Treated Wood Foundations for Buildings

The past several decades have seen a spectacular increase in the use of pole-type construction for many types of buildings. Interest is now spreading to the use of other types of wood foundation material. The need for uniformly high-quality treatment has become increasingly important if we are to regain the home buyers confidence in treated wood. The treating industry is faced with a dual challenge. First of all, it will be necessary to develop specifications for treatments that will provide not only a long average service life for the individual pieces in a charge or lot, but also a long absolute life for all pieces in the structure. Because of difficulty of repairing house foundations, a high uniformity of quality is needed. This is best achieved by high retentions and deep penetration. The Federal Specification TT-W-571 calls for a minimum assay retention in a prescribed boring assay zone. It is further required that in all round building poles or, round posts used in foundations, the penetration in each piece 10 inches or less in diameter shall be at least one-half the radius or a maximum of 2-1/2 inches. The specification encourages the use of rourd members for ground contact. However, the general building practice is to use squared poles. It is pointed out that even when there is no significant difference in the thoroughness of penetration, a given retention of creosote gives longer protection in round pine posts than all sapwood pine 2 by 4 stakes. This same difference between round and sawn material has been observed in field tests on other preservatives.

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