Concrete Barges

Concrete barges float because of the sheer volume of water displaced by the barge. Acting in accordance with the laws of physics, the weight of water displaced equals the weight of the barge.

The barges are formed atop two steel cradles with a total of 12 wheels that run on railroad tracks which extend into the bay. A plywood deck is formed between the steel cradles, and wall forms are erected on the deck. The next phase is the installation of reinforcing steel. In a 16 x 36 barge, there is approximately 4000 lbs. of reinforcing, comprising #4 bars at 12” centers both ways in the walls and floor slab; #5 bars at 6” centers in top of the floor slab and #6 bars at the top and bottom of the walls.

Boat shaped barge for the SS Maggie South 40 Pier, Waldo Point Harbor, Sausalito, CA.

When reinforcing placement is complete and it has been inspected by the structural engineer, inside wall forms are installed, lined, plumbed and braced.

Home under construction for 27 Liberty Dock, Waldo Point Harbor, Sausalito, CA; New barge recently poured, ready for wall form removal and epoxy coating.

Concrete is usually poured beginning at 7:00 a.m. to take advantage of cooler weather. The pour takes from 2 to 4 hours, depending on the barge size. Design strength for the concrete is 4000 psi at 28 days, but this strength is usually attained at 7 days. The mix contains 7 sacks of cement per cubic yard of concrete and some plastecising admixtures and is delivered to the site with a maximum slump of 3” which is quite dry, but is workable because of the admixtures. A very important element of high concrete strength and minimum shrinkage is low water-to-cement ratio.

Wall forms can be removed several days after pouring. Then the “snap tie” (ties that hold the forms together) holes are plugged with a pre-cast cement cone and urethane caulking, then the walls receive two coats of cold tar epoxy coating.

The barge can be launched when the concrete reaches design strength which is normally about 7 days, but launching is usually 10-14 days after pouring.

As of August 1, 2008, the price for a new barge is $61 / sq.ft. All barges have epoxy coated reinforcing steel and the exterior of the walls is coated with two coats of polyurethane epoxy paint. A barge 16' x 32' x 6' would be $31,232. There is a minimum pricing size of 16x32x6 and a maximum pricing size of 20x46x6.

Sizes range from 112x26, 32x65, down to 12x20. Barges larger than 20x46x6 can be priced upon request.

Some concrete barges built by the military during WWII are being used as houseboat hulls, and with better concrete and two coats of cold tar epoxy, today’s barges can be expected to last at least 40 years. With the use of fusion coated reinforcing the life expectancy exceeds 80 years.

For a 200 year barge, epoxy coated reinforcing steel may be used. This adds substantially to the cost (about 20%) but produces a barge that will last for centuries. Of over 300 barges built by Aquamaison Inc., only four have used epoxy coated steel.

Aquamaison, Inc. began building concrete barges in 1978, and from that time on was having reinforcing steel designed and inspected by an engineer, taking concrete samples for testing, and casting into each barge a date, barge number, and the name “Aquamaison Inc.”

It was not until four years later that the County included these procedures in the Houseboat Code, for other builders to follow.

Each barge pour has continuous on-site monitoring to ensure a monolithic structure, a vital element for waterproofness and a quality product, for which Aquamaison Inc. is renowned.