Design
Guide

What types of building is WikiHouse suitable for?

WikiHouse is a highly adaptable building system. It may have the word 'house' in its name, but it can actually be used for a whole variety of building types, but there are also some building types that it is not suitable for. At least not yet.

Works well for

• Detached houses Independent structures with residential live floor loads. ‍
• Row houses In effect independent structures with a ~100mm gap in between them. Add adequate protection to prevent spread of fire between buildings, and possibly steel struts to brace the houses against each other.
• Workspaces for example offices or studios, with light live loading requirements. Structures can be disassembled and blocks re-used if commercial needs change.
• Garden studios  Skylark 200 is perfect for these micro offices, gyms, workshops etc, provided you can keep the height below any planning limits.
• Inserts  Structures building inside a larger space, including mezzanines, or buildings built within existing structures.
• Rooftop development WikiHouse is lightweight, making it perfect for rooftop buildings, but structures will need to be securely anchored down.

Works ok for

• Internal walls Internal walls can be assembled very quickly, but you'll need to make allowance for the wonkiness of existing walls, floors and ceilings.
• Extensions Much faster and easier to build than using traditional methods, but you'll need to be clever to match floor-levels and to connect to the existing building. You'll also need to have a straight and level base for the WikiHouse structure, and also carefully design the way that the extension connects to the old building.
• Temporary exhibition structures Rapid mount and demount makes it perfect for temporary structures, but the question is: what to do with the blocks afterwards? Can they be re-used instead of recycled?
• Garages Single storey only, and you'll probably want to use an insulated concrete floor.
• Cafes and retail spaces Single storey only. You'll need to make sure the floors can support additional loads.

Probably doesn't work for

• Garden sheds There are just much, much cheaper alternatives.
• Flats It has yet to be proved whether the WikiHouse system provides sufficient acoustic insulation and fire protection between floors to meet the requirements of flats.
• Buildings with shared (party) walls For the same reason.
• External alterations WikiHouse is perfectly straight. Most existing buildings are... not.
• Disaster response shelter WikiHouse is better for building high quality permanent homes than pop-up shelters. If you just need shelter quickly, there are probably cheaper solutions for this. However, if your focus is on rebuilding homes or community buildings after a disaster, WikiHouse might be a great tool, because you can focus on building local supply chains. Don't just build homes: build livelihoods.
• Sports halls For this you'll need a system that can afford larger spans.
• Industrial or heavy commercial uses Because of floor loads and vibrations.

What types of location is it suitable for?

Climate

WikiHouse is well suited to temperate climates. It can also be very easily adapted to extreme cold climates by simply adding additional insulation.

In hotter climates it is possible to use WikiHouse, but special attention must be paid to shading, ventilation and the introduction of additional thermal mass to prevent overheating (see staying cool).

If you intend to use any form of air conditioning you will need to apply a vapour barrier to the exterior of the building to prevent condensation forming inside the walls.

Weather

WikiHouse is not suited to sites with extreme wind loads. If you are building on such a site you will have to work closely with a structural engineer to optimise your design accordingly.

Materials

Needless to say, WikiHouse is only really a suitable solution where there is a reasonably cheap supply of structural plywood or OSB. We strongly recommend using materials carrying FSC Certification, or another certification that is equivalent or more stringent, to ensure that the wood has been sustainably sourced.

Economy

WikiHouse is especially useful in regions where there is a shortage of skilled construction workers or where construction overheads are very high. This becomes especially true in isolated contexts such as remote islands with a small population. In these areas, workers can be brought in for rapid installation, local workers used, or structures can be self-built by the local community.

In areas where skilled labour is relatively cheap but material costs are high, WikiHouse is unlikely to be cost-competitive.

Topography & flooding

Because it is usually built off the ground, WikiHouse is suitable for sloping sites (Foundations can be elevated or stepped if appropriate) or sites where it is important to avoid hard ground surfaces.

WikiHouse is not suitable for structures that would be wholly or partially underground. It is also not suitable for sites likely to flood up to a level where the timber chassis itself would be in the water.

Site constraints

WikiHouse Skylark is extremely useful for small, constrained sites or sites with difficult access. Its ability to adapt its appearance also makes it useful for sites with tight aesthetic constraints.

However, it may not be suitable if, in order to maximise your use of the site, you would need to create a tapered (or angled) building footprint (see Form).

Height

WikiHouse is intended for buildings of up to 3 storeys. This covers 95% of all buildings, and allows gentle density neighbourhoods of up to around 75 dwellings per hectare.

The main constraint on height is not gravity, but wind. In high winds, lightweight structures are more prone to slight lateral flexing, which is not allowed within most building codes. Further structural research and testing is ongoing.

1 storeys

Skylark is suitable for most single storey structures on most sites, provided your design has enough lateral bracing (see Layout).

2 storeys

On less windy sites, 2 storeys may be possible, provided your design is sufficiently wide, and has enough lateral bracing (see Layout).

3 storeys

Unless it is part of a row of houses that are bracing each other, we would not recommend using Skylark for a 3 storey building yet.

Form

For now, WikiHouse Skylark only allows orthogonal plan forms consisting of straight edges. The reason for this is simple: 3-axis CNC machines cut at 90°. The system doesn't currently allow for curved forms, or angular plan layouts (although these could be explored in future, and there are a number of ways of achieving the same effect).

Roof shape

Skylark is a flexible kit of parts but currently limited to certain building forms and compositions. As the block library grows, more roof types will be added to this list. If you feel a particular type of block is missing from the library, you can help by developing it and sharing it with us.

Skylark currently supports the following roof types:

Flat roof

The open secret of flat roofs is that they're not actually entirely flat. Skylark flat roof blocks have a pre-engineered 1:80 slope to allow rainwater to run off to a drainage channel or gutter on one side.

Flat roofs have the additional advantage of being easy to access during assembly and maintenance.

Parapet roof

Another simple option is to use the floor beams as roof beams, creating an entirely flat roof deck. This might be handy if you intend to make the roof accessible as a terrace, locate freestanding solar panels up there, or possibly add another storey at a later date. If this is the case you will need to carefully consider rainwater drainage and waterproofing details (such as gutters, scuppers or hoppers). You may also want to apply tapered roof insulation and/or a roof deck structure to allow water to run-off.

We like parapet roofs because they look good, drain well and are much easier to access during assembly and maintenance, saving on scaffolding costs.

Sloping roof

A sloping roof is a good option if you looking to use traditional roofing materials and create some additional internal height. These come pre-engineered with a 10 degree pitch, so they work with standard wall block heights. (using 2.4m (M) wall blocks on one side and 3m (XL) wall blocks on another)

Gable roof

For a more traditional gable roof form, gable roof blocks are currently available for a medium (4.8m) internal span with a 42 degrees pitch. For assembly purposes, each section of roof is made from two identical parts, which can be temporarily fastened at the apex, and lifted upwards from within the building (see the general assembly guide).

The gable roof requires the addition of a ridge beam or steel ties (to stop the walls wanting to splay outwards).

Space grid

If you're using 3D models of Skylark blocks to design your chassis, you'll find this bit out anyway, but here's a quick overview.

Skylark wall blocks create internal spaces that follow a grid of 600mm x 600mm (0.6m x 0.6m) in plan.

Main walls will then add a 318mm perimeter around this.

Vertically, wall heights increase in increments of 300mm.

Of course, if you want to make a building with a specific dimension that doesn't quite fit this grid, you can do so by making one row of smaller custom blocks.

Layout

The layout of your building is driven by two things. The first is the spaces you want to create for the occupants of the building –– we'll leave that bit up to you, although here are some resources you might find useful:

• Our Place Design Principles
• Our Generous Homes Checklist
• A Pattern Language by Christopher Alexander.

The second, which we will focus on here, is the structural capacity of the building.

With Skylark, the main structural constraint is not gravity, but wind. In high winds, lightweight structures are more prone to slight lateral flexing, which is not allowed within most building codes, because it could lead to issues like cracking windows or internal finishes. We are doing more structural research and testing to give designers more flexibility, but for now, here are some rough rules of thumb you can use.

Spans

Skylark floor and roof blocks currently range in span from Small (3.6m), Medium (4.8m) to Extra Large (5.4m). These blocks need to rest onto wall blocks at each end.

For now, these spans form the entire width of the building in one direction, although future versions will allow buildings to have any number of spans.

In the other direction, the building can be any length you like, however you will need bracing walls at regular intervals.

Window & door openings

Skylark includes a number of blocks with window and door openings. These blocks range in size from Small (0.6m), Medium (1.2m), Large (1.8m) to Extra Large (2.4m).

Bearing walls

A 'bearing wall' is any wall that has the vertical load of a floor or roof resting onto it.

In a bearing wall, you will generally need to have at least one solid wall block between any two window or door blocks.

End walls

End walls are the walls that don't have the end of a floor or roof block resting onto them.

From a vertical load perspective, end walls can have any number of openings anywhere. However, end walls will probably be bracing your structure, so this will constrain the openings you can have (see below)

Internal walls

'Internal walls' (also referred to as partition walls) are (usually thinner) walls fixed into the inside of the building. These walls should not take any vertical loads, but they may be needed to help brace the structure, and this will constrain the openings you can have in them.

If they are not needed to help brace the structure, internal walls can be added or removed during the life of the building.

If an internal wall is being used as bracing wall, we recommend putting a warning label into or onto the wall itself, so future occupiers don't tear it out without consulting an engineer.

Making sure that your walls work together to brace your building

The hardest challenge when designing with Skylark is bracing your structure against lateral flexing under high wind loads.

Any of the wall types can be used as a bracing (or 'shear') wall.

As a general rule, you should have a bracing wall every 4.8m, if possible.

The problem is, putting window and door openings into a wall will significantly reduce its ability to act as a bracing wall. Oddly enough, in testing, it turns out that bearing walls make the best bracing walls, so they are often the best walls for putting openings into. The length of a wall, and where you position openings in it has a big impact on its ability to act as a bracing wall.

Relative performance of bracing walls

Putting openings into a bracing wall will weaken its ability to resist lateral wind loads. However, in testing we have found that applying a vertical load onto a bracing wall (such as the weight of a roof, or an upper storey with a roof) significantly improves its performance.

As a rough guide, below you can see the relative performance of some different bracing wall designs. A plain bracing wall (no openings and no vertical loads onto it) is used as the benchmark (100%) to compare the others to.

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No openings

‍No vertical load 100%

Roof load 128%

Upper storey + roof load 155%

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One door to the side

‍No vertical load 50%

Roof load 85%

Upper storey + roof load 119%

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One door in the centre

‍No vertical load 47%

Roof load 90%

Upper storey + roof load 133%

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Two windows

‍No vertical load 27%

Roof load 60%

Upper storey + roof load 92%

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One door and one window

‍No vertical load 24%

Roof load 43%

Upper storey + roof load 62%

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Floors and roofs

Floors and roofs also help provide lateral stability to the structure, ensuring the whole structure behaves as one strong, interlocked box.

Therefore, try to avoid placing lots of rooflights in a row. If your design includes any double-height void spaces inside, try to avoid locating these near the ends of the building, if possible.

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Of course, none of these are hard and fast rules. Always get a structural engineer to check your project. But hopefully, by understanding and using the basic principles, you will be more likely to arrive at a design that can be approved first time, saving you money on engineers' fees.

Foundations

Skylark can be used with any type of foundation, depending on your site and needs. The most important thing to remember is that with Skylark, foundations serve to hold the building down, as well as up.

The rails

The Skylark chassis always fixes down onto treated timber 'rails' that must be bolted to the footings below. These rails must follow the line of all perimeter walls, located to within +/- 5mm of their intended position, and perfectly level.

The chassis will then need to be bolted or screwed onto these rails using steel I plates or L plates, that fix the rail to the Skylark 'combs'. These plates will usually need to be located at least every 6m, but your structural engineer will need to confirm this.

Damp-proofing

Always make sure the WikiHouse chassis is well clear of the ground. You should also always use a DPM (Damp Proof Membrane) to prevent moisture transfer into the timber rail. This might include a DPM that wraps upwards to protect the bottom edge of the chassis from rainwater splashing back up from the ground.

Foundation types

What type of foundations your rails are mounted onto is up to you.

Helical screw piles We love these because they can be rapidly installed, reused and have a much lower carbon footprint than concrete, but they might be slightly more expensive than other options. You will probably want to use stone blinding on the ground below, and anti rodent mesh.

Make sure there is at least 150mm between the underside of the building and the ground to allow for drainage and ventilation.

Trench foundations Make sure the concrete includes sufficient holes to allow sufficient cross ventilation of the cavity beneath the building. You may also wish to use rodent mesh and stone blinding.

Make sure the ground below the building is well drained and that there is at least 150mm between the underside of the building and the ground to allow ventilation.

Raft / slab foundations In cases where you want your ground floor to take heavier live loads (eg a garage for vehicles) or have a greater thermal mass, or where height is at a premium, you may choose to use an insulated concrete slab instead of a timber suspended ground floor. In this case, the rail is bolted to the slab and the Skylark wall blocks fixed onto it.

Sizing your foundations

The precise design and specification of your foundations will depend on two factors.

• Loads Your chassis structural engineer should provide you with a set of requirements for the upward and downward forces on your foundations, based on your design and the expected wind loads at your site.

• Ground conditions Your site will need to be assessed for geological composition, contamination and flood risk. This may be done by a geotechnical engineer or, increasingly there are foundation engineering companies who will provide a full site survey, design and install service.

Always get your foundations installed in advance

Groundworks are the most unpredictable part of any project. We strongly recommend that foundations and foundation rails are installed well in advance of the Skylark blocks arriving on site, along with any service connections.

Insulation

Skylark blocks are designed to have insulation pre-fitted in the workshop, so they arrive on site ready to be installed. However there are a few junctions between blocks where extra insulation may need to be fitted during installation.

It is essential that there are no gaps in the insulation, and no un-insulated cavities.

You may also choose to insulate internal floors, to prevent noise transmission within the building.

What type of insulation can be used?

In general, you can use almost any type of insulation, but we recommend a soft-fill insulation roll as it's easy for manufacturers to fit and won't leak out.

We love insulation made from recycled plastic, or bio-based materials made from hemp.

Insulation depth

The standard insulation depth in the walls is 250mm (in the case of Skylark 250) or 200mm (in the case of Skylark 200). In roof or floor blocks you can add more, often up to 350mm.

Usually it is not possible to buy insulation this thick, so this thickness is made up by using two layers.

Adding extra insulation

The standard wall depth offers an excellent level of energy efficiency, however it does still allow some thermal bridging through the plywood. So if you are in an extremely cold climate, you may want to add even more insulation. The best way of doing this is to apply a layer of rigid wood fibre insulation to the outside of the chassis before wrapping and cladding.

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Airtightness

Making buildings airtight is key to keeping them energy efficient. If you are attempting to reach PassivHaus standard you will need to reduce air leakage to 0.6 ACH (Air changes per hour) but if you're not, 1.5 ACH a reasonable target (this is significantly better than the Building Regulations requirement; sadly most new buildings still only achieve around 4 or 5 ACH).

Making your building airtight is also important because you need to stop warm humid air from seeping through the insulation of the building, and forming condensation within the timber walls.

Making your building airtight means:

Line and tape the chassis

Apply a vapour barrier to the inside of the chassis. Although cheaper products are available, we recommend using a higher-performance product which is less prone to tearing. These products also tend to allow any moisture that may get trapped in the walls to breathe out again.

We recommend using a flexible tape, because, again it allows for some movement without splitting.

You will probably want to wrap the vapour membrane into the service zone (to allow room for services to be positioned within it) and it will need to be carefully applied behind intermediate floors, (see the General Assembly Guide), so make sure you buy enough.

or

Tape the chassis

Depending on your preferred internal finish, you can also just use tape to seal all the holes and seams in your chassis. However this may be more costly in both money and time, because the tape is quite expensive. However, on flat faces where there is unlikely to be movement it may be possible to use a less expensive tape.

Seal service penetrations

You can buy special rubber collars (or 'grommets') to ensure the building is airtight where pipes or wires enter or leave the building.

Lose the letterbox

No doors with letterboxes. Dropboxes are the future anyway. If you need to install a cat-flat or similar, find one that is as airtight as possible when closed.

Build tight, ventilate right.

With the building now airtight, it becomes necessary to properly ventilate the building so there is a constant supply of fresh air into the building and stale, humid air is removed, but without losing any of the warmth. The solution to this is to use MVHR (Mechanical Ventilation with Heat Recovery) (See Ventilation).

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Note that if you intend to use air conditioning in the building, you will need to fit a vapour barrier to the exterior of the chassis as well - to prevent warm, humid air from outside reaching the cold inside face of your wall, which could lead to condensation forming inside your wall. Make sure you specify a product that will still allow any moisture trapped within the walls to escape outwards.

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Cladding

Guess what? Yup. You can clad WikiHouse Skylark in anything you like.  This is important, because you might want to blend-in or complement the materials of surrounding buildings, or, if you're building a row of buildings, you might want to use a different material on each one, to add variety and texture.

First, wrap the chassis

Whatever you're going to use as your final cladding, the first thing you need to do is wrap your building in a breather membrane. This will keep your structure dry, whilst allowing any moisture within to breathe out - like a GoreTex jacket.

If your final cladding is going to have any gaps in it your breather membrane will need to use a UV-resistant.

If your building is going to be adjacent to another building, you may need to use fire protection, such as an intumescent (fire-resisting) membrane on end walls, and around the corners onto facades.

With that done, you have a range of options:

Bricks or brick slips

In theory, you could use a leaf of bricks or brick slips, but these can be very costly (in time, money and carbon).

Timber or shingles

The most popular options are timber rain-screens or boards. Usually this involves fixing battens onto the wrapped chassis then fastening the cladding onto those battens.

Battens can be screwed into the 18mm plywood of the chassis at any point.

There are so many possibilities for cladding types you can explore. From more traditional cladding like timber boards or wood shingles, to more contemporary materials like larch cladding, and some really beautiful innovative solutions made from recycled plastic or wood waste.

Fibre cement slates

Fibre cement slates give the same kind of beautiful, fine grain texture as bricks (they come in a range of bond-types and colours), and can provide a more robust defence against vandalism or arson than timber cladding, but they are slightly more labour intensive to install – it is more likely that fixed scaffolding will be required.

Panels

Undoubtedly the fastest and simplest cladding type is panels, such as fibre cement panels. The straightness of a manufactured chassis also makes this easier. However, unless they are textured or corrugated, panels can also make buildings look clumsy, 'prefabricated' and impersonal, if they lack the fine-grain texture that tends to make for well-loved buildings. Also, manufacturing costs can be high, if the panels cannot be cut by hand.

Pre-made timber panels

A good compromise can be to pre-make whole panels (of, for example timber) cladding in the workshop, then quickly fit these onto the building on-site, but make sure you design-in some tolerance as the real life chassis might be a few millimetres larger than your computer model.

Render

It is is also possible to apply some forms of (flexible) render onto the chassis. We are particularly interested in the possibilities of spray-on cork render, for example.

Fire protection

If you are building a row of adjacent buildings you will usually need to use an external fire barrier material, not just on the sides of the buildings facing each other, but also wrapping around the corner and onto the face of the building, to prevent fire from spreading from one building to the next.

Windows and doors

Skylark is compatible with pretty much any type of window or door. What's more, the precision and predictability of the chassis mean that the units can be ordered in advance instead of needing to be measured on-site, so your project doesn't need to be delayed for weeks while you wait for them to be made.

What type of windows?

Seriously, we mean it. You can use almost any type: fixed, sash, casement, Oriel. Wood, alumnium, uPVC. But we find that inward-opening, double-glazed tilt & turn composite windows look great and last well. Inward opening are easier to clean, allow for the use of shutters or shades, and give a strong sense of connection to the outside when open.

Double or triple glazed?

Modelling by Leeds Beckett University suggests that actually the extra cost of triple glazing (in money and carbon) wont really pay for itself over the lifetime of a WikiHouse. Good quality, durable double-glazed windows are probably where it's at.

Incidentally, it is an under-acknowledged rule that if you want to make a house feel robust and expensive, spend the money on the window seals and handles. The Germans seem to know this. Angela Merkel was once asked what, for her, defines Germany as a nation. She replied

“I think of airtight windows. No other country can build such nice and airtight windows.”

Sizes

WikiHouse window blocks have standard opening sizes that should be accurate to within 2mm.

However, you may find that window manufacturers offer standard off-the-shelf sizes, and these may be considerably cheaper than having your windows custom-made. If this is the case, we recommend adapting the Skylark window blocks to create smaller openings.

Mount windows onto brackets

Whatever windows you are using, it is a good idea to mount them onto brackets, inset from the opening itself. This allows room for a bit of movement or expansion (of the building or the window), without distorting or cracking the window. However, make sure that the bracket is only connected to the 'warm' part of the window frame, otherwise the chilled metal will collect condensation.

Seals and finishes

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, expanding seals or silicone sealant, and expanding insulation. It is impossible to overestimate the ability of cold wind or driven rain to find its way through even the tiniest gap around the edge of a window.

Skylights

All the same applies to skylights (or 'rooflights'). There are a number of  companies who will make skylights that can be directly fixed onto the face of a WikiHouse chassis, making them surprisingly easy to install.

Openable skylights can be an important part of your strategy to keep the building cool in summer, by allowing hot air to escape upwards.

Get the windows delivered before you start

We recommend getting the windows and external doors ordered, delivered and waiting (safely) on site before you start assembling the chassis. Once the structure is up, the installers will want to get it wrapped and weathertight within hours, if possible.

Roofing

WikiHouse Skylark is compatible with most types of roof materials and techniques.

First you should ensure the roof is very well wrapped in a suitable breather membrane. Then roofing material can then be applied

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Here are some of the top candidates.

• Steel standing seam Such as this product by TATA. It's robust, recyclable and relatively easy to install. Also it looks fantastic.
• Corrugated panels Utilitarian in appearance, but low cost and can look great if detailed neatly at the edges, especially if the external walls are also clad in the same material.
• Butyl rubber or EPDM membrane There are a whole range of products, including self adhesive and reinforced membranes. They are often used on shallow-pitch roofs, but they don't have to be. They can be excellent value, especially if the roof is behind a parapet or beneath a deck.‍
• Sedum / green roof Often these are laid over a butyl rubber or EPDM membrane roof. There are an increasing number of modular tray products, but make sure you carefully follow guidance around correct detailing and drainage.‍
• Tiles / slate You may want your building to blend-in to its setting by using a more traditional (albeit laborious) roofing method, mounted onto battens in the usual way.‍
• Fibre cement slates Fibre cement tiles also work well, especially if you are also using them as cladding but, like tiles and slate, they are slower to install; almost certainly requiring fixed scaffolding.

Internal walls

The straightness and accuracy of the chassis make it relatively simple to add or remove internal walls anywhere within the structure. This leaves plenty of scope to alter the internal layout of the building during its lifetime.

Internal walls can be made using WikiHouse Weaver, or conventional stud framing. Weaver has the added advantage of presenting an 18mm thick face, which should be strong enough for fixing most kitchen units, shelves etc into.

Bracing walls

If an internal wall is being used as bracing wall, we recommend putting warning labels onto the wall itself, so future occupiers don't tear it out without first consulting a structural engineer.

Acoustics

To create an internal wall with additional acoustic protection, you can fill it with acoustic insulation, face it with acoustic plasterboard, and ensure you use a sealant or tape around all edges to seal any gaps.

Stairs

Skylark stair blocks can be inserted more or less anywhere into the chassis.

Stair voids

By definition, stairs can generally only align with the direction of the floor blocks. In some cases you may need to create custom blocks to create your stair void and landing.

Support

It will need to be supported by (and fixed-into) a main wall or an internal wall on both sides, although if you wish to have one side of the stair open, this internal wall may not need to extend fully to the ceiling.

Types of stair

You can insert most types of stair, including:

• Straight
• L-shaped
• U-shaped (half-turn)
• Winders
• Ladder
• Spiral

However, if you are using a custom stair design that concentrates a significant load onto a particular part of the floor (for example, the central stem of a spiral staircase), your structural engineer may require that this is given additional support from below.

Building codes

Make sure your stair design meets building regulations. This is likely to cover not just the dimensions of the risers and goings, but also head clearance and the sizing of landings at the top and bottom of the flight.

Other things to consider

• Position lighting (or skylights) such that it ensures stairs are well lit, creating clear visual contrast between riser and tread.
• Bannisters that are compatible with toddler gates, which might be located at either the top or bottom of a flight.
• Opportunities to use half landings as window seats or useful spaces in their own right.
• Below-stair storage.

Ventilation

With the envelope built to such a high level of airtightness, there are two forms of ventilation to consider.

Natural ventilation

Wherever possible, design your layout to allow maximum opportunities for air to cycle around the property. This includes:

• Cross ventilation
• Use of skylights to allow warm air to escape
• Including more than one window in a room.
• Fully openable windows or doors (especially on the side most likely to receive sun in summer, but also onto the coolest outdoor area)

Mechanical Ventilation

We strongly recommend the use of Mechanical Ventilation with Heat Recovery (MVHR) to ensure homes are properly ventilated, so stale, humid air is replaced with fresh air, whilst conserving warmth in winter months. Even with small garden studios, you can buy small single-room units. With most homes you will install a central MVHR units, and run ducts throughout the home.

All Skylark 250 floor and roof blocks include ⌀130mm holes for ventilation ducts, and access holes in the underside of the blocks to allow you to reach through to install those ducts.

Designing for MVHR

Your MVHR system engineer or manufacturer will be able to provide more information about the correct size and layouts for your project. However, here are some high level things to consider:

• Air inlets are usually located in rooms such as living rooms and bedrooms.
• Air extracts are usually located in WCs, bathrooms and kitchens.
• Kitchen / dining If you layout includes an open plan kitchen, ensure there is a powerful extractor hood connected to the system, not just one that recycles air.
• Locate your external air intake carefully For example, away and upwind from the outlet, and not in an area where there are likely to be vehicle exhaust fumes or other smells or air pollutants.
• Full summer bypass Always specify an MVHR unit with a 'Full summer bypass' mode. This allows you to use it to flush the building with cool air at night during the summer (See Staying cool).
• Access You will need access to install, repair and change the filters on your MVHR unit. Locate it in a large, accessible loft space or cupboard. If the property will be rented out, you may wish to consider locating it in a service cupboard which is accessible without having to gain access to the property.

Services

Skylark wall blocks have a 32mm service zone for running pipes and wires. Under ceilings, this increases to 70mm.

It is then very easy to cut small holes through blocks and internal walls to install services, and provided these are small, occasional and spaced far enough apart they should have no impact on structural performance.

As with everything else, Skylark seeks to be agnostic when it comes to what types of services you use, however in general:

Electric-only

With such high levels of insulation, coupled with MVHR, it becomes economical to move to electric-only services (ie. no gas). Not only is this better for the planet, it also removes a whole trade (and source of delays) during installation and a safety hazard during the lifetime of the building.

Heating methods

There are several technologies you might consider:

• ‍Air source heat pumps This will require the careful positioning of a pump unit outside the building.

• ‍Electric underfloor heating Whilst not the most economical solution in terms of running costs, these are relatively inexpensive, very easy to install, lovely to use and (if your building's design benefits from reasonable passive solar gain) may only be required a few days per year anyway.‍

• Infrared radiant panel heaters These are probably the most effective in terms of both price, operating cost and access. They do have a more visible presence in the space, but you can get some very elegant, plain ones that blend beautifully into a room.‍

• Electric stoves We all love a crackling wood-burning stove, but if you were to install one in a WikiHouse, the building would probably overheat pretty quickly. But if you want one as a focal point for a room, you can get (very convincing) electric ones.

Going solar

If you can afford it, and have space on the roof, you can complement any of these strategies with solar photovoltaics or solar thermal panels. If you can't afford the upfront cost of these straight away, but think you might want to install them later, you might consider creating ducts ready to receive the wires or pipes in future, and specify, for example, a water heater that is compatible with these.

Sensors

If you can, install sensors into the building that measure internal and external, temperature, humidity, air pollution, carbon dioxide and electricity usage. If you're willing to share this data with us and/or the WikiHouse R&D community, it will be invaluable in understanding how the systems performs IRL, and how we can improve it.

The future of services

We think the future of services will include plug-and-play kits that can be installed by anyone, and then checked and certified post-installation. However, we are not aware of any such system currently available in the UK. If you know of one, please let us know.

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Read the research and analysis done by Leeds Beckett University on Energy and Carbon for homes using WikiHouse.

Internal finishes

There are three main ways you can finish the interior of WikiHouse Skylark.

Plasterboard (or 'drywall')

The most conventional approach is to fix plasterboard panels onto the chassis. These serve the dual purpose both of providing the requisite fire protection and adding some additional thermal mass to the space.

Use tapered-edge panels that are 1200mm wide, as these will align with the protruding 'ribs' of the structure.

Because the chassis is so straight, no skim is required. Mesh tape and fill is fine. You can engage a contractor to do this, or just do it yourself.

Wood panelling

When they see the raw WikiHouse chassis, lots of people want to just keep it like that, beautiful bare wood. Unfortunately, it has to be covered up in order to make the building fully airtight, and building regulations require that walls and ceilings have some fire resistance. However, there is the option of re-lining the interior with, for example, 6mm, fire-treated birch plywood instead of plasterboard.

Exposed ribs

Another possible option would be to leave the ribs of the Skylark structure exposed, and infill between them with panels of plywood or other materials such as textiles or hemp. This could be rather beautiful, and afford softer acoustics, however it does have some challenges which would need to be overcome:

• Taping All holes and seams will need to be taped to make the structure airtight, which will use more tape overall.
• Services Will have to be placed behind the panels, or surface-mounted within steel conduit.
• Fire treatment To meet building regulations, the ribs and infill panels may need to be treated to make them fire resistant.

For now, this pattern is probably only suitable for piloting on garden studios or other small structures that do not need to meet building regulations. If you use this pattern, please let us know.

Staying cool

One of the side-effects of lightweight timber buildings is that they have less thermal mass. That's to say; they take less time to heat up and cool down. In winter this is no problem – in fact it can even be an advantage. But in hot weather it can be a disadvantage. Keeping the heat in is easy, but in summer we need to get rid of it.

Fortunately, there are a few ways to overcome this disadvantage, without resorting to air conditioning:

Add mass

The most obvious move is to re-introduce more thermal mass if possible.

• ‍Phase change plasterboard There are new plasterboard products that claim to punch above their weight when it comes to thermal mass. These can be used on the walls, or even laid beneath floor finishes.

• Other mass There may be other opportunities to introduce mass (such as ceramic floors, blocks of concrete, hempcrete, or perhaps even water containers into the space or building fabric (for example into the service cavity within the walls) but you will need your structural engineer to approve this.

• Ground-coupled heat pump A high budget option. Some ground source heat pumps have a passive cooling module that as well as extracting warmth from the ground in winter, can also dissipate heat into the ground in summer.

Stop the space getting hot

In summer, the first challenge is to stop the space getting hot in the first place, if possible.

• Reflect energy Make your roof white or bare metal to reflect solar radiation

• Use climbing plants and green roofs to keep the outer surface of the building shaded and cool.

• Use your roofing or cladding as shading by having a ventilated cavity behind the outer surface of the building, so even though the outer material may get hot, that heat can dissipate. This will combine well with

• Use a reflective breather membrane to reflect radiant heat from the building fabric.

• Low energy appliances Only use LED bulbs and low energy appliances within the building.

• Get the glazing area right Most heat gain is passive solar gain through glazed windows. Of course, in winter this is a good thing, and we want homes that are filled with daylight. But in summer, too much glass becomes a problem. This is one of the reasons why Skylark window openings are, in general, narrow and high.

Shading

The most effective protection from overheating is to stop direct sun hitting the glazing during hot days.

• Fixed shades Fixed louvres or brise-soleils that block early summer morning and high midday sun, but not low sun during the winter. The problem with these, frankly, is that they can also block daylight and can look incredibly ugly and overscaled on domestic buildings. But they can be great for, for example, community spaces or classrooms.
• External shutters The southern Europeans really were onto something when they put openable shutters onto windows. Combined with inward opening windows they also allow windows to be left fully open when the occupants go out, allowing the building to ventilate but remain secure.
• Awnings and shades A simple, low-cost solution is to include deployable awnings or anchor points for clip-on canvas shades. These also have the additional benefit of offering shade to a deck or patio area, helping to keep the ground surfaces around the base of the building cool.
• Plant trees Use deciduous trees or vines near the base of the building to create cool, shaded areas of ground around the building in summer, while letting sun through in winter.
• Open water If possible, include areas of open or moving water near the base of the building. Due to the thermal mass of the water, and the effect of evaporative cooling, this will keep the air around the base of the building cooler.

Ventilation

The next tool is ventilation: letting hot air escape from the building, and pulling in fresh, cooler air, especially at night.

• Natural cross ventilation Make sure that there is a free passage of air through the house or through a room, especially at night time when the air is coolest.

• Rooflights Especially if it isn't possible to let air flow freely from one side of the building to the other (because, you know, we don't all want to sleep in the same bedroom), add openable rooflights to the roof, allowing hot air to escape upwards. Cooler air from below will be drawn-in to replace it.

• Stack effect If you're taking this principle to jedi-level environmental design you could even experiment with glazed or black-painted chimneys to the top of your building, intended to heat air up, and so create an updraft: what's called a 'stack' or 'chimney' effect. This technique only works if the air you are pulling in from below is coming from – or through – a cool, shaded area with a high thermal mass, such as the space below the building. This has yet to be done with WikiHouse.

• MVHR with 'Full summer bypass' The entire point of a MVHR (Mechanical Ventilation with Heat Recovery) system is to recover the heat from outgoing air and transfer it to the incoming air. Of course, in summer, this is the last thing you want to do. So make sure the MVHR system you specify has a 'full summer bypass' mode. This is especially useful at night, allowing occupants to mechanically 'purge' the building with cool, night-time air, so the building is nice and cool again by the next morning.

⚠︎ Some MVHR systems will cheekily describe themselves as having a 'summer bypass' mode. This is not always the same as 'full summer bypass' mode. Make sure you look for the word 'full'.

Many of these tactics – both low and high-tech – will only work if the occupants know the basic principles. For example, if at the hottest point of the day, there is no air anywhere outside the building that is cooler than the air inside, even ventilation is not your friend. In fact, at that point, your best option may be to close the windows entirely.

Landscaping

The key to creating beautiful places is often less the buildings themselves, and more the spaces between the buildings. We have included some suggestions in our Place Design Principles, but here are some technical aspects worth considering when using WikiHouse:

Levelling-up

Most WikiHouse chassis are built above the ground, with a suspended ground floor. Typically, your ground floor will be at least 380mm above the level of the ground. This has several advantages, but it also creates two problems.

• The building can appear disconnected from its context, like a box that has been parachuted onto the site, rather than bedded into it.
• It makes accessing the building harder for example, in most cases you will want to provide level-access to the building.

There are a few ways to solve both these issues.

Decks

Adding a deck moves the step-down away from the building. The edge of the deck can then become a nice place to sit and enjoy the landscape, or buys you enough space to mediate the level change, either with a ramp, or by connecting to higher ground.

Boardwalks

On larger sites, often you can create long boardwalks across a natural meadow or open water, which mediates the level change while creating an incredible sense of arrival. Make sure your boardwalk is well-lit at night.

Mini retaining walls

Another solution is to build up (or dig down), so the house effectively sits in a recessed pit below the ground level. However, it is essential that this pit does not flood, is well drained and well ventilated. You will probably want to fit a grille across the gap to prevent objects or rodents from getting into the gap.

You may wish to add additional weatherproofing to the chassis or cladding, because raindrops will bounce higher up the building's façade.

Raised beds

At points where no access is required, another trick is to create raised planting beds in front of the building. This creates an attractive green buffer, and affords somewhere to sit. By using, for example, recycled railway sleepers, bricks or wire mesh gabions, it can also add some material variety to the site, and make use of old masonry that would otherwise go to landfill.

Ramps

Ramps that stick out from the ground generally look ugly and feel terrible to use. So, where possible, place it down the side of the building, a low retaining wall or a raised planter. That way, it just feels like part of the landscape, and you can use it without even really noticing that you are doing so. Make sure your external ramp is sufficiently wide, and has a gradient that works for wheelchair users. Part M of the building regulations in England, for example, includes clear guidelines about this.

Secondary structures

Another good way to nest a building into its context (and to create beautiful spaces around it) is to add secondary structures such as walls that connect the buildings, bin stores, storage benches, bike stores, heat pump shelters, or even porches or verandahs. Even though in some cases these may physically connect with the building (or at least appear to), they can easily be built using more basic, traditional methods, such as bricks, treated timber, glasshouse kits, or even steel key-clamp. These structures can often be added after the main building is complete, and more slowly.

Raised planters from offcuts

WikiHouse parts are cut from 2440mm x 1220mm sheets of plywood. What's left behind is a thin frame. Usually manufacturers arrange for these to be chipped up and recycled, or used as fuel. However, one idea that has been suggested is to retain these and stack them up, to create earth-filled planters, treating them with a non-toxic, environmentally-safe wood protection (so they at least last a few years). No one has tried this yet: but if you do, please send us a photograph.

Help improve this guide

If spot any problems with this guide, or you have an idea for how to improve it, please let us know.