7.2 Short-span bridges on private land

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Legally required professional: Chartered Professional Engineer

Short-span bridges (span means the actual total length of deck does not exceed six metres) could have various applications. Short-span bridges are constructed above a stream or river’s normal flow-level.

What the law says

Schedule 1 of the Building Act 2004

Exemption 47. Short-span bridges on private land

1. Building work in connection with a bridge that—

(a). has a span of less than 6 metres; and

(b). does not span a road, a railway, or any other area with public access; and

(c). is not used by the general public; and

(d). has a safety barrier.

2. However, subclause (1) does not apply to a bridge from which it is possible to fall further than 3 metres even if it collapses.

How it works

The falling height in this exemption is a vertical distance from the ground which should be measured from the lowest point of the river-bed, stream or creek to the top level of the bridge deck. Furthermore, the span is the actual distance between the vertical supports (abutments) of a bridge which are anchored into the river bank. If the short-span bridge has multiple piers or spans, the total length of deck must not exceed 6 metres.

The intended usage of a bridge can cover various cases such as medium-sized vehicles and farm trucks. In farms and private properties, short-span bridges are sometimes designed to pass over a stream or river. Some farmers might use the short-span bridges to facilitate their farm-related operational activities.

Under this exemption, short-span bridges must not be used by a member of public.

Engineering knowledge is needed to consider the loading conditions, ground conditions and to make the appropriate classification based on the loads and frequency of use the bridge is likely to encounter during its life span (such as light-duty vs heavy-duty). 

For this exemption to apply, an owner must engage a Chartered Professional Engineer (like a structural and geotechnical engineer) to design the short-span bridge and the building work must be carried out in accordance with that design.

Find an engineer — engineeringnz.org

Resource consents may be required for short-span bridges location on farms. Most short-span bridges will be anchored to the bank of the stream or river, as they need to comply with council plans (administered by city, district and/or regional councils) under the Resource Management Act (RMA).

Weight and/or speed limit signs should be fixed to the short-span bridges. Appropriate signs will help to warn other users of the bridge of its limits, including employees or emergency responders, and may to an extent limit landowner liability in the event a short-span bridge is overloaded. Installing the appropriate signs generally limits the liability of local authorities for issues resulting from the overloading of short-span bridges on private land, it could also warn other users of short-span bridges such as firefighters or employees.

It should be emphasised that having this exemption for certain size of bridges doesn't prevent the councils from exercising their power to give discretionary exemptions under the Building Act 2004.

Discretionary exemptions by councils are covered in Exemption 2 of Part 1 of Schedule 1 of the Building Act 2004 — legislation.govt.nz

What is exempt

1. A farm owner wants to build a short-span bridge over a small creek on their land with a clear span of 5 metres between supports and a fall height not exceeding 2 metres. The bridge design is undertaken by an engineer (structural and geotechnical) and the bridge has capacity signage along with a Building Code compliant barrier. The bridge will only be used by small trucks or small agricultural machinery owned and operated by the farm owner.
2. Access to a private urban home is over a short span bridge to cross a small stream. As the bridge has a span that does not exceed 6 metres, does not cross an area with public access, has safety barriers and has a fall height of less than 3 metres, the bridge is exempt.

What needs consent

1. A landowner is constructing a small bridge over a river on private land where the bridge is likely to be used by the public or employees of nearby businesses. A building consent is required for this building work as it will be used by members of the public.
2. A horse breeder wants to build a small short-span bridge over a river on private land which will not be used by the public. The bridge span which is the actual total length of deck is equal to 7 metres. A building consent is required for this building work as it spans more than 6 metres.