Forest Products Laboratory Discusses Uses Of \fhite Speck Lumber

Some recent observations on the presence of white speck (more accnrately and preferably termed rvhite pocket rot) in lumber have focussed attention on its use in building construction. The topic is of increased interest because of the present commercial harvesting of timber stands in which trees contain considerable amounts of white speck' Formerly trees of this type were often le{t to waste in the woods, or were not accessible to the logging industry. In the interest of conservation it is desirable to use lumber containing white speck rvhere use requirements permit.

There are many satisfactory uses {ollumber containing white speck. High strength is not generally required for sheathing, core stock, subfloors and roof boards, and white speck lumber may be used for these ptlrposes. When used for joists, studs, and framing in house construction, care should be taken to select a grade that rvill provide sufficient strength for the purpose intended.

Pending further examination of the subject, white speck lumber should not be put to structural uses that have a high strength requirement. As currently graded, white speck lumber is not admitted in the grades of lumber designed to meet such high strength requirements.

It is important that users understand clearly tl-re nature of white speck and the limitations imposed on the use of lumber containing it. White speck is caused by the fungus Fomes pini which destroys wood cell structure in progressive degrees. In its final stages the rot riddles the heartrvood with spindle-sl-raped pockets whcih are lined with strands of nearly pure cellulose. After the lumber containirrg Fomes pini has become continuously dry (less than fr percent moisture content, which is normal for housing

Vcn Nuys Yard Hcs New Owners

The Northwest Lumber Co., 14350 Bessemer Street, Van Nuys, Calif., was sold September 10 to John S. Moloney and Leo J. Ryder.

R. L. Tressler continues as manager of the yard. The telephone number is STate 5-0593.

lumber not exposed to the weather) the fungus will not progress further. If it becomes wet again, white speck lumber, like lumber free from tl-ris defect, is subject to decacy caused by other fungi.

Knots and other growth characteristics reduce strength according to their magnitude. White speck in the advanced stages of decay likewise materially reduces the strength of' wood in bending, compression, toughness, and stiffness. The reduction in strength is gradual, beginning just before the advanced stage is reached and increasing as decay progresses. U. S. Dept. Agr. Bull. 779 shows that, in the advanced stages of decay, bending strength is reduced as much as 50 percent, compared to clear lumber 'free of all defects. Likewise, compared to clear lumber, compression is reduced as much as 30 percent; impact as much as 40 percent; and total work in bending as much as 80 percent. Since lumber containing white speck provides lower strength values, commercial standards classify lumber containing'ivhite speck-as well as that ocntaining large knots, knot holes, shake, split, et cetera-into the lower grades which are not expected to furnish high working strength.

When high nail-holding power is a definite requirement, allorvance should be made for reduced nail-holding power. More nails or larger nails or both would be required to o'btain the same holding power.

For practical purposes the effect of Fomes pini in reducing the strength of lumber does not progress beyond the time at which the lumber is manufactured. Thus it is possible properly to classify and grade white speck lumber to meet specific use requirements at the time of manufacture.

Moves to New Offices

Charles E. Kendall, Southern California sales representative of Taylor Lumber Company, Eugene, Oregon, has moved into new offrces, Room 629 Petroleum Building, Los Angeles. The telephone number remains the same, PRospect 8770.