and wood species identification. He has a broad background in new product development, quality management, and marketing and sales in both the public and private sectors. For more information please visit DrToddShupe.com.

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