Although it appears that we have been quiet, much progress has been made behind the scenes this year on putting New Zealand's first, fully-finished WikiHouse on the ground. Big steps have been made in developing the design, much prototyping and testing has been done, all while managing a shift of the WikiLab from Addington to a larger fabrication premises in Hillsborough, in SE Christchurch.
Voluminous amounts of CAD modelling have been carried out as we have continued to refine and improve the design, and we have cut two full-size portal frame sections. The assembly of these is now allowing Danny Squires to physically prototype the cladding and insulation systems at full size, to ensure our innovative environmental design ideas are realised. The full-size building pieces were cut at Inline Furniture Design in Aranui.
Structural Design Update
Thanks to the generous support of consulting engineers Powell Fenwick, one of our Wikiteers, Darren Kho, has been able to spend an average 8-12hrs a week working alongside three of their engineers. The access to peer review along with all their structural modelling software has proved invaluable in assessing the likely performance of our designs.
Martin Luff and Rachel Wood have focused on refining and testing the design iterations of the main structure. This has allowed us to undertake extensive calculations on how the structural frame stands up to both permanent and imposed loads. The permanent load is the weight of the building itself – the structure, cladding and everything else – and the imposed load is what gets added, like your grand piano in the lounge or library of books or loads during maintenance. On top of that, the other main loads are dynamic ones such as snow, wind and seismic (earthquake) loading.
Of highest concern is wind loading, which might surprise some people expecting that seismic loading would be top of the list, especially given the ferocity of some of the quakes Christchurch has recently experienced. However, on a day-to-day basis, a violent storm with loads of snow is more likely to destroy a building.
Because the planned WikiHouse is an exciting shape, with slightly sloping walls and a steep north-facing roof, we have had to do extra calculations in regard to wind loading. The steeper the roof pitch and the apex, the more there are low-pressure areas that form around the apex and the eaves. The difficulty with wind loading is that while it pushes really hard on one side of the building, there is also a corresponding negative or a lower-pressure area on the other side creating a suction (or pulling) effect on the building. Corners are critical for structural strength, and because the WikiHouse design has taken the joints away from the corners, it is crucial to determine the stresses here. We theorised that by taking the joint away from the weakest place in the building, that is, where the main wall elements meet the floor or the roof, the structure will be considerably stronger. Therefore we've designed our own system to transfer the load around those corners. This has been achieved over several iterations developed from our original initial proof of concept model, making our transfer plate different from anything we've seen anywhere else.
Other developments include working to eliminate the central supporting columns within the portal, which provides greater adaptability for internal design layouts. This makes the whole building lighter, with lower mass and less foundation requirements. Secondly, it becomes easier and safer for ordinary people to assemble the building. As the portals get lighter, they are easier to handle - it also means less cutting time (cost) and fewer materials.
Although we still have further testing to complete, the initial house could have a clear span of 6.4 metres, by far the longest span achieved by any WikiHouse design to date. This gives us a lot more flexibility in the type of space we can craft, and will be better for such uses as public buildings and schools, which require larger internal spaces.
Foundation Design Update
The second exciting thing on the structural side is that we have designed a new floor plate waffle system that utilises a two-way box beam combined with a structural plywood skin top and bottom. This will move some of the functions of the foundations up into the floor of the building, meaning the entire structure can be supported on just two ‘rails’ (bearers), whereas previously we had planned for three.
The building will be cantilevered by about a quarter of its width at either end, which will give the appearance that the building is hovering above the ground. This advance promises to reduce the overall foundation requirements, which in turn reduces the time on site, ground works and cost of the foundations.
We hope that an additional feature, of particular interest to Christchurch people, is that the very strong yet flexible floor allows us to reduce the individual load-bearing requirement for each pile. Because of its toughness, if we get any subsequent differential settling, it will automatically try to distribute the remaining mass to the piles that haven't settled – basically, it will try to self-level.
In traditional construction, you try at any cost to stop the building settling differentially, because it is likely to start falling apart. Whereas, our design is quite happy to even live without some support points for a period of time if needed until relevelling can be carried out.
We still have to make sure this all stacks up in reality, but our consultant engineers at this point are happy to support further exploring our vision for that.
Structural Testing Capability
Another exciting development is that we have begun destructive structural testing. One aspect of this is testing at scale, and for the first time we have been cutting new models at quarter and one-third scale in plywood. Previously, our scale models had always been at 1/6 scale cut from medium density fibreboard (MDF). While the models have given us very useful feedback, MDF is a completely different material from the structural grade plywood that will comprise the finished building.
We have now completed cutting several portals (frame units) at quarter scale in plywood. Using a test rig designed and built by Martin and Rachel, we have begun testing these portals. The results have shown they have failed at higher load levels than anticipated.
A full-size test rig will require up to 10 tonnes of concrete which has been kindly donated by Mark Lanyon of Lanyon & Lecompte Construction and formed into 20 half tonne blocks. Essentially, the rig will comprise two big stacks of concrete blocks, some steel beams, and a 10-tonne jack. Framing elements are anchored by the concrete, and then stressed in the middle until they break, which will tell us the load they can bear and the weakest point of the structure.
Progress at putting New Zealand's first WikiHouse on the ground currently resembles something akin to the old adage of a duck on a fast-moving stream: nothing much apparently happening on the surface, but paddling like steam underneath.
Back in April at our launch event for the first ever WikiLab in the world, we set a self imposed target that we “...will build a 25-30 square metre prototype house by the end of the year”.
Whilst we have made enormous progress this year, the impending approach of the holiday season sees the necessity to extend beyond this deadline for a fully completed demonstration model of the BackYarder™. Along the course of the year the size of the BackYarder™ has grown from 23 to 40 square metres after much consultation, and analysis of initial early adopter's feedback.
The essential reason for the stretch in the timeline is simply that when you are attempting to bring things together in a uniquely different way there is no established blueprint to follow. We are creating a new system, not just building a house (although many people would tell you this is hard enough!).
We will continue to take the time required to research deeply all the elements and develop the partnerships that are required to create a fundamentally different system - one that enables the delivery of high performance buildings by ordinary citizens having little formal skills or training in construction.
What we are attempting has never been done in this way before. Even in the UK, where the system was originally devised, current builds are a hybrid of the WikiHouse system and conventional fixed building techniques. As our two founders, Martin Luff and Danny Squires, say: It's not about building a building, it's about building an adaptable system that will eventually enable the creation of hundreds of different building types, which thus requires a longer development time than for a one-off building.
Our development progress has aimed to make the building affordable over the life cycle, more adaptable to changing needs, stronger, safer and more resilient, with healthier building materials to dramatically reduce the effects of synthetic chemical off gassing into the indoor environment. What we are doing is pushing at the edge of innovation. There are few examples where anyone has tied these things together before in the way that we are attempting to do. People are beginning to notice this, and we are receiving comments along the lines of “you've thought of everything”, although we are not letting this go to our heads as there is still much, much more to consider.
Scale test-models ultimately achieving an integrated flooring system and cutting tolerances within fractions of a millimetre.
Designing and refining the detail of every component, down to the smallest peg, has been a mammoth task. A 1:6 scale model of the BackYarder™ structural system has now been cut and assembled at our WikiLab, and this is laying the groundwork for a full production cycle.
Among the innovations, the design includes:
~ A new approach to subfloor framing with an integrated flooring system, as a way to incorporate the interface of the foundation system into the actual frame of the building.
~ Cutting tolerances to within fractions of a millimetre, which represents an extraordinary leap in precision for housing production.
~ A new approach to insulation, utilising breathable natural materials which can be easily installed and subsequently demounted, uninstalled and then reinstalled at a different location.
~ An intelligent system of exterior cladding, which will include a rigid air barrier of non-hazardous magnesium oxide panel sheathing. This will create a weathertight system with enhanced moisture management, thus addressing the issue of unhealthy building skins.
~ Solar electricity generation via integrated panels on the roof combined with appropriate shading to the house along the north facing windows to reduce summer heat gain.
~ As always, one of the driving factors is developing methods that allow ordinary, unskilled people to actively participate in the fabrication and assembly of WikiHouse structures.
The entire frame, including flooring, can be produced from sheets of plywood containing different layouts of interlocking components that minimise the need for additional mechanical fixings. A major exercise has been ‘nesting’ the components to get the best use of the sheets. This means we can now tell very precisely the amount of materials needed for the initial BackYarder™ series of the WikiHouseNZ system.
Our values of using adaptable design that empowers people to create protective environments remain the driving consideration when developing the finer details. Our openness and transparency has also been favourably commented on. This extends from the “open source” nature of the design, through to the building componentry. Our aim is that visitors to the demonstration model will be able to see how the system fits together, as well as the completed finish.
Now we have settled on a proposed internal layout of the BackYarder™, we are planning how the interior relates to the exterior with the positioning and sizes of window and door openings. The BackYarder™ requires no internal walls, as relocatable joinery units will be used to create flexible spaces. The interior will be fully fitted, including flexible plumbing and electrical positions.
At 40m² this starter BackYarder™ model forms the nucleus of a larger house.
Our design team have been constantly refining the design and testing materials since March, in preparation for erecting our first demonstration BackYarder in the fourth quarter of this year.
For the latest on the BackYarder structure development, click here.