Building consents for unusual structures

This Issue This is a part of the Building controls feature

By - , Build 122

A Mongolian ger may not be your next project, but it’s a good example of the process required to find out whether an unusual structure will meet New Zealand Building Code performance requirements.

Several Mongolian gers have been built in New Zealand. (Photo courtesy of Jaia Tipis.)
Several Mongolian gers have been built in New Zealand. (Photo courtesy of Jaia Tipis.)
Inside a ger. (Photo courtesy of Jaia Tipis.)

The Building Act defines a building as ‘a temporary or permanent movable or immovable structure (including a structure intended for occupation by people, animals, machinery, or chattels)’. It gives examples of things we may not have thought of as buildings, like a vehicle that is not movable (and occupied by people on a long-term basis) and a mast or pole over 7 m high. So can a Mongolian ger (or Central Asian yurt) be consented for use in New Zealand as a habitable building?

Building consent exemptions

All building work has to comply with the Building Code, whether the construction requires a building consent or not. Schedule 1 of the Act defines which building work doesn’t need a building consent. It includes repairs and maintenance, internal alterations to doors and the like, changes to the sanitary system, construction of retaining walls less than 1.5 m high and the construction and alteration or removal of tents or marquees less than 100 m2 to be used privately for less than 1 month.

There is nothing that would give a ger an exemption, so as a habitable building, a ger will need to be shown to meet Code requirements and issued a building consent once compliance is proven to the Building Consent Authority.

Clauses and possible solutions

Each Code clause has an objective, a functional requirement and a performance component. The challenge is to demonstrate how the ger will meet the performance requirements, as no Acceptable Solutions include them.

Fortunately, not all 35 clauses will apply to your ger application, so we look only at the relevant ones.

B1 STRUCTURE

The crux of this requirement is that the ger should have a low probability of falling down and harming anyone or anything during its lifetime. Consider all loadings that might be applied to it, including snow, wind or earthquake. With an engineer’s opinion, this shouldn’t be hard to comply with.

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B2 DURABILITY

Most people assume that this clause calls for a minimum life of not less than 50 years for all structural and difficult-to-replace components, but an important rider to the clause notes that the element’s life must be the lesser of the ‘specified intended life’ if stated, or the not less than 50 years requirement.

This gives the option of stating a lesser period of intended life (perhaps 10 or 15 years) and then providing evidence that the ger can meet that. A new permission to use would need to be obtained at the end of the period if the ger was to continue to be used.

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C FIRE SAFETY

This clause has four components and is only relevant if the ger is built close to a boundary:

  • C1 Outbreak of fire – relates to fire appliances and would be no more restrictive to comply with than any other type of construction.
  • C2 Means of escape – the ger would need fire resistant external walls if it is nearer to the boundary than 1 m.
  • C3 Spread of fire – a ger should comply, as a detached dwelling (category SH) is permitted to have just one exit.
  • C4 Structural stability during fire – ensuring that occupants are able to evacuate during a fire without being put at added risk. The Acceptable Solution has nine parts but most apply to larger more complex constructions than a ger.

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D1 ACCESS ROUTES

A ger would comply with this clause if there is safe access into and out of the construction.

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E1 SURFACE WATER

This clause covers outside water and how to manage it so no harm comes to the occupants of the dwelling. Much of it relates to getting surface water away. It does mean that particular care needs to be taken so surface water doesn’t get into the ger or onto neighbouring properties, even during extreme weather.

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E2 EXTERNAL MOISTURE

Because there is no Acceptable Solution that covers construction even remotely similar to a ger, it is important to understand the clause completely. The objective is ‘to safeguard people from illness or injury that could result from external moisture entering the building’. The functional requirement expands further: ‘Buildings must be constructed to provide adequate resistance to penetration by, and the accumulation of, moisture from the outside’.

So we have to keep water out, and if any does get in, it must do no harm. How to show this is one of the most difficult parts of the process. The construction method and materials to be used (with their specifications) must be incorporated in the submission, but there are no standards to compare to and no Acceptable Solutions or Verification Methods to pass.

Obtain a producer statement from the material supplier of the roof and wall materials to verify water head figures, noting their suitability for this use. As this is an alternative construction method, you need agreement from the Building Consent Authority that it will meet the performance requirements of the Building Code. Expert opinion and peer review will be the most useful tools in convincing the consenting official.

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E3 INTERNAL MOISTURE

This covers condensation management within the building and the wet areas, ensuring finishes within kitchens and bathrooms prevent moisture getting into parts of the building that must remain dry.

How difficult it is to address moist air issues will depend on the specific design and whether living activities are isolated. This will be a hard but achievable clause to comply with. Much of the design will need to be conventional and conservative.

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THE FS ARE EASY

Clauses F1 to F5 apply generally and will be straightforward to comply with. F6 Visibility in escape routes, F7 Warning systems and F8 Signs would only be relevant for a multi-unit ger.

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G1 PERSONAL HYGIENE

The functional requirement that buildings ‘shall be provided with appropriate spaces and facilities for personal hygiene’ must be considered when you are proposing using a ger as a house. The performance clause calls for ‘an adequate combination of thermal resistance, ventilation, and space temperature must be provided to all habitable spaces, bathrooms, laundries, and other spaces where moisture may be generated or may accumulate’.

The Acceptable Solution G1/AS1 has a lot of detail but will lead you towards constructing conventionally. A good option might be to have a separate ablutions area.

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G2 LAUNDERING

Under the Acceptable Solution G2/AS1, once your household unit is for more than two people, a complying facility must be provided. Clear details are provided.

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G3 FOOD PREPARATION AND PREVENTION OF CONTAMINATION

This should be an easy clause to comply with.

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G4 VENTILATION

This clause is to protect people from illness resulting from a lack of fresh air. The functional requirement calls for spaces within buildings to ‘be provided with adequate ventilation consistent with their maximum occupancy and their intended use’. A ger will be naturally air-leaky but G4/AS1 calls for opening windows or other opening areas not less than 5% of the floor area.

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G5 INTERIOR ENVIRONMENT

It would be normal for a ger to have a significant heating source. This clause relates to being able to heat the dwelling so occupants remain healthy so shouldn’t be hard to comply with.

Inside a ger. (Photo courtesy of Jaia Tipis.)

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G7 NATURAL LIGHT

The performance component of this clause is specific in calling up a light level of 30 lux for 75% of the standard year, that is, between 8 am and 5 pm each day. This should be achievable with a central roof light (the toono) and a couple of side windows.

Arrange a lux reading and provide evidence of this in the consent application.

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G8 ARTIFICIAL LIGHT

When there is not enough natural light, this clause has a safety requirement to provide 20 lux at floor level. The design needs to meet this.

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G9 ELECTRICITY, G10 PIPED SERVICES, G11 GAS AS AN ENERGY SOURCE

These clauses need to be complied with if they are being installed in the ger.

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G12 WATER SUPPLIES

This is important for all new construction. Of particular note is the performance requirement that drinking water must be potable. This will necessitate following New Zealand drinking-water standards, which means screening for particulates and treating for contaminants.

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G13 FOUL WATER

This concerns the treatment of waste and applies to all construction.

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H1 ENERGY EFFICIENCY

Whilst Mongolians live in their gers through a temperature range of 40°C to -40°C, they would struggle to meet H1 even with the ‘two fingers of felt’ that they mainly have. Our H1 requirements are now quite high, but only need to be complied with if you’re being supplied with electricity from your network utility operator. If you’re off grid and don’t use depletable resources, H1 doesn’t apply but insulation would still be very worthwhile.

However, it’s desirable that your ger is energy efficient and cosy. To find out the thermal efficiency of your ger, calculate the heat loss using the formula for the calculation method in NZS 4218:2009 Thermal insulation – Housing and small buildings. If an insulated floor is installed and insulation levels similar to conventional timber-framed construction are achieved in the walls and roof, a performance equal or better than the reference building may be achievable, although windows may make this difficult.

Design professional can help

No one said it would be easy, but the consent process for all construction is now thorough and detailed. Design professionals have adjusted to this, and successfully navigate the process on a regular basis. Using an experienced designer to facilitate a consent application is an option worth pursuing.

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Articles are correct at the time of publication but may have since become outdated.

Several Mongolian gers have been built in New Zealand. (Photo courtesy of Jaia Tipis.)
Several Mongolian gers have been built in New Zealand. (Photo courtesy of Jaia Tipis.)
Inside a ger. (Photo courtesy of Jaia Tipis.)

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