According to Isambard Brunel Junior, the viaduct was typical of his father's numerous viaducts, especially those that were built on coastal lines for the SWR. It had seventeen fixed spans of similar size and was built of timber. It was 750 ft long. To prevent river traffic being obstructed, the viaduct had a 40 ft opening swing bridge at the Swansea (east) end. As constructed, it was supported on timber piles driven 14 feet into the sand and clay bed of the river. The piles were arranged in groups of three, across the width of the viaduct. Above them, a timber deck was laid to carry a double track; the deck rested on timber baulks.