(continued)

Many more concrete, non-propelled barges were mass-produced by assembly line building, being constructed from pre-cast sections made in various sites around the country from concrete placed in moulds and vibrated at high speed to 'shake it down', then moved to the erection yard for completion.
Except for bow and stern shapes, the concrete slabs were of standard shape and size, 7 ft x 3 ft x 2 inches thick.Only a little steel reinforcement was necessary and steel ends projected for the interlocking and knitting process when being assembled. However, a certain amount of reinforcing of the concrete for keelson, floors, frames and hatch coamings was also necessary.

The weight of the barge was 128 tons, made up of 174 pre-cast units and 12,25 tons of reinforcing steel. The deadweight capacity was 200 tons.
Those barges that worked on the canals and narrow rivers had moveable rudders with tillers, but those employed on the reaches of the River Thams were of the familiar swim-ended dumb barge form with budgett plate - a plate protruding af, on the centre-line and acting as a fixed rudder.
The Stem-type barges were 84.7 ft. long x 22.7 ft. deck width and 19.5 ft at the bottom; the Swim-type 86 ft x 24 ft. The hatch was 47.7 ft x 16 ft and the sides were fendered with elm timbering.
The first barge was laid down in May 1940; construction time being later worked down to seventy-four hours from launching one barge to launching the next from the same berth. Wates Ltd., Barrow-in-Furness, were major builders of these prefabricated barges; others were produced by Grays Ferrocrete Company, Tarrans and J. Lowe & Sons, of Liverpool.

All the barges were prefixed FB and numbered. Nearly 500 were constructed, of which some 200 could carry liquid cargo in bulk.

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That's all, a rather small part (otherwise I would not have typed it out...). Hope the info you are looking for is in there.