A big fall in engineering construction and apartment building has pushed the entire construction sector into contraction and a 20-month low in October.

The Ai Group and Housing Industry Association Performance of Construction Index (PCI) fell 5.5 points to 45.9 points in the month, from 51.8 points in August. A level below 50 points indicates activity in the sector is winding down. The biggest mover was engineering, which slumped 13.7 points to 44.3…