A roof is a vital part of any building and it has multi-functions.
Not only does it need to be weather resistant, keeping out rain, sleet and snow but also strong enough to resist storms and high winds and protect the interior of the building from any damage.
It also has to help prevent infestation by insects or other pests, be able to retain heat in the cooler months, yet provide shade and ventilation for the property when it’s hot.
The roof structure itself has to be strong enough to support the tiles or coverings and able to transfer such load down the walls to the foundations of the building.
Over the years concrete and steel have been the primary choice of material for commercial buildings, with wood mainly used for roof structures in residential properties. However, there are a variety of other materials that are used to build roofs, and these include wood, stone, clay, glass, metal and polycarbonate roofing sheets.
Yet, it’s only been over the last 20-30 years or so as concerns about global warming and CO2 emissions have come to the fore that major concerns about the contribution of the construction industry to such issues have surfaced. As a result, greater efforts are being made to find building materials which have a less negative impact on the environment yet still meet the primary functions and designated minimum statutory requirements.
Herein we’ll take a look at some of the issues with roofing materials.
Some characteristics to look for when choosing roofing materials
Several key considerations come into play when roofing materials are being considered :
- expected life of material, ie can it resist or is it particularly susceptible to the elements of weather; does the material have a long life-span, or does it corrode or rot or lose its strength when wet; accordingly, will frequent repairs be required?
- can it withstand lengthy wet or dry periods and/or withstand wind or storm forces and the forces of the building itself as it expands and contracts with changes in temperature; .
- is the material easy to use and work into different shapes; what about its weight or thickness?
- importantly, is the source of the material renewable, is it eco-friendly, and can it be recycled or not?
- does the material comply with building regulations as they relate to fire, loading etc?
- cost can also be a major factor.
What are the most popular materials for roof construction and why?
The two most popular materials for constructing a roof are steel and concrete. There are a variety of other materials used as coverings for the main roof structure and these include clay tiles, concrete tiles and slates:Steel
Steel
is uniformly strong, flexible, and workable. Its high resistance to stresses can be calculated in detail and steel structural members can be made in a variety of shapes. These members can be joined by steel bolts and welded to produce fused joints which are firm and help distribute stresses between beams and columns.
Steel is usually protected against corrosion by coatings on its surface, although alloys such as stainless steel have been developed for exposed surfaces.
Concrete
Concrete is a mixture of cement and water, with added aggregates of sand and stones. It has low tensile but high compressive strength and hardens rapidly by chemical combination to a stone like solid.
The addition of steel mesh makes the concrete much more versatile than either individual products of steel or non-reinforced concrete. Such concrete is ideal not only for constructing roofs but also for foundations, columns, walls, floors, and a wide variety of coverings.
Roof coverings, some popular ones
Interlocking concrete tiles or clay/pantiles
One of the most common types of roofing around the UK is interlocking tiles of different materials. Concrete ones are a cost-effective option often seen on both residential or commercial properties. They can easily and quickly cover a large area and offer cost effective weatherproofing for the building, at a relatively reasonable cost.
Clay or pantiles are used for both traditional and modern designs as well as in a wide range of styles and colours.
Slate
Slate has been a roofing material for many centuries and became particularly popular in Victorian times. It has a long lifespan and is a mid-range priced roofing material. Slates, however, are heavier than some other materials so strengthening of the roof structure may be needed.
What’s the estimated CO2 contribution of roofing materials?
Generally, the construction industry has been found to be a major contributor to global warming. Concrete currently accounts for about 8% percent of the CO2 being emitted into the atmosphere and is comparable to that of the entire agriculture industry, which stands at 9%.
For every ton of steel produced in 2018 emitting on average 1.85 tons of CO2, or about 8% of global CO2 emissions.
These are major numbers and, so, if the industry is serious about helping to tackle global warming, more effort needs to be put into developing and using more eco-friendly materials.
What other materials can be used in roof construction to improve sustainability?
There are numerous other more eco-friendly materials which can be used in roofing materials and these include bamboo, recycled plastic, straw, rammed earth, hempcrete and timbercrete.
But the main ones are:
Reclaimed or recycled wood or metal
Recycled or reclaimed wood or metal is a long-lasting material that does not need frequent replacement. As well as being water and pest resistant, it tends not to burn or warp, making it a viable option for roofing, structural supports and building façades.
Many building materials have highly embodied energy levels within due to the energy required to produce them. However, each time a material is properly and efficiently reused or recycled, its embodied energy level is lowered, and the material becomes sustainable because the whole raw extraction and processing steps are eliminated.
Pre-cast concrete slabs
The sustainability factor of pre-cast concrete slabs is higher than most traditional poured concrete options. This is mainly because the slabs take much less energy to produce and assemble. Furthermore, pre-cast concrete can be properly cured in a controlled environment, instead of potentially exposing it to a variety of unfavourable conditions on a construction site.
Ferrock
Ferrock can withstand more compression than concrete before breaking and is far more flexible, being up to five times stronger than concrete. Ferrock actually absorbs and traps carbon dioxide as part of its drying and hardening process which makes it not only less CO2 intensive than traditional concrete, but actually carbon neutral.
Final thoughts
Now that more and more developers and builders are re-thinking construction techniques and their choice of roofing materials, spending some time looking at roofs is an important part of the exercise. This is especially so given the high CO2 emissions of two of the more favoured roofing materials, namely steel and concrete.
Selection of roofing materials can be made on the basis of embodied energy, pollution levels caused and length of life. Consideration can also be given to recyclability, and or the greater use of second hand slates, concrete and clay tiles.
It’s inevitable that alternative, more sustainable materials will continue to come into greater use. Bi-products from existing materials such as Ferrock which originates partly from steel dust.
If you want to find out more about sustainable roofing materials keep researching new products as they begin to appear on the market. After all, the primary objective is to help the construction industry do more to combat global warming and better protect the environment.
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