The Difference between Unibuild “Off Site” Modular and Conventional Construction

The first Unibuild off-site modular home was built in Canberra in 1968. In 1969 we relocated to Perth, Western Australia, and designed and constructed many Unibuild modular masonry buildings requiring the labour of bricklayers. In the early 70’s Western Australia was booming and bricklayers were in short supply. They would quote a job, lay a couple of hundred blocks then demand a review of rates upwards.

Unibuild decided to eliminate the masonry trade in favour of its modular, insulated precast concrete walling components. In a public demonstration we commenced construction of two projects of identical design on the same day. One was the usual Unibuild modular masonry construction, the second was Unibuild’s first precast off-site modular construction. The following photographs show the advantages of Unibuild off-site prefabrication.

1410_050   Unibuild’s first truck load of insulated wall panels leaving for the site.

1410_034    Construction progress of the off-site modular house after seven days.

1410_067    Construction progress of the conventional masonry house after seven days.


Modular Construction:

  • Takes only a few weeks to complete the entire project on site, depending on size.
  • In the planning stage, off-site components are fully detailed to fit the specific needs of the customer’ project. (Each trade his its own detailed plan).
  • Off-site factory space is used to manufactures all the structural components
  • The only site work carried out are footing pads, sewerage and drainage works completed before the structural components arrive at the site.
  • A crane erects the prefabricated components in 1-2 days. Add doors and windows and lock up after 4-5 days. The job is now weather proof.
  • The interior trades, electrician, plumber and painter can all work together to complete the project.
  • Nil or only minimum scaffolding is required
  • Landscaping, driveways and paving can follow but are not critical trades.

Conventional Construction:

  • Construction takes about 6-12 months or longer.
  • At the planning stage, architects and engineers draw up one overall plan to be sorted out by all the trades. Usually no detailed co-ordination planning.
  • All trades must follow in trade sequence. Drainage lines, ground slab, masonry construction, roof structure, roof tiling, etc. Cost of detailed supervision is high due to chasing up the various trade workers for scheduling.
  • Wet weather can delay the project by months.
  • The building need to be scaffold out around the perimiter, a very costly exercise.
  • More internal trades required, eg. framers and plasterers needing to work in sequence.
  • Landscaping, driveways and paving common to both methods of construction.
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