GROUND ANCHORED SOLUTION FOR A SAGGING BOARDWALK

Titan Deck Foot Anchors streamlined the repair of a 400-foot-long Pennsylvania boardwalk.

Chambersburg, Pennsylvania, contractor R. A. Hill Inc. won the bid, but now company vice president Jim Hill had a challenge on his hands: a deteriorating boardwalk running through a low-lying wet area along a south-central Pennsylvania stream.

In the bid documents were a set of plans with an unfamiliar structural detail. New crossbeams had been specced to reinforce the existing boardwalk framing, but instead of being supported by PT posts bearing on concrete footings (the boardwalk’s existing foundation system), the beams would bear on metal anchors manufactured by a Canadian company called Titan Building Products.

After a little online research and a few phone conversations with company founder and president Richard Bergman, Hill felt enough confidence in the system to place an initial order for 100 Titan Deck Foot anchors for the project.

There are actually three parts to each anchor: a galvanized steel post bracket, a cap plate, and an auger that is screwed through the cap plate into the ground.

The auger looks a little like a helical pile, but its main job is to resist uplift rather than provide bearing strength. That job is done by the cap plate, which the company says can resist loads of more than 19,000 pounds per square foot (an Intertek report is available here).

The beauty of the system – especially on this project – is that the auger can be installed with a hand-held impact driver, eliminating the need for heavy equipment.

The company makes both 24-inch-long and 36-inch-long augers, and says that the 24-inch-long auger is fine for most soil conditions. Hill decided to use the 36-inch-long version to provide better pull-out resistance in the soft soils along the stream.

Titan says that auger length doesn’t really affect the footing’s resistance to frost movement, and Hill expects that this boardwalk will rise and fall seasonally. But to prevent damage to post-beam connections, the anchors are engineered with what the company calls “Terra-Shift” technology.

These are basically slots instead of round holes in the brackets that allow the post to slide up and down rather than being locked in place by the fasteners when frost exerts a force on the deck.

Boardwalks Are Free Standing Structures

Hill says that his company ended up removing most of the old 2×6 PT boardwalk decking and replacing it, due to the amount of rot damage they found in the old 2×6 PT stock.

Where they could, they retained the 2×8 PT framing, which was in better shape than the decking; only seven joists needed to be replaced.

To reinforce the structure and minimize sagging, the crew installed 49 pairs of anchors along the length of the boardwalk. Located on either side of the boardwalk framing midspan between existing posts, the anchor pairs were tied together with 4×8 PT crossbeams, which support the joists.

In most locations, the crossbeams bear directly on the anchors, but where the ground dips away from the framing, 4×4 posts were used between the anchors and crossbeams.

Hill says that his crew unexpectedly discovered a number of existing PT posts that had deteriorated beyond repair.

Rather than replacing them with more PT posts, he placed a second order for another 53 anchors.

His reasoning? It would be a lot easier to transport relatively light steel hardware along the length of the boardwalk to make repairs instead of PT posts and heavy bags of concrete.

Another plus: Hill reports that it only took from 15 minutes to a ½-hour to install each anchor, which helped keep project costs under control.

The process involves minimal excavation, mainly to prep and level the area where the anchor is installed and put down a 2-inch to 3-inch layer of 1/2-inch crushed stone.

Because much of the boardwalk was close to grade, it was necessary to excavate a little deeper in some areas to fit the crossbeams and anchors underneath the existing framing. Cost for the Deck Foot anchor is about $54 each.