FAQs & Myths

Frequently Asked Questions & Common Roofing Myths

Frequently asked questions
What is re-roofing?

Re-roofing is the industry term for replacing a roof.

Why do I need a new roof?

You might need a new roof because your roof has lost its colour, or there are signs of corrosion, rust, mould or even leaks. Once your roof has stopped protecting your house from the elements then it needs to be replaced. It might not be obvious, as your roof can be leaking into the roof cavity without you knowing it. The reason could be old age, wrong fit for its purpose (wrong material for the environment), poor maintenance or structural reasons (poor design/installation).


For a list of signs that you may need a new roof see our re-roofing guide.

How much does it cost?

There are many variables that go into the cost of a re-roof, so it is impossible to give an estimate without sighting and measuring your roof.


For some key consideration when getting estimates check out the estimate section in our re-roofing guide.

Is corrugate made from iron?

No - corrugate is no longer made from iron. Instead, corrugate (longrun) is now made from either sheets of pre-painted steel or aluminium strengthened for use in construction.


The corrugate that Dimond Roofing sells today is made of steel, produced by New Zealand Steel at their Glenbrook steel mill and delivered to Pacific Coil Coaters, (also known as ColorCote) for painting, before being roll-formed at Dimond Roofing branches nationwide.

Should I replace the insulation in the ceiling space?

It’s a lot easier and quicker to install insulation when the roof is off. Insulation in the ceiling is where you can make the biggest difference in keeping your home warm. Replacing your insulation when your roof is off is easier and often cheaper than replacing it through the ceiling. Your insulation may need replacing if it is under 12cm thick, has holes or pieces missing, or has gotten wet and damaged.


Find out more about insulating your roof.

What materials are roofs made of?

Roofs can be made from many different materials including iron, steel, shingle, asphalt, concrete, membrane, bitumen and clay. It all depends on the look and style of your home, as well as the environmental factors. In New Zealand most residential homes have either longrun steel, pressed steel tile or concrete roofs.


To see a list of pros and cons for different roof materials see the choose section in our re-roofing guide.

What about my gutters, downpipes and other rainwater systems?

Your gutters, downpipes and rainwater system are an important part of your roof. Make sure these are maintained and clear of debris, holes, and are securely attached to your roof. Blocked gutters or gutters installed at the wrong angle can cause water to overflow which can get behind your fascia, leading to leaks into your home. Also check your gutters for ponding, as this can lead to corrosion and water overflow.

How many estimates should I get before selecting a roof installer?

Most people like to get two or three, but keep in mind that a low price can signal a lot of discrepancies and shortcomings in the reliability of the installer. If you’ve gotten estimates, make sure you’re comparing apples with apples e.g. edge protection, removal of the old roof, product e.g. Kiwisteel (imported product) vs. NZ made (ColorCote or Colorsteel), Gerard Roofs tiles vs FeRoof (Imported tiles).


For some key consideration when getting estimates check out the estimate section in our re-roofing guide.

How long is reasonable to expect to wait after I select an installer for work to begin?

Four to six weeks, weather permitting. This can vary depending on the time of year and the installer’s workload, however the installer has a responsibility to be straightforward about his availability right from the start.


For more information on the installation process see the install section in our re-roofing guide.

What is the typical duration of a re-roofing job?

This depends on the size and/or complexity of the roof: a small, uncomplicated roof job can be finished in two days; whereas a large, complex project can take around a week. Once started, a job should not be interrupted for any reason other than weather. However, if a problem arises in the process, it might be necessary to halt the work to negotiate any changes to your agreement.


For more information on the installation process see the install section in our re-roofing guide.

How does extreme weather affect re-roofing projects?

Bad weather (rain, snow or high winds) can interrupt or postpone roofing projects. The safety of the workers is the first consideration; the second is keeping the house dry.


For more information on the installation process see the install section in our re-roofing guide.

Should I expect to pay a deposit when I sign an agreement?

Yes, to secure the materials but we don’t recommend you pay for the total job up front.


For some key consideration when getting estimates check out the estimate section in our re-roofing guide.

What is a flashing?

A metal covering or channel used to stop water penetrating the junction of a roof with another surface. Most often used at seams or joints and in valleys where runoff is concentrated.

What is a purlin?

A support board for a roof. An example is a horizontal wooden board between the rafters of a roof, that supports roof cladding.

What is a batten?

A narrow timber, steel or polystyrene member attached to a roof or wall structure, used to attach metal cladding, metal tiles, shakes, or shingles to the structure. Also known as counter-batten.

What is longrun steel?

Longrun is typically known as corrugated iron – however it is no longer made from iron. Instead, longrun is the generic term for sheets of pre-painted steel strengthened for use in construction by having a series of alternating grooves and ridges roll formed into it. Improvements in paint technology mean products such as ColorCote® and Colorsteel® provide robust substrates for roofing and cladding that will cope with the harshest environments. Longrun comes in many different profile shapes now – not just the tried and true Kiwi classic corrugate.


Find out more about longrun steel

What is a dissimilar metal?

A dissimilar metal refers to when two different metals are subject to corrosion when they come in contact with each other or from water run-off. Also known as Galvanic corrosion, it occurs when two different metals are in contact in a corrosive environment, and one of the metals experience an accelerated corrosion rate.

What is edge protection?

A guardrail or restraint designed to prevent a person from reaching over a roof edge or falling from a height.

What is chalking paint?

The formation of white chalky powder on the surface of the paint, this often occurs as paint weathers and sunshine and moisture degrades the paint surface.

What is horizontal overlapping?

Where short sheets of longrun are joined together and end lapped to form the overall roof run from ridge to gutter.

What is ponding or pooling water?

Any free un-drained water retained after it has stopped raining on roof cladding, Flashings or a gutter due to insufficient fall, or to permanent deflection or deformation of a roof.

What are fixings?

The method of attaching cladding to the frame achieved by the use of fasteners.

What are fasteners?

Nails, screws, clips, and bolts, which are used to fix components of a roof assembly together. Also known as Fixings.

What is my roof pitch?

A roof is described by its pitch: (a) Less than 5 degrees is Flat, (b) 5 to 15 degrees is Low-pitched, (c) 15 to 30 degrees is Pitched, (d) 30 to 60 degrees is Steep-pitched, (e) Over 45 degrees is known as Cathedral (f) Over 60 degrees is defined as a Wall.

What is underlay?

An absorbent permeable membrane that absorbs or collects condensation or water, that may penetrate the roof or wall cladding. Also known as Building Paper.

What does ridge, valley & profile mean?

Ridge: The top of a ridging or profile or roof, where it’s reached its highest point.
Valley: A gutter at the internal intersection of two sloping planes of roof cladding where the roof pitch is 12 degrees or greater.
Profile: The cross-section of metal cladding, generically known as corrugated (sinusoidal), ribbed (trapezoidal), troughed, boxed or tray.

What does a 'run' mean in tiled roofs?

The run is the horizontal row of tiles across the roof.

What is fascia, eaves & downpipes?

Fascia: It’s the long, straight board that runs along the lower edge of the roof. The fascia is fixed directly to the roof trusses and usually does the work of supporting and carrying all the guttering.
Eaves: The protruding edge of a roof slope. When enclosed, it is known as a soffit.
Downpipes: A pipe used to carry roof water from gutters and roof catchments to drains or storage tanks

What is roofing substrate?

The metal surface to which a painted finish is applied, that is then formed into your roofing profile (such as corrugate) and cut to size.

What are snow straps?

A metal support strap that goes across from the roof to the gutter, to secure the front edge of the gutter on the bracket, this limits the gutter disengaging from the bracket after a heavy snowfall.

What do roof hips and raking cuts mean on my roof?

Hip: The external angle formed on a roof where two inclined faces meet.
Raking Cut: When you cut across the sheet at a non-right angle.

What are drip edges & sealants?

Drip Edge: An outward projecting edge formed on a metal flashing, to direct water away from the building or to avoid capillary action. Also known as Birds beak, Tip, Kick, or Break.
Sealant: A single or multi-component polymeric material used to waterproof metal joints, in conjunction with mechanical fasteners.

Roofing Myths
It takes a long time to get a re-roof done

It doesn’t take long to get your roof replaced. Generally speaking, a job can be completed in under a week depending on the size and complexity of the roof (and any adverse weather conditions). You might need to wait for the project to start depending on your roofers’ workload, but they’ll communicate with you around their availability prior to starting a job.

I have to move out of home whilst my roof is replaced

No, you don’t need to move out. Your roofers will work to remove and replace your roof, ensuring your home stays dry during the process. They might ask you to move some things to clear access to your property, but it is perfectly liveable whilst the roof is replaced. Note: It is worth letting your insurance company know you’re having your roof replaced to ensure your house insurance covers you whilst the process is happening.

Corrugate is made from iron

No – corrugate is no longer made from iron. Instead corrugate (longrun) is now made from sheets of pre-painted steel strengthened for use in construction.

A roof lasts forever

No – a roof is not designed to last forever. With maintenance a roof will last a long time, but it does have a lifecycle. Under the Building Code in New Zealand roofs need to last a minimum of 15 years, however most roofs will last a lot longer when maintained properly.

You can just paint over the rusty bits

Painting over the rusty bits doesn’t address the issues of weather tightness or stop the corrosion from continuing to occur. All it does is hide the problem, meaning you can’t see it get worse, or any potential ingress of water.

All roofers are cowboys

Unfortunately there are cowboys in the roofing industry, however most are not. A good qualified roofer is an expert tradesman, there is a lot of skill in putting a roof on properly. Check your roofer is an LBP (Licensed Building Practitioner) and a member of RANZ (Roofing Association of New Zealand), this way you know they’re governed by a code of practice and have a high standard of workmanship.

You can just do it yourself

We don’t recommend re-roofing yourself, purely because it is a specialised trade. Ensuring your roof is weathertight takes an expert who knows about flashings, and correct installation. We’d hate to see you have problems down the road with leaks, by not using a properly trained and qualified roofer.

If it's not leaking, surely it's okay

Just because you can’t see leaks, doesn’t mean there are no hidden problems with your roof. And just like your car, it is better to maintain your roof and fix problems early than to let it degrade completely past the point of no return.