Green Lumber vs. Dry Lumber

Pole Barn Guru Blog

Green Lumber

Need a piece of lumber? In most of the United States, you get one from your local lumber yard or “big box” store and do not have a choice as to whether the lumber is “green” (moisture content of over 19%) or dry. For the most part, what is available at the retail level is a regional dictate.

Historically, the green vs. dry battle has been a point of contention.

A great deal of attention was given at the Forest Products Laboratory in 1946 to problems arising from the use of green lumber in building construction. Sharp controversy developed between the Laboratory and that portion of the lumber industry which customarily manufactured and shipped unseasoned (green) lumber.

The statement, since widely quoted, “we still have not learned how to build good houses of unseasoned lumber” was made in a Laboratory report which was later withdrawn. An extensive “Program to Reduce Use of Green Lumber in Housing” was planned at the Laboratory, but never implemented. Although size standards were not a major part of the controversy, shrinkage in service was given as the principal drawback to the use of green construction lumber, thus emphasizing the relation of size to moisture content.

At about the same time was the case of the home owner in Virginia who sued for damages resulting from the use of green lumber in building his house. The court awarded him some $8,000 damages, but the award was set aside on appeal to a higher court.

There was also sharp controversy about whether or not building codes could legally set maximum moisture content values in lumber used in building construction. The argument was advanced that health and safety do not require dry lumber, and the building law could not go beyond health and safety requirements.

You may ask… why is green lumber even used? It is less expensive to produce green lumber than dry. Green lumber is softer than seasoned wood, it can be cut more easily, is not as likely to split and nails drive into it more easily.

A number of problems can result from the use of green lumber. Nail “pops” – as framing members dry and shrink, gaps are created between nailed together framing members, as well as between exterior or interior sheathing and framing members. Mold can begin to grow on green lumber before it is even used in construction. Airborne mold spores are found almost everywhere, and they can easily cause mold growth on wet wood surfaces.

In exposed areas, green lumber can be difficult to paint or stain, sap within the wood oozes out and causes discoloration and gaps between members (such as fascias) can result.

As it dries, wood shrinks considerably, and is prone to both “warp” and “check” (crack). Used in construction, problems may arise including warping the underlying structure and causing structural instability. Unlike lumber which has been dried at the mill, green lumber has not been treated with any substances which are designed to promote water and insect resistance. Green lumber is more subject to rot, and it can be viewed as a buffet by insects.

More often than not, the use of green lumber for framing material comes from lack of knowledge by the end user. For buildings where the finished quality makes a difference, dry lumber is the only sensible choice.

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11 thoughts on “Green Lumber vs. Dry Lumber

  1. Kairi Gainsborough

    It is really interesting how much controversy there is around using green lumber as a building material. I can see how softer wood and lower prices may be appealing. However, I would assume that most people look for treated wood when using it for any sort of heavy construction. You made a good point about how people using untreated wood are most likely inexperienced. If I ever decide to build on my property, I will know what to look for in my lumber now.

    Reply
  2. Ridley Fitzgerald

    It’s good to know more about what type of lumber is used. It does sound like green lumber shouldn’t even be used, although it does have some benefits. So, are homes always made from dried wood, or does it just depend?

    Reply
    1. admin Post author

      Always nice to get a comment from a lumberyard which has been in business for over 50 years! Thank you for being a reader.

      There are some markets in which the primary lumber for all purposes is green – Oregon west of the Cascades, most of California, parts of Arizona and New Jersey. With the issues of shrinkage of green lumber, one would think dry lumber would be used everywhere – but it is an economic decision in which pocketing greater profits outweighs the quality of the finished product.

      Reply
    2. Jeanna

      I don’t think it is that “cut and dry.” My understanding is that all homes over 100 years old were built out of green lumber. You cut the trees around you and you built your house. No one kild dried their lumber.
      Most “kiln dried” lumbar is not properly dried. Center pieces are much wetter then outer pieces. There is lots of warped wood at the lumber yard that was “kiln dried. ” Warping greatly depends on grain. So care does need to be taken in choosing your pieces in the most structurally strained areas.
      Where I would want dried wood is where you are concerned about laps and gaps, like flooring or siding on internal walls.

      Reply
      1. admin Post author

        Two things…

        One: Our ancestors were patient, they air dried the wood properly, then brought it inside and completed the drying. This took a couple of years, but it worked fine.

        Two: Houses were not centrally heated or air conditioned, therefore wood didn’t need to be as dry as it does in many modern homes.

        Can you provide verifiable sources for your statement of “most kiln dried lumber is not properly dried”?

        Reply
  3. Cory Petrachek

    Can I use green rough cut lumber to make a gazebo and just spray it down with a wood sealer after I’m done construction?

    Reply
    1. admin Post author

      Can you and should you are two different things. Professionally I could never recommend the use of green lumber for any structural application.

      Reply
  4. Wilma Colekessian

    We have a green lumber patio table top. Is it safe to eat on that wood? What if a piece of food goes on the table and the children just pick it up and put it in their mouth.
    OR IS THE MATERIAL USED POISONOUS?

    Reply
    1. admin Post author

      If “green” means not kiln dried, then it is perfectly safe. If “green” means it is pressure preservative treated, then no.

      Reply
  5. Wes T

    What does the moisture content need to be in wood before it is considered dry lumber? Before it would be considered safe to build with.

    Reply

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