19 June 2001
PROTECTING TIMBER PILES WITH POLYVINYL CHLORIDE
OR POLYETHYLENE WRAPPING
Problem: Either a new pile or pile butt is being installed that requires a protective
covering or marine borer deterioration has been discovered in an existing pile,
and further damage needs to be prevented. This method can also be used to
protect untreated piling from marine borer damage.
Description of Repairs: The following is summarized from Draft NFGS 02462,
Wood Marine Piling Flexible Plastic Encasement. Clean the surface of the pile to
remove all sharp or protruding objects that would penetrate or deform the plastic
wrapping on the pile.
"If a polyvinyl chloride (PVC) wrap is used on a relatively new creosoted
piling, first wrap a 1.0 mm (4-mil) polyethylene sheet around the pile to
protect the PVC wrap from the creosote. Install the PVC or polyethylene
(PE) wrap starting with the upper intertidal unit at least 30 cm (1 foot)
above mean high water (MHW). The lower units then overlap the upper
units and extend below the mudline. Tighten the PVC wrap using wood
poles and a ratchet wrench. Fasten the wrapper with aluminum alloy
bands around the top and bottom and with aluminum alloy nails along
the vertical joints (see Figure 6-3)."
Once the wrap is completed, backfill the area around the base of the pile.
Application: This method is widely used for preventing or arresting marine borer
attack. It is more economical than concrete encasement or pile repair or
replacement. Plastic wraps have been placed on creosoted piling in California to
prevent the migration of creosote into the water, thus avoiding any environmental
restrictions. Using a 3.8 mm (150-mil) polyethylene wrap in the intertidal area can
provide protection against abrasion.
Future Inspection Requirement: Look for punctures or tears in the plastic wrap;
any damage to wraps over untreated piles can result in rapid borer damage.