2×8 Weight by Wood Type & Length • Complete Reference Chart
Roof Online Staff
Table of Contents
- 2×8 Weight Factors
- Actual Dimensions of a 2×8
- How to Calculate 2×8 Weight
- About This 2×8 Weight Chart
- Table: 2×8 Weight by Wood Type and Length
- Related Pages
- References for 2×8 Weight
2×8 Weight Factors
2×8 weight depends chiefly on the length of the board, the moisture content of the wood, and which tree species the lumber was made from. Pressure-treating the wood with preservative will also result in a small amount of additional weight after the board has had time to dry out after the treatment process.
Board Length: The length of the 2×8 will obviously be the biggest factor in determining 2×8 weight. This is self-explanatory.
Moisture Content: The moisture content of the wood is a big factor as well, but since all lumber tends to eventually arrive at the air-dried moisture content, variations in moisture content can be considered a temporary consideration.
Green lumber has a higher moisture content than air-dried lumber, and air-dried lumber has a higher moisture content than oven-dried lumber.
Green lumber has a moisture content above 19%. Depending on the actual moisture content of a particular piece of lumber, which can be well above 100% due to the way the moisture content of wood is calculated, green lumber can weigh more than 50% more than the same lumber when air-dried.
The typical weight of green lumber is roughly 10% to 30% more than the dried weight of lumber made from the same wood species.
Oven-dried wood (also called kiln-dried wood) normally starts off with a somewhat lower moisture content than air-dried wood, but tends to slowly absorb enough moisture from its environment to eventually reach the same moisture content as air-dried wood in the same environment.
Wood Species: The wood species the lumber comes from is the third important variable in determining 2×8 weight. A 14-foot-long air-dried 2×8 made out of Douglas Fir (coast type) will weigh about 36 pounds. A 14-foot-long air-dried 2×8 made out of Sitka Spruce should weigh around 29 and a half pounds. That’s a significant weight difference.
Pressure-Treatment: Pressure-treated 2×8’s can be remarkably heavy when you buy them. This is because when you find them in the store, they are usually freshly-treated, or have only been drying for a couple of weeks.
The water weight added to the wood during the pressure-treating process leads to freshly-treated boards weighing up to 75% more than the weight of untreated boards. This weight is temporary. The board will return (almost) to its original weight as it air-dries during the weeks or months after treatment.
2×8 weight for treated wood will be approximately 0.4% to 1.5% more than 2×8 weight for untreated wood from the same tree species after drying.
Actual Dimensions of a 2×8
A 2×8 is not actually two inches by eight inches, despite what it’s called. 2″ x 8″ are the nominal dimensions of the board.
The actual dimensions of a 2×8 are 1.5″ x 7.25″. Here’s why that is:
When a board is first milled, it actually does have the approximate width and depth (the nominal dimensions) that the final piece of lumber will be known by.
After the first rough cut, a two-by-eight is, in fact, about two inches by eight inches.
The next step in the milling process is to either air-dry or kiln-dry the green lumber, in order to reduce the moisture content of the wood. This causes the boards to shrink, reducing the actual dimensions. One reason this is done is to ensure that when the lumber is finished and sold its dimensions will be reasonably stable, and the board won’t continue to shrink significantly.
After drying, the boards are finished by being planed and smoothed, and having their corners slightly rounded.
This reduces the actual dimensions even further; it also lets the lumber producer be certain that the final product has the dimensions required by industry standards. In the case of a 2×8, the industry standard is 1.5″ x 7.25″.
How to Calculate 2×8 Weight
Step 1: Determine the wood type. To determine 2×8 weight, you need to know what kind of wood the 2×8 is made from.
Step 2: Look up the density of the wood. Once you know what type of wood you’re dealing with, look up the density of the wood in pounds per cubic foot. Weights of Various Woods Grown in the United States has an extensive table of wood species you can refer to, or there are plenty of other resources on the internet with the same information.
Step 3: Calculate the volume in cubic inches of a one-foot-long 2×8. This value will be used to figure out what percentage of a cubic foot a 1-foot-long 2×8 is. Since a 2×8 is 1.5 inches by 7.25 inches, a one-foot-long 2×8 will have a volume in cubic inches of 1.5 inches x 7.25 inches x 12 inches, or 130.5 cubic inches.
Step 4: Find what percentage of a cubic foot the volume of a one-foot-long 2×8 is. A cubic foot is equal to 12 inches x 12 inches x 12 inches, or 1,728 cubic inches. A 2×8 is 130.5 cubic inches per foot. 130.5 is 1/13.2414 of 1,728, or 7.5521% of a cubic foot (130.5/1728 x 100 = 7.5521).
Step 5. Find 7.5521% of the density in pounds per cubic foot of the wood species your 2×8 is made from. Let’s say you’re trying to figure out the weight of a 2×8 made out of Engelmann spruce. You look up the density of Engelmann spruce and see that it’s 23 pounds per cubic foot. Multiply 23 pounds by 0.075521 to get 1.736983 pounds. This is the weight per foot of a 2×8 made from Engelmann spruce.
Step 6: Multiply by the length of the 2×8. If your 2×8 is 12 feet long, multiply 12 by 1.736983 to get 20.843796 pounds. We’d round this to 20.84 pounds to be practical.
And there you go, a 12-foot Engelmann spruce 2×8 weighs 20.84 pounds.
About This 2×8 Weight Chart
The following table provides the approximate weight (dead load, self-weight) of 2×8’s produced from the various wood species and in the various lengths normally used in building construction in the US.
The values given in the table are meant to provide a general idea of typical 2×8 weights, and should not be used if precise values are needed for critical engineering calculations. The 2×8 weights are for air-dried lumber; kiln-dried lumber will weigh a little less, and green lumber can weigh a lot more.
When precision is necessary, always refer to the specification sheet for the actual, specific product you intend to use, or contact the technical department of the lumber producer or lumberyard.
You can see 2×8’s at the Home Depot. The approximate weights of the actual pieces of lumber for sale are often given in the product descriptions, so this can be a pretty good resource for calculating 2×8 weight.
Table: 2×8 Weight by Wood Type and Length
|2×8 Lumber Weight by Wood Type and Length|
|(Average Dry Weight, 12% Moisture Content)|
|Type of Wood||Length of 2×8 in Feet (2×8 × number of feet)|
|These are the most common wood types used in construction in North America.||Weight
|Pressure Treated Wood||Pressure-Treated (Freshly Treated)||5.51 lb||33.06 lb||44.08 lb||55.10 lb||66.12 lb||77.14 lb||88.16 lb|
|Pressure-Treated (After Air Drying)||3.14 lb||18.84 lb||25.12 lb||31.40 lb||37.68 lb||43.96 lb||50.24 lb|
|Cedar||Western Red Cedar||1.74 lb||10.44 lb||13.92 lb||17.40 lb||20.88 lb||24.36 lb||27.84 lb|
|Douglas Fir||Douglas Fir (Coast Type)||2.57 lb||15.42 lb||20.56 lb||25.70 lb||30.84 lb||35.98 lb||41.12 lb|
|Douglas Fir (Mountain Type)||2.27 lb||13.62 lb||18.16 lb||22.70 lb||27.24 lb||31.78 lb||36.32 lb|
|Fir||Noble Fir||1.96 lb||11.76 lb||15.68 lb||19.60 lb||23.52 lb||27.44 lb||31.36 lb|
|Subalpine Fir||1.74 lb||10.44 lb||13.92 lb||17.40 lb||20.88 lb||24.36 lb||27.84 lb|
|White Fir||1.96 lb||11.76 lb||15.68 lb||19.60 lb||23.52 lb||27.44 lb||31.36 lb|
|Hemlock||Mountain Hemlock||2.49 lb||14.94 lb||19.92 lb||24.90 lb||29.88 lb||34.86 lb||39.84 lb|
|Western Hemlock||2.19 lb||13.14 lb||17.52 lb||21.90 lb||26.28 lb||30.66 lb||35.04 lb|
|Larch||Western Larch||2.72 lb||16.32 lb||21.76 lb||27.20 lb||32.64 lb||38.08 lb||43.52 lb|
|Pine||Lodgepole Pine||2.19 lb||13.14 lb||17.52 lb||21.90 lb||26.28 lb||30.66 lb||35.04 lb|
|Ponderosa Pine||2.11 lb||12.66 lb||16.88 lb||21.10 lb||25.32 lb||29.54 lb||33.76 lb|
|Southern Yellow Pine (Loblolly)||2.87 lb||17.22 lb||22.96 lb||28.70 lb||34.44 lb||40.18 lb||45.92 lb|
|Southern Yellow Pine (Longleaf)||3.10 lb||18.60 lb||24.80 lb||31 lb||37.20 lb||43.40 lb||49.60 lb|
|Southern Yellow Pine (Shortleaf)||2.87 lb||17.22 lb||22.96 lb||28.70 lb||34.44 lb||40.18 lb||45.92 lb|
|Southern Yellow Pine (Slash)||3.63 lb||21.78 lb||29.04 lb||36.30 lb||43.56 lb||50.82 lb||58.08 lb|
|Spruce||Engelmann Spruce||1.74 lb||10.44 lb||13.92 lb||17.40 lb||20.88 lb||24.36 lb||27.84 lb|
|Sitka Spruce||2.11 lb||12.66 lb||16.88 lb||21.10 lb||25.32 lb||29.54 lb||33.76 lb|
|White Spruce||2.11 lb||12.66 lb||16.88 lb||21.10 lb||25.32 lb||29.54 lb||33.76 lb|
- Weight of a 2×4 by Wood Type and Length
- Weight of a 2×6 by Wood Type and Length
- Weight of a 2×10 by Wood Type and Length
- Weight of a 4×4 by Wood Type and Length
- Weight of Dimensional Lumber
- Weight of Glulam and LVL
- Weight of Plywood and OSB
- Weight of Pressure-Treated Lumber
- Weight of Roofing Materials
- Weights of Various Woods Grown in the United States
References for 2×8 Weight
- Weights of Various Woods Grown in the United States – Forest Products Laboratory, United States Forest Service, USDA
- Wood Handbook, Wood as an Engineering Material – Forest Products Laboratory, United States Forest Service, USDA