19 June 2001
TR-4: PARTIAL POSTING OF DAMAGED PILE WITH NEW PILE BUTT
Problem: Top of pile has rotted or has major insect damage. No other major
Description of Repairs: Cut the pile below the damaged, rotted, or insect
infested area. Cut the pile butt to length and shape head to fit pile cap (if
required). See Figure 6-4 for two methods of interfacing pile butt with pile cap.
Make the joint with two pretreated timber fishplates bolted to existing pile and pile
butt using 2.55 mm (100 mil) galvanized bolts. Treat the ends of all cuts with
creosote. Treat bolt holes with the same wood preservative as used for the pile
butt. Place shims between new pile butt head and pile cap. Bolt pile or fishplates,
depending on the method selected, to pile cap.
When adjacent timber piles have been repaired using either posting or fishplating
techniques, it is necessary to provide some resistance to lateral loads imposed
on the structure. This can be done by installing X-bracing between piles, as
illustrated in Figure 6-4. Treated timbers are fastened high on one pile and low
on the adjacent pile, forming an X pattern. Where X-bracing crosses, a timber
spacer should be bolted between the bracing pieces to shorten the unsupported
length of span.
Application: This method works well where not many piles need repair. This
method may be more expensive than replacing the pile. The cause of damage,
e.g., water entrapment, must be remedied before using this method.
Future Inspection Requirement: Even with X-bracing, weak joints will exist
where column buckling may occur. All splices and holes below MHW may be
subject to accelerated marine borer attack. This may be offset by adding a PVC
wrap around the splice. Above MHW these areas are subject to accelerated