How do you build a bridge in timber?

The wooden road bridge is built of massive laminated timber beams made by gluing several laminated timber beams in parallel. The beams are fixed to each other as construction proceeds.
Holes are drilled through the beams to receive metal ties which are tightened to a strain of 15 tonnes. At that point, the entire bridge deck begins to act as a single load-bearing panel.
Water-proofing is laid on top of the deck with a 110-mm wearing layer of asphalt on top of that. On bridges for lightweight traffic, the wearing layer is 80-mm thick.
The balustrades are screwed to stainless steel fixings in the joints between the beam structures. These fixings are always dimensioned to be weaker than the load-bearing structure so that any collision with the balustrade does not have a deleterious effect on the structure. If screwed joints are used they can be easily renewed when necessary. The balustrade construction is a standard detail also used in other bridges.
The actual protection is given by separate wood cladding to provide a wearing layer which can be easily renewed when required. The load-bearing structures can be painted.