What are the requirements for a legal tiny house trailer? How wide can a trailer house be? There are many questions when starting out your tiny house design research stage and the trailer will be one of the first aspects to understand. As the trailer is your foundations for your house it is very important to make good decisions regarding design.

The New Zealand Transport Agency (NZTA) has a set of rules that a trailer must meet to be road legal in NZ.  They have produced two fact sheets which are important to read and understand. We will summarise the information contained in these now.

• Light simple trailers - Fact sheet 13D

• Over-dimension vehicles and loads - Fact sheet 53A
  

What is a light simple trailer?

• A light simple trailer has one, two or three axles arranged close together in an axle set.

• The maximum width 2.55m, length 12.5m, height 4.3m

• Maximum gross vehicle mass (GVM) 3500kg.

• Plus other requirements detailed in the fact sheet.

Is it legal to have a 3.1 meter wide tiny house?

In factsheet 53A there are two groups 'Specialist oversized vehicles' and 'Standard-sized motor vehicles carrying over dimension loads' we will talk about these now. 

Specialist oversized vehicles

A specialist oversized vehicle is a piece of equipment that requires oversized dimensions (larger than standard size vehicles) to complete its function, such as a crane or harvester. So a tiny house does not fall under this category as it does not perform a specialist function in terms of ''equipment''.

Standard-sized motor vehicles carrying over dimension loads

You can have a tiny house trailer that meets the 'light simple trailer' requirements as stated above which then carries the house as an oversized load. The 2.55m light simple trailer can carry a load (or house) that is up to 3.1m wide. Though in this case the tiny house does need to be detachable from the trailer as it is considered a load. This can have some benefits as the trailer can be taken to get a warrant of fitness (WOF), used to transport another house or have repairs done. So yes you can have a trailer up to 2.55 meters wide with a house (as a load) up to 3.1 meters wide.

Can a trailer 3.1 meters wide get a WOF?

We agree with what Nathan says in the video above that 3.1 meter wide trailers cannot get a warrant of fitness. As mentioned above, when it comes to over dimension vehicles/loads there are two groups; specialist over dimension vehicles and standard sized motor vehicles carrying over dimension loads. As mentioned a tiny house trailer does not perform a specialist function so therefore falls into the second group. This means the tiny house trailer must be a standard size motor vehicle which does not exceed 2.55 meters wide, but the load it carries can be up to 3.1 meters wide. There is nothing in the documentation that suggests a trailer over 2.55 meters wide can attain a warrant of fitness. 

What are the rules for a 'Simple light trailer' with over dimension load?

When travelling on the road with a tiny house that exceeds the 2.55m wide trailer it falls into what is considered 'category 1' (see fact sheet 53). The below is a summary of category 1 requirements:

1. Does not need a permit to travel.

2. Vehicle can safely complete its journey.

3. Must display hazard warning markings.

4. Restricted travel times.

5. No pilot vehicle required.

Can a tiny house be over 3.5 tonne and be road worthy as a 'Simple light trailer'?

It is possible to have trailer and load heavier than 3.5 tonne but would require a COF (certificate of fitness) like a truck for example. This could be an option for some cases but bear in mind there is a a decent cost involved in maintaining and getting COF's plus design work and auditing. This option usually does not make sense. As a simple light trailer the weight limit is 3.5 tonne maximum, so it would no longer meet regulations and not be able to travel on the road.