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Digital Design

Using 3Ds Max software, the architects produce detailed models containing every construction component, even determining the location of every screw hole.

To make sure the house is CNC-constructible, the architects design each house as an assembly of repetitive blocks, or cassettes. They have devised a simple process of modeling each block twice — once for the overall house form and again for the detail.

The overall-form blocks are copied and repeated to build the full 3D computer model, and the detailed version generates the production information. This avoids having an overly complex single model.

They have also developed a system for checking that all the blocks — the overall block model, the detailed block model, and the actual cassette — correspond correctly to each other. This virtually eliminates unforeseen problems on the construction site.

Unlike a relatively rigid production fabrication system, FACIT's system is flexible enough to accommodate virtually infinite design variations. Architect Bruce Bell explains that designing within their broad framework does not demand any compromises to constructability.

"Currently we are designing all sorts of different types of houses," Bell says. "We work within the limitations of the system; however it is very flexible due to the digital process behind it. So if we need to produce a half module, or a quarter module, or a funny-shaped module, the system allows us to easily design and produce them in a very short time."

To be able to deal with unexpected circumstances, the architects began with the desire to not be constrained by design rules or arbitrary grids. Although their system is modular, they're not constrained to a rigid module.

Part of their flexibility stems from their not seeing this (yet) as a mass production technique. So far, all the houses they've designed and are building are different from each other. Bell says: "We have developed this system to exist outside the rules of mass production where repetition and standardization are what govern the cost effectiveness."

He continues: "Currently we are not treating this any differently than any other architect-designed project. We have clients who have specific needs, sites that have planning conditions, and our idea of what good design is. The more removed from [the client] dialogue the design process becomes, the more chance there is of producing bland repetitive buildings."

Construction and Assembly

The construction system is based around the standard plywood sheet size of 4 by 8 feet (1.2 by 2.4 meters); the architects' chosen module is half the width of the sheet. Each cassette uses approximately 1.5 sheets — including front, back, and sides — and so is light enough for one person to lift.

After the sheets are cut on a CNC router, the components are assembled into the lightweight hollow cassettes like big Lego bricks. They are lifted into place on the job site then blow-filled with recycled newspaper for insulation and air tightness.

From the first meeting between architect and client to construction completion is only nine months. The cost of a 1300-square-foot (125-square-meter) house is about 18 percent less than a house of conventional construction. Because of its tightly integrated design/ construct process, FACIT is able to give homeowners a guaranteed price upfront, including professional fees.

Also, because the design and construction processes are so carefully controlled, the resulting house is high in sustainability standards. Control of the service penetrations means improved air-tightness. Insulation is twice that required by code. The materials are selected to minimize environmental impact, The plywood, for example, is certified by the Forest Stewardship Council. Cutting patterns are designed to minimize waste.   >>>

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SUBSCRIPTION SAMPLE Digital House, designed by Bell Travers Willson for efficient fabrication. Image: Bell Travers Willson Mechanical and electrical services. Image: Bell Travers Willson Component assembly. Image: Bell Travers Willson Construction sequence. Image: Bell Travers Willson Plywood being cut on a CNC router. Photo: Bell Travers Willson Assembling the pieces. Photo: Bell Travers Willson Cassettes placed on site. Photo: Bell Travers Willson Lifting a lightweight cassette into place. Photo: Bell Travers Willson   Click on thumbnail images to view full-size pictures.