On this page we discuss strategies and methods to significantly reduce the overall cost of building a WikiHouse on a micro-lot. The main heuristic at play here is finding ways to either reduce or out-right eliminate labor intensive activities, while still creating a home with high structural integrity, high energy efficiency, and quality materials that provide a modest yet aesthetic living space.
Kit of Parts
The WikiHouse concept itself contributes to reducing house cost by significantly reducing labor time, skill, and tool requirements through precision. Because the structure begins with a precise digital design and precisely dimensioned CNC-milled blocks, the builder will know beforehand exact dimensions of every part of the house after it is assembled – no waiting to measure the as-built enclosure, you can confidently take measurements right from the design. As such, a ‘kit of exact fitting parts’ can be made off-site, in advance, and shipped to site once the enclosure is up to finish it out. For example:
- Windows and doors will be determined in the CAD design. They can be ordered in advance and shipped to site just after the enclosure blocks are assembled. At that point the self-build team simply screws the windows and doors into place.
- Exterior corrugated metal siding and roofing panels can be pre-ordered and cut at the manufacture’s site to exactly fit the geometry of the enclosure. Corner trims, window and door trims can be pre-cut as well, so that, once the enclosure is up, the self-build team can simply screw the panels and trims in place (over a vapor barrier like tar paper) with self-tapping screws and a battery-powered drill – no measuring, no cutting. Once installed, the metal-clad roof and exterior walls require no painting or waterproofing – and they will last for many decades. (As an example, North American Metals in Banks Oregon can extrude and cut to length corrugated metal panels, of multiple profiles, and in multiple colors and finishes, and ship them to site as a bundle.)
- Determining the layout of the foundation on the lot is easy. Hence, the routing and trenching for underground plumbing pipes and electrical conduits to the exact locations where they will breach the enclosure from the bottom is easy to determine and put in place. When floor blocks are being laid, one or more of the blocks will need to have a hole cut into them at the location so that the pipes can be stubbed out to the inside. This will be easy to determine.
Alternative Foundations
Poured concrete wall foundations are one of the most complex and labor intensive aspects of house building. You have to excavate the lot to make it level, build footer and wall forms, place rebar, pour concrete, dismantle forms, etc.. It’s not something a self-builder really wants to deal with and it’s costly to contract out. Fortunately, there are simpler, less costly alternatives, especially for small footprint, and comparatively lightweight WikiHouses. If the lot is level, then pouring discrete concrete pads to support a simple post and beam framework is a viable solution. However, if the lot terrain is challenging then the following alternatives can be considered:
Spaceframe Foundations
Spaceframe foundations, such as Multipoint Foundations, have many advantages over poured concrete foundations. Multipoint is a galvanized steel and aluminum, 3-dimensional, reinforced spaceframe that provides uniform support to any building, regardless of most soil condition or topology. It has major advantages when building on sloped land. Multipoint avoids the need for site excavation, ground levelling, and all the form work of concrete foundations. And, like WikiHouse, the Multipoint spaceframe can be assembled by a small team of lightly-skilled workers using simple tools.
Key Points:
- No heavy equipment required
- Can be assembled with simple hand tools
- Compact shipping in crates
- Installation is undertaken by local labor
- Designed as a floating slab
- Frame can be extended in any direction
In general, spaceframes are manufactured to spec for a given house’s footprint and the geometry of the terrain it will sit on. Vertical supports from spaceframe to ground can be varied in length allowing platform to contour to the shape of the terrain. Under each vertical support is placed a concrete pad or column to rest on. It can also rest on a set of ground screws. The end result is a level, rigid platform that conforms to the terrain, upon which a WikiHouse can be assembled.
A spaceframe foundation can potentially make it cost-effective to build on difficult terrain, or land that is at risk for occasional light flooding. In these cases there is likely an opportunity to purchase the land at lower cost compared to a level lot.
Spaceframe platforms, from small to large, open up more possibilities for siting WikiHouses.
Ground Screws
Ground Screws (aka micropiles) are a relatively new foundation solution. Because it is such a new technology, in the US each jurisdiction views them differently. First step is to determine if local building official accept the use of ground screws.
The self-builder, knowing the exact dimensions of the WikiHouse, can sink ground screws into the soil at positions to fasten pressure-treated 4×6″ or 4×8″ wood rails. For example, a 16′ x 24′ enclosure would have a 3 x 24′ longitudinal rails: one under each peripheral edge and one down the middle. Each rail would be supported by 4 ground screws, spaced at 8′ intervals. A 3″ diameter x 6′ long screw is a common size and may be adequate for our example 16’x24′ WikiHouse but screw determination must be made by a structural engineer who assesses all the aspects of the project, such as, house size, soil type, geographical wind/snow loads, etc. Screws can have a variety of load-bearing top interfaces. In our example, we would use a U-shaped cradle to hold the 4″x6″ pressure-treated wood rails. The top cradles can be height adjusted at installation time, making it easy to level the rails.
It is possible, depending on the soil composition, that a hand-held electric-powered driver can be used, i.e., a DIY option. But most likely you will want to sub-contract this out to a professional with a hydraulic driver on the back of a back-hoe. There is no set depth to sink a ground screw. The final appropriate depth is determined by a required amount of torque reached at a certain depth.
Detailed information about Micropiles.
American Ground Screw is one of several domestic manufacturers of ground screws.
Other Siting Options
- WikiHouse structures are relatively light-weight, so small structures could be sited on the flat roof of existing buildings. Here it would be straight-forward to anchor foundation rails to perch the structure on. Ability to build on rooftops opens up a lot of potential building space within the existing urban area.
- A WikiHouse structure could be anchored onto a trailer-bed like many tiny-houses are.
- WikiHouse shells could be used to create an indoor village within vacated big-box retail spaces.
The block construction system of a WikiHouse provides flexibility in where one can construct structures.
Interior Finish-Out
Interior Utilities Wall: In the typical case, the self-builder will contract out plumbing, electrical and HVAC work to licensed professionals. Cost savings may be achieved by concentrating plumbing pipes and an electrical panel in an interior wall module that contains bathroom hookups and fixtures on one side (e.g., toilet, sink and shower), and fixtures for the kitchen on the other side (e.g., sink). This wall may be scratch built after the enclosure is up, or pre-fabricated off-site then slid into the enclosure as a unit. The core idea here is to not run plumbing and wiring in any exterior wall where it would be more difficult to do.
Electrical Distribution: As seen in the adjacent picture electrical service is run inside metal conduits attached on the surface of the walls. This is a late stage fit-out after the interior finish panels are in place. Easy to install. WikiHouse wall-blocks also have plenums where wires can be run through the wall interiors.
Sheetrock Alternatives: Sheetrock is a labor intensive, high-skill aspect of finishing out an interior, requiring hanging, taping, mudding, texturing and painting. Like formed concrete work, it’s not something the self-builder wants to do, and it’s expensive to sub-out, so it’s a good candidate to reduce or eliminate.
Just Paint It: Consider that a WikiHouse is made from plywood. The faces of the plywood wall and roof blocks on the interior of the house provide a smooth, ready-to-go interior skin. One can simply apply a vapor-barrier paint or transparent vapor-barrier wood finish to the plywood to create a finished interior with the least amount of cost and effort. You can see the results of this approach in adjacent picture taken from the video in this news story: Australia’s First WikiHouse
Note that Oregon building code (and likely for all states) requires a flame spread index of 200 or less, and a smoke developed index of 450 or less for fire safety. 3/4″ plywood of Douglas Fir (and other wood) meets both of these requirements.
Panels: Any number of wood paneling products on the market could be used to finish out the interior. It provides a warm appealing space, as seen in the adjacent picture. Light-gauge corrugated metal panels can be appealing as well. The panels can go from floor to ceiling as shown in the adjacent picture, or used as wainscoting in the lower section of the walls. Simply screw them into the wall.
An intrinsic benefit of a WikiHouse building is that the entire surface of the exterior and interior walls is continuous wood. With conventional stud-framed walls you can only seam panels at the studs. With WikiHouse you can fasten panels anywhere on the wall face, and in any configuration you want, allowing for many creative ways to finish out the interior walls, including self-adhesive materials that can be cut with a razor knife and affixed to the wall such as heavy wall-paper.
Flooring: There are many vinyl plank flooring options on the market that look good and are easy to install. Traffic Master Grip Stick flooring is probably the easiest to install as you can cut it with a razor-knife, as opposed to, most click-type luxury vinyl plank that must be cut with power saws. GripStick wears well and looks great.
Interior Rooms: After the perimeter walls are finished on their interior side, partitioning the space into rooms can be done using WikiHouse Interior Blocks or with conventional construction methods, i.e., stud framed walls with skins (e.g., metal, wood or sheetrock panels). At this point kitchen counters and cabinets can be installed (IKEA kitchens are a good value). Then electrical conduits, outlets and switches are installed and wired into the service box.
