Does Your Decramastic Roof Contain Asbestos? What Homeowners Need to Know Before Re-roofing

What is a decramastic roof?

Decramastic roofing is made from lightweight pressed-metal tiles coated with a bitumen-based layer and decorative stone chips. It was widely used on New Zealand homes, particularly from the 1960s through the 1980s, and similar-looking metal tiles have continued to be manufactured without asbestos.

The word “decramastic” describes a style of roofing, not a laboratory result. Some older tiles may contain asbestos in the bitumen or mastic layer; newer tiles may not. Appearance and age can raise suspicion, but they do not prove whether asbestos is present.

How can I tell whether the roof contains asbestos?

You generally cannot tell by looking from the ground, checking the stone-chip colour or comparing your roof with an online photograph. Even an experienced roofer should not treat appearance alone as confirmation.

The reliable answer comes from representative sampling and laboratory analysis. The sample must include the relevant coating, not merely a loose stone chip. Because roof access and sampling can involve both asbestos and fall risks, homeowners should use a competent asbestos professional rather than trying to prise off a piece themselves.

• Check any original building, roofing or renovation records
• Ask whether a previous asbestos survey or laboratory report exists
• Give the sampler access to representative tiles or offcuts where this can be done safely
• Make sure the laboratory result clearly identifies the material and sample location
• Do not assume that one result covers a separate garage, extension or later roof addition

Why testing should happen before you accept a re-roofing date

If asbestos is discovered after the roofer has started lifting tiles, the site may have to stop while the material, debris and work area are assessed. That can affect scaffolding bookings, temporary weather protection, the roofing programme and cost.

An early result lets the homeowner, asbestos removalist and roofer agree on the sequence before work begins. It also allows the quotation to state who is responsible for access, isolation, removal, disposal, clearance, temporary waterproofing and handover to the roofing crew.

Do not water-blast, sand or grind an older decramastic roof

High-pressure water blasting can disturb an asbestos-containing coating and spread fibres and contaminated debris into gutters, downpipes, gardens and neighbouring property. Sanding, grinding, drilling and aggressive wire brushing can also damage the bitumen layer and release dust.

Do not sweep roof debris into a pile, use a leaf blower or put suspect tiles into general household rubbish. WorkSafe specifically includes decramastic tile roofs in its guidance for asbestos-containing roofing and gutter debris.

What about old debris in the gutters or roof space?

Weathering, foot traffic and previous roof work can leave chips, coating fragments and dust in gutters or around the roof space. If the tiles contain asbestos, that debris may also be contaminated.

Tell the asbestos contractor about visible debris, broken tiles, previous water blasting and any material that may have fallen into the ceiling space. The removal scope should cover the actual contamination found, not just the intact tiles visible from outside.

Is decramastic roof removal Class A or Class B work?

Decramastic tiles are metal, but the asbestos can be in the bonded bitumen coating. Intact asbestos-containing tiles may be suitable for licensed Class B removal when the material remains non-friable and the method avoids damaging the coating.

The condition and proposed method matter. Heavily weathered tiles, loose coating, contaminated dust or a process that makes the asbestos friable may require different controls or Class A capability. PropertyHelp reviews the survey result, condition and removal method before confirming whether the job fits its Class B licence.

How a planned removal and re-roof should work

The asbestos removalist and roofer should agree on the handover point before the job begins. Tiles need to be removed using controlled methods that minimise damage, then securely packaged, labelled, transported and disposed of as asbestos waste at an authorised facility.

The work plan must also deal with working at height, weather, residents, neighbours, power lines, solar equipment and protection of the exposed building. Any required independent inspection or clearance should be arranged before the roofing team takes over.

• Confirm the laboratory result and exact roof areas covered
• Agree who provides scaffolding and edge protection
• Identify soffits, fascia, gutters or other asbestos materials near the roof
• Plan controlled removal without unnecessary cutting or breakage
• Confirm asbestos-waste transport and disposal
• Agree temporary weather protection and roofer handover
• Keep residents and other contractors outside the controlled work area

Questions to ask before choosing a contractor

A useful quotation should say what material is being removed, what evidence supports the asbestos classification, whether access and scaffolding are included, how waste will be handled and what happens before the new roofer starts.

• Does the contractor hold the licence appropriate for this work?
• Is the asbestos survey or laboratory testing included?
• Who supplies scaffolding or edge protection?
• Does the price include waste disposal and any required clearance?
• Who coordinates the handover to the replacement roofer?
• What happens if damaged coating or contaminated debris is discovered?

How PropertyHelp can help

PropertyHelp Ltd is a licensed Class B asbestos removal company servicing Auckland and Waikato. We can coordinate testing, assess whether an asbestos-containing decramastic roof is suitable for Class B removal, prepare the site-specific removal plan, remove and dispose of suitable non-friable material, and coordinate any required independent clearance.

We also work directly with roofers and builders so the asbestos stage and new-roof installation can be programmed together. If the material or condition falls outside Class B scope, we will explain that clearly and recommend the appropriate next step.

Planning to replace an older stone-chip roof?

Do not wait until the roof is half-lifted to ask whether it contains asbestos. Send PropertyHelp the address, photographs of every side of the roof, the approximate area, any roofing records or laboratory report, and your preferred re-roofing date.

A small amount of planning at the start can protect the household and contractors—and prevent an avoidable delay once scaffolding and roofing crews are already booked.