Roofing materials for school buildings

Your project manager or designer should guide you on the best roofing material when you're getting a new building or replacing a roof. You can also get advice from your property advisor when you’re reviewing your existing roof safety.

When choosing roofing materials, you should consider:

• how the roofing will stand up to local weather conditions
• how it can keep energy costs down
• which components may have shorter lifespans – like plastic materials that may become brittle or degrade
• if it's suitable for your school’s location – for example, if your school is close to the sea, the roofing should be able to resist sea spray corrosion
• if it matches the building’s design and type of construction
• if it can improve the building’s appearance
• if the cost will be within the project budget. 

Light roofing materials reduce the risk:

• to life in a major earthquake
• of damage to the building in a moderate earthquake.

Our policy is that heavy tile roofs must be replaced with lighter materials when upgrading buildings. 

Roofing must be correctly installed. For example, the roof must:

• have the recommended roof structure
• be at the right pitch
• restrict accidental access to non-trafficable areas.

If it's not installed correctly, the manufacturer’s guarantees may be invalid.

Recently, some attention has been placed on roof safety in schools. This is now a priority 1 area for property spending. Unless specifically designed for, school roofs are to be considered non-trafficable areas and access should be restricted at all times, with the exception of authorised personnel.

Roof glazing and clerestory (vertical windows on roofs) glazing can be constructed in various forms and materials that include:

• domed roof lights
• translucent roofing
• safety glass. 

All of these sky lighting features allow natural light to illuminate internal spaces and external walkways. They  must meet the relevant building legislation at the time of installation.

We advise schools warn people of the risks of accessing roofs, and to prohibit access to only those with appropriate health and safety safeguards. Single storey buildings, particularly those with low-pitched roofs are easier to access. Wide eaves can be a useful design approach to deter easy access to roofs.

As far as practicable, we advise schools to prevent easily access to roofs and to warn people of the risks. Where possible, you should separate ancillary buildings and structures – like playgrounds – from school buildings to prevent ‘staircasing’ onto other roofs.

Check whether fire escapes from roofs are still active. If they’re no longer required, consider blocking access to them, or removing them altogether.

All schools should take note of any translucent roof items (sheet, dome, hatch or other element) and visually check their condition for signs of deterioration. Contact your property advisor if you have any concerns.

Translucent plastic sheeting is a material often used in school roofs and verandas. It includes PVC, fibreglass and polycarbonate roofing products. However, you must treat this sheeting as a potential danger because of the risks that: 

• people may fall through it – a risk that increases as the sheeting ages and becomes brittle
• it may catch fire as it can be flammable.

It's good practice to take measures to stop people from climbing on the sheeting. For example, don’t have any structures close by that can be climbed easily.  

Installing translucent plastic sheeting  

To manage the risks of installing plastic sheeting, we have some specific installation requirements that you must follow. Make sure your suppliers and installers are aware of them too.

Fire group classification

The Building Code requirements for internal surface finishes are given as group numbers (Clause 3.4(a) of the Code). This may be known as the ‘Fire group classification’. It represents the measure of how much smoke a material gives off when it burns. It's important that products used inside don't exceed these limits because the amount of smoke affects how easily people can escape.

There are no Fire Group Classification requirements for products used outside because the smoke can disperse.

Achieving NZBC Group Numbers for surface finishes from tests to overseas standardsopen_in_new

Installation requirements

Safety netting or mesh

Some translucent sheet materials are classified as ‘trafficable’. You don’t need safety netting when using these products – netting can be unsightly, deteriorate if unwashed and may be distorted through vandalism.  

To qualify as trafficable the material must:

• comply with plastic roof and wall cladding material standards
• have a UV resistant coating to protect against surface erosion
• have a minimum 20 year warranty protecting against surface deterioration and maintaining trafficability, and have a BRANZ Appraisal or CodeMark product certification.

If the sheets are non-trafficable, they must be laid over netting or mesh. The netting or mesh must be:

• strong enough to hold the weight of an adult if the sheeting gives way
• plastic coated where possible, especially in areas exposed to the elements
• fitted in the opposite direction to the run of purlins – these are the beams on the roof that the sheeting is fixed to – and the purlins must also be placed no more than 1200mm apart before horizontal timber spacers are required.

Plastic roof and wall cladding materials - Glass fibre reinforced polyester (GRP) – Standards New Zealandopen_in_new

Interior application

Translucent sheets used within buildings and directly exposed to interior spaces – including walkways or verandas with side-walls where smoke can accumulate – have the following requirements.

• Products with a Fire Group rating of 2 must be used.  
• Where the material is:
  • non-flammable or self-extinguishing, there's no restriction on continuous use of the material
  • flammable, each sheet shall be separated by a sheet of metal roofing.

Rules for walls

When installing translucent plastic sheeting to walls, position the sheets at least 2 metres above external ground level, or 2 metres above internal floor levels, whichever is higher.