Medium-density housing has become a large share of New Zealand's residential building, especially in Auckland, Hamilton and Christchurch. Pricing a block of townhouses as a multiple of one house is a common mistake.
1. Fire and acoustic separations
Inter-tenancy walls need fire and acoustic ratings, often with multiple board layers, specific framing and sealed penetrations. Measure them as their own wall type.
2. Penetration seals
Every pipe, cable and duct through a fire separation needs a seal. On a six-unit block that can be hundreds of items.
3. Shared site works
Shared driveways, drainage, retaining and service connections are easy to under-allow. Price them as a common section, not per unit.
4. Roofs and junctions
Stepped roofs, parapets and junctions between units add flashings and membranes that a single house does not have.
5. Staging and preliminaries
Longer programmes mean more scaffolding hire, site management and temporary works. Preliminaries should reflect the actual programme.