Piers, slope and the second truck

Three things move a modular install price more than the home does: how many piers it needs and how tall they are, how hard the block is to get a truck and crane onto, and whether the home comes in one module or two. Footings run $800 to $1,200 a pier in South East Queensland and a small single module sits on six to eight, a two-module home on twelve to eighteen. A steep block makes every pier taller and dearer and can add a geotechnical report. Delivery and crane is the widest line, $8,000 to $38,000, set by distance, crane size, reach and whether a street has to be closed. A second module means a second truck, a second lift and its own pier line.

Piers: the engineer counts them, the soil prices them

A structural engineer registered in Queensland designs the footings and the tie-down and certifies the design for the certifier. The count comes from the home's length and width and the loads; the type and depth come from the soil. A soil test classifies the site under AS 2870, from A and S for stable ground through M, H1 and H2 for reactive clay to E and P for the worst, and the more the ground moves the deeper the piers go. On a flat block with good soil a 8.4 m module sits on about ten piers at the bottom of the range. Reactive clay, fill or a flood level that lifts the floor push the price per pier toward the top.

Slope

A gentle slope means longer piers on the downhill side and a bit more steel and concrete. A steep block means tall piers, bracing between them, sometimes retaining, and a geotechnical engineer's report on slope stability, about $2,000 to $4,600, before the certifier will approve the footings. A flood overlay has the same effect from the other direction: QDC MP 3.5 sets the habitable floor at the defined flood level plus 300 mm of freeboard, so the home rises and the piers grow.

Getting it in

• Distance. Delivery across South East Queensland from a maker's yard runs about $1,900 to $4,100 a module ex GST. The Gold Coast and the Sunshine Coast are a longer run from most makers.
• Width. In Queensland a load wider than 3.5 m or longer than 25 m travels with a pilot vehicle. Most modules over 3.4 m wide need one, and the wider the home the more the escort and the permit cost.
• Crane. A small crane beside the spot for a morning is one bill. Reaching over the house, a long reach from the street, or a closed road with traffic control is another, and it is the up to $20,000 swing in the calculator. Overhead wires, trees and where the crane can stand are checked at the site visit.

The second truck

A home that comes in two modules needs two trucks and two lifts, a pier line under each module, services run between them, and the join itself: the marriage line, the flashing, the roof and wall join and the finish inside, with two to four more days on site. Joining alone runs $8,000 to $15,000. Two modules goes through it.

See it for your block

• Install cost calculator
• Check your block: slope, access and overlays
• How installs work, crane day included

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