Forestry & Conservation Study: Timber and Housing
In 1950, the average home in the US was 983 square foot in size. During the housing boom of
the mid 2000’s, house sizes swelled to over 2340 sf. As homes get larger, more trees are
harvested to keep up with demand. The amount of lumber that can be harvested from a tree
depends upon the height and diameter of the tree. A useful measure of tree volume is a unit
called the board foot. One board foot has a volume equal to that of a block of wood that is 12 in
x 12 in x 1 in. You will be calculating the amount of lumber produced in a 1/100th acre plot and
extrapolating that information into the number of trees needed to construct a house.
Materials
Clinometer
Pencil and paper
Tape measure
Procedure
1. Select a 21 ft x 21 ft area (1/100th of an acre). Walk a distance away from a tree so that
the sight from through clinometer to the top of the tree measures a 45o angle. Measure
the distance from the base of the tree. Record in feet. (*12 inches = 1 foot)
2. Measure the circumference at breast height of the tree you are studying (in inches).
Record.
3. Repeat with the remaining trees in your area.
Calculations:
1. Height of Tree = Distance from tree (at 45o) + Height to Eye Level of measurer
2. Circumference =  x diameter. Calculate Diameter at Breast Height; convert into feet.
3. Radius = diameter/2 ; Area of a circle is (A=  r2) . Since a tree is almost circular, use this
formula to find the area of a cross section of your tree at DBH (diameter at breast height).
4. Use the formula to calculate how many cubic feet (volume) of lumber are in your tree.
Cubic Feet = Area (ft) x Height (ft) / 4
(note: 4 is used to account for the taper of the tree)
5. There are 12 board feet of lumber for every one cubic foot, so multiply volume by 12.
You have calculated how many board feet of lumber your tree has.
Tree
Distance
from
tree (ft)
Height
of tree
(ft)
Circum. at
breast height
(in)
DBH
(ft)
Area
Volume of
Tree (ft3)
Board feet
1
2
3
4
5
6
7
8
9
10
Total Board-Feet in Area
Average Board-Feet/Tree in Area
Analysis:
1. This activity was done in a 1/100th of an acre. How many board-feet would be produced
per acre from an area like this?
2. A 2000 square-foot home (the Moorestown average) uses about 13,000 board feet of
lumber. Using the average of your area, how many trees would it take to build a house
that size? How many acres would that be? How many acres of trees must be felled to
construct a 100 unit housing development?
3. The cost of lumber in 2010 was $283/1000 board-feet. What is the value of the timber in
the plot of land you measured? What’s the value in one acre of forest?
4. In 1950 the average US home was about 950 square foot. House sizes swelled in the
mid-2000s, with the average home reaching a size of high of 2349 sf in 2004. How many
times more lumber was needed to produce the average home in 2004 compared to 1950?
5. Identify and describe three environmental issues that are associated with the timber
industry. What could be done to help reduce the harvesting of wood for house
construction?