Construction Details

Construction Materials

The road walls are dry stone revetments, backed by about 60cm of small stone rubble. They vary in height from 1.5 to 3.0 metres but are most commonly about 2 metres high. The pitch varies from 35 to 85 degrees but is most commonly 40-50 degrees and usually even from top to bottom of the wall. The stones are not brought to course and are poorly graded, but the face is very even, the joints well crossed and where well built and maintained, very stable. There are a few stone lined culverts and with stone lintels 1 metre long, which deliver stormwater and creeks from the other side of the road on to the beach. These are presumably the original culverts, most of which have been replaced with earthenware or concrete pipes. The rock used on the Portobello-Harrington Point Road is the local rock that has been quarried into in order to form the road. This rock varies from pink breccias to dark gray basalts. The rock used for the Aramoana Road is also the local volcanics but includes more grey Port Chalmers breccia. The stones were generally cleaved until they showed a suitable face and do not appear to have been trimmed by flaking. They are generally rather small - 50-20cm long and 10-22cm high. The wall is reasonably intact for about 32 kilometres around the harbour. The railway causeways are more massive, usually 3-4 metres high, a steeper pitch of 60-75 degrees, larger stones used, rougher face, stones not so well crossed on the more recent causeways, but well made and well chocked. They are built of Leith valley andesite and Port Chalmers breccia, the latter cleaving well into massive blocks. A photograph of the Arden Bay causeway under construction 19 November 1937, shows wooden profile frames in place to guide the wallers.

Notable Features

The length of the walls. They also represent a skill no longer generally available in the community.