A British bespoke housing architectural firm has developed a highly innovative process linking its BIM design tools to a portable onsite computer controlled fabrication system. It is design build, but not as you know it

In this digital age of 3D modelling, and advanced manufacturing, there is huge potential for revolution in the construction process, which connects the design system to digital fabrication.

Initial design of a bespoke Facit Home: Large, south facing windows help to keep the house warm in the winter, and solar shading help to keep heat gains to a minimum in summer. The house uses natural, unfinished materials to blend in with its rural context

There has been much been written about the potential of ‘3D printing’ buildings. But the fact remains that the technology is still highly experimental and there can be longevity issues with ‘printing’ an entire single structure.

As we wait to see if 3D printing lives up to the hype, London-based Facit Homes is leading its own revolution. Its bespoke design / build service relies on a unique digital manufacturing and fabrication process (which it calls the D-Process) that is driven directly by Building Information Modelling (BIM) data. Its on-site CNC machine, housed in a shipping container, cuts raw wood panels, which are then assembled in minutes.


Bruce Bell is managing director of Facit Homes, who runs the company along with business partners Andrew Goodeve and Dominic Wilder McCausland.

Each Facit Home design is broken down into flexible, modular building blocks made from standard sheets of timber of size 2,440mm x 1,220mm

Mr Bell studied Industrial/product design, but changed to fine art while following his interest in 3D computing and imaging. After completion, he worked at Foster + Partners visualisation and then moved on to specific project teams, doing 3D modelling and design development. One project in particular, the Chesa Futura in San Moritz, which Mr Bell describes as “a big wooden bubble”, guided the development of his ideas, as it used parametric design, together with timber and digital manufacturing techniques.

Mr Bell left Foster + Partners and completed a product design MA at the Royal College of Art, where he did a lot of experimentation with digital manufacturing techniques, including rapid prototyping, CNC routing, and punch pressing 3D wire bending.

Mr Bell was amazed at how cheap it was to digitally fabricate design components and felt that there must be some way to apply these technologies to building design.

He set up a practice with two architects which started on extensions and graduated to newbuild housing. The practice designed in 3D, rendered in 3ds Max and became an early adopter of BIM tools. But ultimately these digitally defined buildings were all being made by hand, by contractors out of brick and block. To Mr Bell this digital/manual divide was ripe for modernisation.

Research and development

Having experimented with a complete digital design and fabricate process at the RCA, Mr Bell felt there was a process disconnect that could be overcome through digital manufacturing, on a small scale, on-site.

He secured funding from the London Development Agency (LDA) to set up a research project on ‘The Digital Craftsmen’ in conjunction with the RCA. The project’s aim was to evaluate the advantages of digital manufacturing technologies and methodologies on the market, from factory assembly of complete forms to looking at modularisation and modular construction.

The origins of Facit Homes comes from this research. “We found that there is very little differentiation in the construction world and architectural world between manufacturing and fabrication,” says Mr Bell. “While you can pre-fabricate something in a factory if it’s still all made by hand then it’s not really that advantageous, the construction is just being done somewhere else. For us the core issue is combining manufacturing with digital technology. It is not about pre-fabrication, on-site or off-site, that really doesn’t matter.

“For the research it was pretty obvious that CNC routing was the perfect technology for us to engage with as it was very accessible, low cost, and required no set-up. We secured a second round of funding and set about designing a modular methodology. The CNC machine and capabilities gave us our limitations, as to what materials we could use and what our maximum sheet sizes could be, which in turn defined our maximum modular size.

“This meant we fairly quickly defined what our basic building block would be. Standard sheets of timber are 2,440mm x 1,220mm (8ft x 4ft), so component face-sizes are based on either a full size sheet or a half sized sheet. Our design system is based on getting the maximum efficiency, minimum cost and waste out of the sheets, as opposed to starting out with just an architectural perspective and working towards definitions of individual components. We have to work in both directions to minimise waste and get the maximum efficiency.”

Having established the timber modular concept, the firm set about to create full-size wall and floor prototypes from these modular components, which were machined externally and assembled in-house.

The team quickly realised they would need an in-house CNC machine. Working with Mr McCausland, who Mr Bell met at the RCA and comes from the architectural interiors ‘making’ side, they bought an 8ft x 4ft machine on hire purchase (total cost around £30,000) which could be used for this and other projects, together with subcontracting to do work for other people under a company called CNC Workshop, which provides cutting services (and which has since been sold).

In 2007 the first full sized ‘proof of concept’ two storey prototype of the building system was shown at the Architecture Foundation’s premises in London.

Facit Homes’ CNC machine cuts raw wood panels onsite. Each manufactured component has a number inscribed, defining its location and type

“We got a lot of interest from other architects but nothing really came from it. Over the subsequent few years what become apparent was that it was all about linking design and manufacture and as soon as you split it out and become a timber frame company and gave it to another architect to design with, it just didn’t work. The value is in combining all elements but it took a long time to work out how we could confidently make this into a business.”

Grand design

In 2008 the team built another full-sized prototype at ‘Grand Designs Live’ over six days and again failed to get much interest and so Mr Bell carried on with his traditional architecture practice. But in 2009, he decided that he really wanted to make this digital building process work and so sold off his stake in the architecture practice and set up Facit Homes, with a view to making it a company on its own.

The first year was spent finding clients, creating designs and applying for planning permission and generally trying to convince people that this methodology was viable. This culminated in four home builds in 2011. A year which Bell describes as: “Probably the most stressful year of my life, having built nothing in January, to having four shells by May/June.”

One of these early clients featured on Channel 4’s Grand Design program (clients Celia and Diana), which was aired in 2012 and followed Facit Homes’ process of CAD design and on-site digital manufacturing, covering everything from breaking ground to all the high quality final fit and finishes.

The D-Process

Facit Homes created its own family of parts to handle standard building components, based around the size limitations of the CNC router. “In Revit we have a whole bunch of family parmetricised component categories and these are fairly generic but contain the fundamental things we need, height, size, thickness, height of holes,” says Mr Bell. “There are many bespoke details that we have to design too, which is basically like doing carpentry on a computer.”

“The parametric capabilities of Revit are absolutely essential to us, as well as providing reporting details, scheduling, quantities. We do two overlaid models, a structural detailing model with our family of components and then a standard Revit model with standard walls, sockets etc.”

A ‘secret’ process creates the end delivery in G-code, the common numerical control programming language which tells the CNC router the cutting paths. This G-code is sent to the remote site wirelessly and provides the cutting program code to produce the required components and each part is labelled with its own unique identifier and provides essential information to the constriction team on site.

Bespoke made components drop between beams for instant and easy setting out

While the architectural designs and G-code are created from Revit at the company’s London offices, all the cutting and assembling is done on site. A shipping container that houses the CNC router is sent to the site, along with the raw wooden panels. Components are made just in time for placement. Although they did have to work out how to run three-phase workshop equipment at locations where there was only single phase domestic available.

Once the sheets are cut, the panels are assembled, and rubber hammers fit the joints of plywood boxes and then a nail gun is used to pin them together. This work is relatively unskilled and components can take minutes to assemble before being taken to the structure for fitting.

The company works between a 0mm- 2mm tolerance on the panels as an interference fit is required. “Its a balance between being too tight, too loose, between the cut out parts that make each component and then the mechanical fixings between these components,” Mr Bell said. “Then, of course, you have the weather, with sun, cold and rain all having their effects of expansion and contraction. All take their toll when you are working to very tight tolerances.”

The box sections are filled with specially treated newspaper insulation and are sealed. If similar insulation levels were to be achieved through block work, with insulation and a brick skin, the walls would end up being incredibly thick and expensive.

Facit Homes also completes all the internal fixtures and fittings as well as internal and external finishes, which vary from simple render to laser cut metal louvres or cladding, depending on the client’s wishes.


Maintaining intellectual property is a key concern for Facit Homes. It initially thought to license the libraries and lease on-site CNC machines to allow other architectural firms to design houses, and send them back to Facit Homes to do the details and produce the G-code.

However, the company now appears to be favouring setting up joint partnerships as it has done in Denmark and more recently in Australia.

The company is always evaluating what new technologies have come on the market, as capabilities change every 6-12 months as performance increases.

The Facit Mobile Production Facility features a CNC machine housed in a shipping container

The core chassis of the modular system is also continually evolving with each project adding to the library of components they create. Improving buildability, weight, size, speed of assembly are key factors and after each build, adjustments are made to the components and the process.


Facit Homes’ approach to design is fundamentally based on harnessing the power of computers and specifically BIM. Through research and dogged persistence the company has connected this 3D information rich front end to a modern digital fabrication back end and come up with a system to break down buildings into flexible, modular components.

It would be wrong to consider these buildings or this approach as prefabricated. The system Facit has come up with is flexible enough to create modern contemporary homes, or replicate more traditional tastes, such as the Georgian build I visited in research for this article.

In many ways Facit Homes is an architectural firm that has reclaimed ownership of the build process, offering a reassuring single point for clients to go from art to finished home at a fixed cost.

Facit Homes’ green credentials are built into the design and are insulated above regulations, approaching Passivehaus standards. All the off cuts and timber ‘waste’, of which there is inevitably some, gets sent back to the saw mill and is used to power the factory.

The company rightly guards its intellectual property, but I cannot help wondering why others are not considering this approach. The system has many applications, producing temporary structures, houses for disaster relief or, dare I say, the timber prefab market that never really took off in this country.

Perhaps the greatest accolade I can give having seen the process and the quality of the end result, is that I definitely want Facit to build my dream home.


Bruce Bell on prefab vs digital fabrication

For a long time AEC Magazine has tracked the modernist ‘prefab’ market and seen it fail to gain any real traction, despite some fantastic designs. Most architects that venture down that route may only get as far as the design stage, some a website and a few, somewhat ironically, get to build a single example of their mass-manufacturable house. We asked Mr. Bell for his thoughts on prefab vs digital fabrication.

“From our research we found that there have been many attempts to design the ‘ultimate building system’ and that lead to standardisation, which leads to repetition, which leads to boredom and then disappointment. This is particularly true of factory production.

“There is a direct correlation between factory fabrication and repetition because you can’t have factories sitting idle due to the overheads. So as soon as you have a factory, you need turnover and in order to have turnover, you need standardisation and you end up producing the same thing over and over again.

“While if you build on-site, which the vast majority are, the constraints are completely different and has benefits such as having no heating, storage costs etc, as a factory would.

“The economics (of Prefab) just don’t stand up. It leads to standardisation and people don’t want the same, and every site has its own requirements. There is no one size fits all.

“Big home producers have tried volumetric production. There have been £60,000 house competitions, which pair up manufacturers with house builders but this doesn’t take the industry very far from where we are already.

“Maybe we are making a few more panels in a factory but then you have to get them onsite. There is no value in producing whole houses in factories with the additionally high transportation costs, which may be up to 20% of the price. Those that are doing that, like Huf House, service the higher-end of the market and are fairly inflexible. While there are options, essentially every house is the same albeit high quality, high finishes etc.

“We want to give that manufactured product quality but without the cost so let’s integrate technology and digital design into the traditional process, rather than trying to revolutionise the industry.”