Figure 48. Timber bulkhead at Bellihgham, Washington. Note projecting planks used for 

 tiebacks. 



Where it is difficult or impossible to excavate behind a row of king piles to the sheathing 

 depth required, timber sheet piles may be used in lieu of horizontal sheathing members. An 

 excellent technical guideline on this type of construction titled, "Bulkheads: Design and 

 Construction," was published by the American Wood Preservers Institute (AWPI), in its 

 monthly magazine, Wood Preserving News, in 1970. By permission of AWPI, the entire text, 

 tables, and figures of the three-part technical guideline are reproduced in Appendix B. 



All timber should be pressure-treated to avoid dryrot and destruction by living 

 organisms. In saltwater, coaltar-creosote treatment in accordance with applicable Federal 

 Specifications or AWPA Standard C18 should be specified. Without proper treatment, 

 timber construction soon falls into unsightly disrepair (Fig. 49), and may be compromised 

 to the point where it cannot fulfill its intended function. 



The structural properties of timber piles, wales, struts, and sheathing vary with the types 

 of timber used, with the nature of curing to which it was subjected, with its environmental 

 exposure in the structure, and sometimes by the type of preservative treatment used. These 

 properties, including allowable stresses under various loading conditions and environments, 

 are discussed in the Timber Construction Manual published by the American Institute of 

 Timber Construction (AITC), (1966). The standards for various types of lumber are listed in 

 Section 101-65, paragraph 3.5, of the publication; these are changed from time to time, and 



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