FP-96 English Version - Eastern Federal Lands Highway Division

Section 557Where the space between the bracing and the cap or pile is over 2 inches, usewooden shims of the proper thickness. Fabricate the wooden shims fromwhite oak or from the same treated wood used in the structure. Do not usebuilt-up wooden shims. Make wooden shims from a single piece of lumberwith the width not less than 4 inches and the length not less than the width ofthe bracing measured along the cap or pile. Do not adze, trim, or cut anytreated member to avoid the use of shims.557.13 Stringers. Size stringers at bearings and place in position so thatknots near edges are in the top portions of the stringers.Outside stringers may have butt joints with the ends cut on a taper. Lap interiorstringers to take bearing over the full width of the floor beam or cap ateach end. Separate the lapped ends of untreated stringers by at least 0.50inches for air circulation. Securely fasten the lapped ends with drift bolts asrequired. Stagger the joints where stringers are 2 panels in length.Securely toenail cross-bridging between stringers with at least 2 nails in eachend. Cut all cross-bridging members for a full bearing at each end against thesides of the stringers. Place cross-bridging at the center of each span. Ifblocking is used, make it fit snugly and hold in place as required.557.14 Plank Floors. Use plank that is surfaced on four sides (S4S).Single-ply timber floors consist of a single thickness of planks supported onstringers. Lay the planks heart side down with 0.25 inches space betweenthem for seasoned material and with tight joints for unseasoned material.Spike each plank securely to each stringer. Carefully grade the planks as tothickness and lay so that no 2 adjacent planks vary in thickness by more than0.063 inches.Two-ply timber floors consist of 2 layers of flooring supported on stringers.Pressure treat the lower layer with creosote oil. Lay the top layer either diagonallyor parallel to the centerline of roadway as required. Securely fasten eachfloor piece to the lower layer. Stagger joints at least 3 feet. Where the toplayer is placed parallel to the centerline of the roadway, use special care tosecurely fasten the ends of the flooring. Bevel the ends of top layer membersat each end of the structure.460