Floating a Boathouse

The bottom layer of each new cribbing was a mat of 6x6s bolted together with threaded rod.

The timbers were toe-screwed to the mat and to one another.

The assemblies could be floated out to deeper water as their weight and height increased.

Stones from the site were placed and compacted at each location the cribbing would be positioned.

A 6x6 beam served as a pile driver to compact the stones. Depth was checked using a furring strip.

Concrete blocks and timbers needed to be piled on top of the cribbing to make it sink.

A cable and turnbuckly kept the building from racking as it was lifted.

A steel angle was installed on the outside of the east wall to spread the load from the turnbuckle assembly over the top plates and several second-floor joists.

The author threaded the needle beams under the structure, resting the ends of the beams on the cribbing. Blocks set on a lower tier of cribbing supported the jacks while the crew raised the needle beam until it made contact with the 6x6 support beams under the floor.

Bottle jacks did the lifting, and screw jack sheld the needle beams while the bottle jacks were repositioned.

The existing 6x6 support beam on the west side of the boathouse developed a sag as the needle beam was raised, so the crew we added smaller, less elaborate supports at two other places along that side.

A couple of spreaders across the boat bay stabilized the bottom of the wall.

Solid blocking replaced shims to carry the load over the coming winter.

With the cables and spreaders left in place, the boathouse was stabilized enough to make it through the winter. In the spring, a stronger, more permanent foundation will be installed as phase 2 of the project.

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