Looking at roofing repair secrets

After spending over 20 years investigating the cause of leaking roofs in Sydney…

There has been so much learning about roof leaks and how to repair those leaks.

After a while, all the information that I uploaded and lumped into categories, became a mess and hard to find.

So, the Roof repair Table of Contents  below makes it simple for you to scroll down, find what you are interested in and then dive into the ‘Rabbit Hole’.

Hope you find what you are looking for…

Table of Contents for This Website



What is the difference between Zincalume and colorbond?

Both ‘Zincalume’ and ‘Colorbond’ is uniquely Australian because it is made only by Bluescope.

The original corrugated roof sheets were imports from England. They used a zinc coating to protect the base steel (iron) from rust. These were the original ‘Corrugated Galvanised Iron’ roofing material and can still be seen on old buildings throughout Australia.

Bluescope developed a more durable coating made of zinc and aluminium – to replace the galvanised coating. They called it ‘Zincalume’.

Then in 2013, they made ‘Zincalume’ even better. And it is now called ZINCALUME® steel AM125

Colorbond is simply ‘Zincalume’ steel that Bluescope puts through their special paint coatings factory.

What colours do colorbond come in?

Bluescope keep coming up with new COLORBOND colours and finishes.

New colours were introduced and unpopular colours were discontinued. It got so confusing that Bluescope had to finally break their colours down to 5 different ranges.

There are currently 14 ‘pale’ colours they have put in the ‘Contemporary’ range.

There are only 8 surviving traditional colours – and these live in the ‘Classic’ range.

Recently, they released 5 colours in a matt finish. These matt colours are more suitable for walls than roofs.

Fences have their own colour range, and there are only 14 colours.

Then finally the ‘Ultra’ range (suitable for severe environments) contain only 6 colours. It seems like people who live by the seaside deserve only a few colours.

Go here for more on colorbond colours

How do I know that you have genuine colorbond?

Bluescope is not the only company who manufacture painted roofing material in Australia.

ACE gutters have traditionally manufactured their own roofing and guttering material. It is of a similar product to the Bluescope products and ACE call their painted steel ‘Duracote’.

There is an easy way to find out if your roofing and guttering is made from genuine Colorbond.

What is Colorbond Ultra?

Sea water is very corrosive. Steel and salt water do not mix well. Steel loses the fight in the early rounds. So Bluescope came up with a roofing material that can withstand salt spray for decades. They call it Colorbond Ultra.

From my research, it is not a secret type of steel that is used. It is the same steel – but the zincalume coating is a bit thicker. The paint system appears to be the same.

The official Bluescope information is :

The distances are less (you can use 'ordinary' colorbond within 100m) if the marine environment is like the Sydney harbour or Parramatta River...

Colorbond "STAINLESS" is just stainless steel with a colorbond finish - so the corrosion resistance is provided by the stainless steel. It is the most expensive of the colorbond steels.

Colorbond "ULTRA" has the same steel base as standard colorbond. The main difference is the grade of the zincalume coating used. "ULTRA" uses the higher grade (thicker) AZ200 zincalume - and this gives it the higher corrosion resistance, and a premium price (but still cheaper than "STAINLESS").

Is Colorbond better than Zincalume?

The emperor with no clothes is just like Zincalume. Dress him up and he becomes Colorbond. So, who do you think is better?

They are basically the same thing. And both perform the same duties and last about the same time. But, I would rather have the emperor with clothes than without.

What thickness Colorbond roofing to use?

The majority of colorbond roofing materials comes in 3 thicknesses.

Roof sheeting is either 0.42mm thick or 0.48mm thick. Roof flashings are usually 0.55mm thick.

The choice between the two roof sheeting thicknesses is not a function of how long they last. It is based on their strength to span between the support purlins.

But there is a reason I prefer to use the thicker 0.48BMT version


What is the minimum pitch for corrugated iron roofing?

5 degrees.

Traditional corrugated iron roofs are quite steep. Then most people thought they could use a corrugated roof sheet on flat roofs. This does not work.

Find out more about why roof pitch is important when choosing the correct metal roof profile to use.

Why are the ends of roof sheeting important?

A sheet of roofing material is watertight. When a series of roof sheets are locked together by a side lap, an area of roof is created to be waterproof. Besides any faulty side laps, the only way water can enter the roof is at the perimeters.

The two most important edges of the metal roof are the upstream end and the downstream end.

The upstream ends of the roof sheets must be able to stop water from climbing over the end (due to heavy rain and wind). And the downstream end must be able to stop water dribbling under the sheet and climbing up the roof sheet.

If you doubt that water can climb against gravity, find out about capillary action.

There are special tools made by the roofing manufacturers to help roofers turn the upstream ends UP and also turn the downstream ends DOWN.

This is not ‘rocket science’ – but we often see new roofs that look like the ends have been mistreated by a hammer to distort the ends. And that is apart from those roofs that have NOT had the blessing of any tool at all.

What is the correct way to lay a roof with end laps?

In the old days, all corrugated roofing iron came in ‘8 foot’ lengths. End laps were very common to get the length of roof sheeting needed for most roofs.

Then, we had long trucks. With them came long sheets. And the end of end lapping. It was a huge blessing.

But every now and then we are forced to end lap two sheets to get the length that we need.

So, what is the correct way to do this?

Why the side laps on roof sheets are critical to the function of a roof?

Engineers try to make their products as fool proof as possible.

Every style of roof sheet has some engineering detail on the side edge to stop the enemy of capillary action. Unfortunately, most roofers do not appreciate this engineering effort – and they try to install roof sheets that would have the roof engineer turn in his grave.

MORE coming soon.



What is the difference between terracotta and concrete roof tiles?

Terracotta roof tiles are baked from clay. The colour is either baked on or blended into the clay and baked.

Concrete roof tiles are manufactured from sand and cement and the colour is painted on.

Because of the manufacturing process and the raw material characteristics, terracotta roof tiles come in in more intricate designs and shapes - whilst concrete roof tiles are of simpler shapes.

The paint on concrete roof tiles will fade and weather away over time - whilst terracotta roof tiles will keep their colour. Both concrete and terracotta roof tiles have limitations on how flat they can be laid. These limitations are more on the tile design rather than the tile material.

Concrete roof tiles tend to be more resistant to breakage than terracotta roof tiles - although concrete roof tiles will generally chip more easily. Terracotta roof tiles generally have a more intricate interlocking lap and will not slide off even if they move off the roof batten. Concrete roof tiles can and slide off the roof if the holding hook moves off the roof batten.

Salt water can cause terracotta roof tiles to 'turn into powder' (fret) whilst concrete roof tiles are generally immune. So water front homes fair better with concrete roof tiles.

For those into roof repainting... concrete roof tiles can be repainted quite successfully to produce that new look - whilst terracotta roof tiles will resist the paint and cause paint peeling.

For those into costs... concrete roof tiles are slightly cheaper to manufacture and to lay. So a concrete tiled roof will be found on most budget homes.

How long does a tile roof last?

Terracotta roofs have been around longer than concrete tiled roofs - so there are more terracotta roofs that are too old to repair than concrete tiled roofs. Generally, concrete gets stronger with age and even though the tile manufacturers give a 50 year warranty, you should expect a lot more.

The older terracotta roof tiles tend to get brittle with age and these will break readily. The newer terracotta roof tiles do not have this tendency. Fretting (exact reasons not very clear) will shorten the life of terracotta roof tiles.

As a general rule, you can safely say that a tile roof will last a life time....

What are fretting roof tiles?

In the roofing game, "Fretting" is a term describing a roof tile (mainly terracotta) decaying into powder.

It is a problem that seems confined to terracotta roof tiles. I have not seen a fretting concrete roof tile yet...

For some reason, the terracotta does not like salt (and some other corrosive chemicals) - and the tiles turn into powder. So, terracotta roofs near the sea coast tend to have more fretting problems - although I have seen fretting terracotta roofs in the western suburbs of Sydney.

This means that there are other factors besides just salt that causes fretting.

Besides salt spray near the coast, swimming pool heating elements on roofs can produce a salty environment that promotes fretting. Home owners with pool heating on their roofs (especially salt water pools) should check for leaks on a regular basis. I have seen very bad fretting under leaking pool heating.

...Also, for more information and a video on fretting, go to my blog article about Fretting terracotta roof tiles in Sydney.

What is bedding and pointing on a tile roof?

The bedding is the mortar bed that is used to hold up the ridge capping and provide support to maintain the ridge capping in a straight line. Once the bedding hardens and the ridging is held firmly in place, a flexible pointing compound is applied over the bedding to provide a binding layer.

The pointing provides the waterproofing element and also binds the ridge to the tiles - providing security against dislodgement by winds and other forces...

There is a specific page on this website that goes to more detail about bedding and pointing. Take a look at this if you want more information.

...Also, for a video on why leaks happen at the bedding, go to my "roofing repair western suburbs sydney - how to repair a leak at the ridge capping" blog.

What is roof sarking?

Sarking is generally used under roof tiles. It is a reflective and water resistant membrane that is installed under the timber tile battens.

Sarking has reflective properties and this provides some insulation to the roof cavity.

The other reason sarking is used is because tiled roofs let in some water during heavy rain. During these occasions, moisture is then caught on top of the sarking and it dribbles down and finds its way into the gutter.

Sarking gets more important as the tile roof gets flatter 0r if there is a downpipe discharge on the roof. Tile manufacturers mandate the use of sarking on lower pitched roofs.

Where do I get a replacement roof tile in Sydney?

Roof tiles get upgraded quite often and also manufacturers come and go.

In Sydney, CSR Monier is the major tile manufacturer, followed by Boral tiles. So if you have a new roof and the roof tiler has not left you some spare roof tiles for your roof - then you should grab a tile off your roof one sunny day and head off to these companies to get some. Before they phase them out.

If you have an old roof, then the above companies will not have your tiles in stock. The handiest place in Sydney to get some replacement roof tiles is in Smithfield. See Shane and his team at Roof tile recyclers... Best place in Sydney for that hard to get spare roof tile.

For emergencies or if you can't find a spare roof tile to fit, most roof tiles with simple cracks can be repaired using roofing silicone quite successfully.

You just need to know how. See my "how to repair a roof tile = when you don't have a spare" post

What are roof valleys?

As soon as the shape of a roof gets more complicated than a rectangle, the roof has a change in angle. And the only practical way to build a roof with change in angles is to install valleys. Most people don't know that they have roof valleys - until a leak starts happening and a roofer tells them that the valley has a hole in it or it is blocked up with debris - or it has overflowed.

Roof valleys are one of the simplest flashings on a roof - but they can cause all sorts of problems. Go to this page to learn all about roof valleys and their problems.

Do I need weep holes under my ridge capping?

In a lot of situations, the pointing and the bedding will crack under the ridge capping and this allows water to seep through the cracks and pond on the top edge of the roof tile that is upstream of the bedding.

If this pool of water is not allowed to escape (via weep holes), it slowly builds up and will eventually overflow the top edge of the roof tile. This is usually why a tile roof will develop a leak only after prolonged rain.

There are numerous ways to fix this roof leakage problem caused by the lack of weep holes.

Also, the need for weep holes is not universal under every ridge cap. We have a lot more information about needing weep holes for roofs on this website.

More to come


Is a colorbond metal roof better than a tile roof?

It depends. Tile roofs are more common - so people must like them. There are differences. Just like some people love Holdens and others love Fords, It can be a personal thing...

But there are times when a colorbond metal roof is the only viable option. See my blog post on problems with flat tile roofs to see why this is so.

Generally, the differences are:

• Weight: A colorbond roof is much lighter that a tiled roof. This will mean less weight stress on the roof structure and the walls - leading to less movement induced cracking.

• Insulation: A higher rated insulation can be laid under a colorbond roof to enhance the insulation rating of the roof cavity. Tiled roofs only get a layer of aluminium sarking.

• Noise: The sound of raindrops is more pronounced on a colorbond roof. Tiled roofs are relatively quieter.

• Cosmetic appearance: Colorbond roofs can provide a more 'modern' look whilst tiled roofs give that 'traditional' look. This is very much a personal choice.

• Life of roof: Roof tiles have a longer warranty (50 years) because they do not rust. They generally do not get any weaker as they age - although terracotta roof tiles can 'fret' over time or if they are close to a marine environment. So, roof tiles will generally outlast a colorbond roof which generally lasts about 40 to 60 years...

• Maintenance requirements: The ridge capping on tiled roofs require repair/maintenance every 15 to 20 years. This is because the bedding and pointing will crack over time due to roof movements. This cracking can lead to water leaks. Roof tiles at the valleys do not get very firm anchoring and these can slip over time and leave a hole in the roof - causing a leak. Leaves gathering on a tiled roof will choke the drainage laps on the tiles and cause water leakage - so a tiled roof is better off without overhanging branches (dropping branches will also usually crack roof tiles). Colorbond roofs in comparison do not need the same maintenance as tiled roofs - they are virtually 'maintenance free'.

• Design and construction versatility: Designers can bend and curve colorbond roofs as well as making them steep or flat. Tiled roofs are limited to certain slopes to work. It is also very difficult to curve or bend a tiled roof. You can do more with a colorbond roof.

• Hail protection: I have seen huge hailstones put holes in colorbond metal roofs - although this is very rare. Hailstones usually just leave dents and the roof stays water tight during hailstorms. Dents on colorbond roofs do not usually affect the life or performance of the roof. Large denting on flat roofs may cause a problem with ponding - and in this case, local replacement od roof sheets are recommended by Bluescope. Roof tiles simply crack when there is a decent hailstorm - causing large amounts of water damage to the house. Tiles offer little protection against large hail stones.

• Spare parts: There are numerous shapes and sizes of roof tiles and as manufacturers go out of business or decide on a new marketing campaign, tiles are phased out. So, over time, some types of roof tiles will only be available if it is taken off an existing roof. Replacing a few roof tiles can sometimes prove very difficult. Corrugated metal roofing have stayed the same since inception - so you can find a piece of corrugated roofing quite easily.

The debate on Why replace a tile roof with a colorbond roof? continues...

Is a roof restoration worth it ?

Especially out in western Sydney, there are numerous street pole and fence mounted advertisements for Roof Restoration Services. Some starting from as low as $1400 for a full 3 coat system.

There is no national standard for a roof restoration. A restoration can mean many things and a $1400 roof restoration will not get you much. It often means a quick high pressure water wash followed by a certain number of quick, thinly applied coats of paint.

A roof restoration is usually sold as a necessity to maintain the roof properly. The only thing it does is to make the roof look new from a distance.

If I wanted to make my roof look good from a distance for a short period, then a $1400 roof restoration is a good deal. I usually tell clients that the only time I would consider a cheap roof restoration is just before I sell my house. Even then, I have no guarantee that I would add $1400 to the final sale value of my house.

If you intend to live in your home for a long time, then $1400 spent on a bathroom or kitchen will add more usable value to your home. Don't throw money at restoring a roof.

If you have a roof leak or want your roof maintained properly, then you want a decent roof repair and NOT a problematic ROOF RESTORATION.

More to come


How effective is a whirlybird at cooling my roof?

For some apparent reason, if you had Googled "How effective is a whirlybird", this website ranks number 1 or 2. And we do not want to install whirlybirds - because I think that they are rather ineffective (especially how they are generally installed - without eaves vents)

A whirly bird (if installed correctly) can be used to ventilate a roof attic - but NEVER think that a whirlybird can cool a roof!

Check out our webpage For more on the effectiveness of whirlybirds and user's comments

My ceiling is mouldy, Is my roof leaking?

If there is no water dripping through the ceiling (or a light fitting), and/or there is no brown staining, then there is a good chance that your roof is not leaking.

My website has been targeted by Google for mouldy ceilings! If you had searched for "why is my ceiling mouldy" - you will find me on the first listing. I don't fix mouldy ceilings!

So unfortunately, we are only of any good to you if your roof is leaking...

But I have the best information about mouldy ceilings on this webpage

Why is it important to stop condensation under your roof?

Most bathroom exhaust fans pump damp moist air into the ceiling cavity. If the the underside of the roof is cold, condensation occurs and water start dripping back onto the ceilings. This is not good.

All roofs should have sarking or anti-condensation blankets installed under the main roof element to stop internal condensation. Even patio ceilings should have anti-condensation. We will have a lot more information on the importance of the anti-condensation layer coming soon...

More to come


What is a box gutter ?

Wiki has excellent pictures and details about box gutters. In Sydney, most box gutters are constructed from sheet metal. And the main problem with metal is rust.

Box gutters made have to survive the most severe corrosive environment on any roof - so they should be made of colorbond metal as a minimum. Unfortunately, the cheaper Zincalume finish is often used instead because of perceived cost savings.

There are numerous problems associated with box gutters. For more information about how we deal with box gutter problems - go to our page "What is a box gutter".

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