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We believe that a roof is the most integral part of a home. It’s what holds your walls together and keeps your house, your possessions, and your family safe and secure.
Roofing: A Guide to Lead Valley Installation
Wind pressure is a common cause of failure for tiled roofs. As the wind moves over the roof it produces upward forces causing the roofing tiles to rattle or be removed completely.
Contrary to common belief, roofing tiles are not "blown off" a roof. The wind creates an upward force as it travels over the roof, causing the tiles to be sucked upwards. It is important to understand this subtle distinction in order to build a more secure roofing system. Securing tiles against upward lift is the key to keeping the tiles on the roof.
As the wind travels over the roof area, it causes the air pressure on top of the roofing to decrease. At the same time the pressure underneath the roof increases. The increase in pressure inside the loft space results in a positive pressure on the roof tiles. The negative pressure above causes the tiles to be sucked upwards, lifting the tail of the tile. The lower the pitch of the roofing, the higher the forces will be.
If the tiles are being sucked upwards rather than blown, the old method of roof tile fixing may not be the best. Traditionally roof tiles are nailed or pegged at the head or top of the tile. This secures the tile against the force of gravity but has little effect on upward tile lift. In fact the only thing securing the bottom of the tile is the tiles own weight.
Tests in the United Kingdom have proved that a roofing tile clipped or secured at the bottom can withstand 5 times the force of a head nailed roof tile. Tiles can be clipped or wired to ensure the tail is secured against wind uplift. This also stops the annoying rattle or chatter sometimes associated with wind swept roofs. The chatter occurs as tiles are lifted and dropped by the wind vortex. I prefer to use a bead of silicone between the tile courses to act as a second line of defence against tile chatter.
It is important to note here that modern roofing tile clips must be installed correctly if they are to have any effect. Tile clips are usually nailed in close proximity to the interlocking channel. Because of the risk of damaging the tile, there is a tendency to move the nail too far away from the interlock. The clip must be positioned at right angles close to the tile. The roofing clip should be securely bedded to prevent the tile working loose. In my opinion, the old system of wiring the bottom of the tiles is superior to modern clipping. The wire fixes to an eyelet on the bottom of the tile and in between tile courses onto the supporting baton. This has the effect of clamping down the tile. I have re-roofed wired roofs that are over 50 years old and the wire is still clamped tight.
The most important roofing component when it comes to preventing wind damage is the roofing felt. Roofing felt or sarking is placed under the batons before the tiles are fixed. The primary function of all roofing felt is to prevent wind damage. The waterproofing of the paper is far less important than its ability as a wind barrier. The sarking prevents the increase in pressure inside the loft, thus preventing wind uplift. It must be fixed securely with 150mm overlaps. An extra baton should be placed at the point where the sheets overlap to prevent wind travelling between sheets. If the felt is not correctly secured the wind force will be focused on the weak spot causing more problems.
All ridge and hip tiles need to be mechanically fixed in areas prone to high winds. Roofing mortar alone should not be relied upon to hold these tiles secure. Once the bond between tile and mortar is broken the tile can work loose. They should be nailed, clipped or wired.
The areas most lightly to be submitted to wind uplift are the eaves, verges and ridges. In these areas it is prudent to take extra precautions with your tile fixing. Nail and clip all tiles around the periphery.
A little extra time taken at the installation stage will ensure the roofing tiles stay secure in heavy weather. The extra cost is outweighed by the savings in maintenance and piece of mind.
How To Stop Roof Tiles Being Blown Off
In Australia, roofing materials usually fall into one of two possibilities: concrete roof tiles; or corrugated metal roofing with a bonded paint finish (known in Australia as Colorbond, or CB). Which option is best for your situation? Both will keep the weather out, so weigh up the factors below before you decide.
A Bit of History: The concept of bonding paint to a galvanized base originated in Chicago, and was further developed in Australia into a product that has remarkable corrosion resistance and is aesthetically interesting: Colorbond©. It comes in many standard colours and is resistant to the elements. Whereas a galvanized corrugated roof might last 20 years, a Colorbond roof would have a 50 year life or longer.
Terra cotta tiles are also an option; they literally last forever. Think archaeological dig. There are examples of terracotta roofing that have been around for 1000s of years. However it is about double the price of a concrete tile roof.
For our purposes, we will compare concrete roof tiles and Colorbond roofing, and will focus on Melbourne conditions. Both products do an admirable job at what they're designed for (keeping the weather out). Concrete roof tiles have been used in Melbourne for at least 75 years and there are many houses in older suburbs such as Heidelberg and Camberwell that still have their original concrete tile roofs.
Why would you select one product over another? It comes down to personal taste, lifestyle, a few other factors... and COST.
Architectural Merit: This is a personal matter. Colorbond has a modern stylish look with clean lines. However, there are many concrete roof tile profiles that give a different architectural result than a standard half-pipe tile. For a small addition in price, you could (for instance) select a flat shingle style. There are also many colours in concrete roof tiles.
Noise: This is an important consideration. Insulation and ceiling notwithstanding, you will hear rain on a Colorbond roof. While we might think of raindrops falling on a metal roof as a pleasant sound, it can be disturbing to some people, especially in heavy downpours. Tile roofs are much quieter.
Water Collection: If you want to collect roof water in a tank for household use, Colorbond is the best option. You will harvest more water because concrete tiles have a level of absorbency. Also they tend to retain dirt, dust and so forth which washes into the water tank. During the recent 10 year drought in Melbourne, home owners were encouraged to collect rain water for household use. This influenced the demand for Colorbond roofing.
Weight: Colorbond is a fraction of the weight of a concrete tile roof (10% to be precise!) So your roof framing can be much lighter. Also, a Colorbond roof is no heavier wet than dry. A concrete tile roof will absorb water before it runs off, so a wet tile roof is heavier and engineering specifications need to allow for this.
Rodents: It is simpler to make a Colorbond roof pest-proof by nature of the way the product is installed.
Bushfire: Melbourne is a city adversely affected by summer bushfires. If you are building in the outlying fire-prone areas, BAL (Bushfire Attack Level) regulations will make it in your interest to choose a Colorbond roof, as they are easier to seal against external ember attack.
Resilience: If you need people to climb on your roof for maintenance reasons, Colorbond is more resilient. However, if you need to penetrate the roof (for instance for a vent or air conditioning) this will be more expensive with CB.
Eaves or Veranda. If you have extensive verandas or eaves, a Colorbond roof will be more desirable because of its lighter weight. With verandas you want a shallower roof pitch, and this can only be achieved by some form of sheet roofing. Typically roof tiles are not recommended on a roof pitch of less than 20 degrees. And because Colorbond is a descendant of old-fashioned corrugated steel, this delivers the traditional Australian veranda look.
Cost: Concrete tiles are over 20% cheaper than Colorbond, which is why more than 90% of homes built in Melbourne have a concrete tile roof. The advertising might have you think that CB is as cheap as tiles, but this is not the case. Designers sometimes prefer Colorbond. One client paid to have plans drawn up by a designer. When seeking quotes, they were horrified to see thousands of dollars extra for a Colorbond roof, when they actually preferred a traditional tile roof.
Which roof is best for you? Look at each factor as it relates to your situation. Weigh up its degree of importance, and then decide which roofing material best serves your particular needs, tastes, lifestyle, and budget.
Roofing is one of the most important investments you can make. Improper, aged or substandard roofing can lead to a host of other more expensive problems. If you are selling your property, a well-chosen roof can yield a solid return on your investment. Whatever your budget or design desires, whether you want architectural shingles, tile roof installation or something in between, a Roof Master consultant will work with you to make it a reality.
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