External envelope

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External insulation

If you need to achieve U-values greater than 0.15 W/m2K, then we recommend adding an additional layer of woodfibre board insulation (between 40-60mm depending on desired thermal values). This can simply be mounted directly on to the WikiHouse chassis while following the insulation manufacturers guidelines on fixings and locations.

Damp proofing

The same as with any typical timber building, adequate damp-proofing will be needed at ground level to stop moisture from the ground getting into your building. We already know we have to lift the WikiHouse structure and any timber sole plates up and out the ground by at least 150mm. Damp proofing will need to be installed below the WikiHouse frame and integrated into your substructure design. 

Make sure to install waterproofing membranes as per the manufacturer’s guidance. Specify, where possible, one company’s product suite, getting their specification advice ahead of time. Check for a system warranty, rather than a product warranty. That way, if there are any issues with the performance of the waterproofing products, it can be clearly addressed by the manufacturer/installer. 

The damp proof layer should lap up and over some of your breather membrane, ensuring there is a continuous waterproofing layer.

Breather membrane

As soon as possible after you have assembled the chassis you should wrap it in a breather membrane. It should be installed on the external side of the WikiHouse walls, between the chassis and the exterior cladding. This keeps the structure dry, whilst allowing any trapped moisture to evaporate.

If the rainscreen cladding you are going to use has gaps in it, you will need to use a good quality UV resistant breather membrane. Follow the product installation guidance for details on lapping and fixing the wrap correctly.

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Roof waterproofing

Single ply membranes can work well for both the flat roof and pitched roof designed as they can be simply laid over the chassis.

A cold liquid applied membrane may also work well for roof terrace waterproofing, but it can be more expensive and messy to install.

Waterproofing layers must be installed correctly as per the manufacturer’s instructions. It is also worth checking that the roof finish you want will work with the waterproofing product you’ve chosen. Some finishes manufacturers may recommend you use their own waterproof membrane as part of their cladding system; this is often the case with green roofs and materials like standing seam.

The roof waterproofing layer needs to adequately lap over the breather membrane to ensure there is a continuous waterproofing layer.

Roofing

You can use more or less any kind of roofing, including tiles, corrugated panels, membranes or sedum green roofs. The specification is usually down to the client or architect’s selection. A classic choice is standing-seam steel, which is robust, recyclable, and relatively easy to install.

Windows and doors

The WikiHouse chassis is compatible with more or less any type of window, and the precision of the chassis means that units can be ordered in advance, instead of needing to be measured on site. We find that inward-opening, double-glazed composite windows look great. It's a good idea to mount these onto cranked brackets on the top and sides.

The most important thing is to make sure any gap between the unit and the opening is fully insulated, and fully protected from wind-driven rain using suitable flashings, tape and expanding insulation.

External finishes

The WikiHouse chassis supports most cladding types, including rainscreen cladding such as timber boards or render. In the case of rainscreen cladding, timber battens can be easily fixed anywhere on the outside of the chassis