The Most Common Building Materials
This post is going to cover the most common building materials. It is intended to be an overview of the materials used in structural design and it will be condense. As an engineer, architect or as someone just doing general construction you will encounter hundreds of different types. I could write a list but it would be quite dry to read. Therefore a summary of the different materials you would find yourself using on a daily basis is covered here and it is certainly not an exhausted list.
I must give a warning, I am biased towards steel. Its my favorite!
Are Some Materials Better Than Others?
As an engineer, and not only a structural engineer, but also mechanical, civil, aerospace and stretching as far as anyone involved in construction, the choice of materials in the design stage is one of the most critical factors.
Coming from a structural engineers point of view, we need to satisfy the clients brief (the requirements) by providing a safe, durable and cost effective solution. If for example, my client wants a long span bridge, designing a bridge out of glass is going to be extremely expensive. Ergo, not the correct material for the brief.
We are now going to look at the three major materials commonly used in construction. Steel, concrete and timber. We will evaluate the pros and cons and I’ll attempt to explain why in some counties steel is used and others concrete is used for very similar designs.
Posts in this site will be very much related to steel, concrete and timber but we will also look at other building materials such as masonry, glass and special plastics entering the construction industry thanks to new research.
Do Countries Have a Preference?
This may sound a bit strange, but depending on the country will also depend heavily on the types of building materials you will most commonly see. Why? Well it is one heavily dependent upon what is available locally, as this reduces transport costs but it is also a lot to do with the labour costs.
Lets look at Norway for example, a quick google of houses there and you will see a lot of timber construction. Wonder why? Well its landscape and environment has plenty of forests and therefore timber. On top of this, the labour is also expensive in Norway for economic reasons.
Timber House - Norway
However, if we look at Hong Kong, we will see a lot of concrete structures. This is due to the fact that labour is cheaper, therefore having more people on site during the construction phase is not as harmful for the overall construction cost. On top of that, concrete is used a lot more for high rise buildings.
Steel As a Building Material
Steel is one of the most popular building materials in the world and the preferred choice by a lot of designers for not only commercial buildings but it is also in growing demand for residential buildings. Their are significant advantages to using steel over other materials, we will look into all of these but first lets explore the properties.
Properties of Steel
Steel can be made in many different forms, such as universal columns (UC) and universal beams (UB), hollow sections such as circular (CHS), square (SHS) and rectangular (RHS) and many others. This creates a lot of variety for engineers to work with and utilise and take advantage of the geometric properties. This means that steel can have exceptional strength both tension and compression.
Advantages of Steel
Sustainability. We need to look after our planet! Using steel reduces the carbon footprint of a building, this is predominately from being able to recycle steel. We can also fabricate the steel in factories prior to taking it to the construction site, thus reducing congestion and pollution as well as waste.
Efficiency and speed. One of the most important aspects of a development project, can we keep the costs down? Increased build time typically increases the overall cost. Speed and efficiency are not only found on site whilst getting build, it begins in the design office. Steel design has a good selective of commercial software, for both the structural analysis of the members and connections and also detailing which is then relayed for the fabricator. It can also be estimated for preliminary design with a good degree of accuracy, useful for estimation purposes! Once on site, steel erection gangs work quickly with minimal downtime.
Steel Erection, taken from www.geograph.org.uk
Safety. As already mentioned, steel is fabricated off-site, this makes the site a lot safer for the construction workers. Quality control is also a major plus with steel, grades of steel, the type of steel, information about the process is all tracked. This means we know exactly where the steel came in a steel frame.
Disadvantages of Steel
Machinery. One of the major flaws with steel is the actual fabrication process. Did you know for example that the connections for a steel frame can typically cost upwards of 20% of the steel price. Fabrication requires skilled welders, platers, heavy machinery and CNC machines, all of these come at a cost.
Erection. So, it may be safer and faster to erect the steel but weather conditions can be a nightmare for the site manager. Cranes don’t fare too well in windy conditions halting work all to often!
Corrosion. Although this is easy to deal with, if ignored it can cause a lot of problems, especially with insurance. This can be remedied by regular maintenance checks, although this is a cost that needs to be factored in.
Concrete As a Building Material
Concrete is one of the oldest building materials, used as far back as Ancient Greece. It is a material that has dominated high rinse buildings in the past century due to its sheer strength and versatility.
Its an exciting time for concrete currently with a lot of research going into fibre-reinforcement headed by research worldwide, most notably EMPA in Switzerland.
Properties of Concrete
Concrete is simply amazing in compression. However, it does not fare to well in tension. Therefore to counter this, we include reinforcement to provide tensile resistance. The norm at present is using steel reinforcement, varying in diameters to suit the area required to resist the tension forces.
Advantages of Concrete
Strength and Versatility. The main reason to use concrete as a building material. It can be made into any shape with the use of creative form work to suit complex geometries normally suggested by the architect. Concrete also gets stronger over its life span.
% of Compressive Strength vs Time
Maintenance. The less we have to worry about the state or condition of the structure in the future, the better it is commercially. Concrete requires next to no maintenance at all. It bodes well in many temperatures and can be designed with environmental factors in mind.
Sustainability. Concrete to an extent can be recycled and used again and again for one of the main ingredients, the aggregate. So its therefore good for the environment. On top of this, concrete can be made of site and then delivered, providing the same benefits as steel.
Disadvantages of Concrete
Site Work. The biggest flaw, in my opinion with concrete is the time it takes to build with it. Now in planned correctly and manged with this in mind, the delays will be minimal. Concrete takes time to strengthen. Form work is also required and in complex projects will require skilled work, therefore needing a joiner.
Mesh Reinforcement & Other types used in Concrete
Material Properties. Concrete is not good in tension as discussed and therefore reinforcement is required. Not a major issue now as knowledge of composite action and information in codes of practise to aid the structural engineer is excellent.
Remedial Works. Retrospectively altering a building can be troublesome and costly if concrete is involved. Unless the exact position of the reinforcement is used in the reinforcement clashes can occur and it can be hard to prove the structural capacity is adequate.
Timber As A Building Material
The ideal of materials for residential properties, especially in the United Kingdom as well as many other countries. A lightweight building material, easy to both fabricate and take to site allowing for quick erection.
These can be found in traditional pitched roofs, typically made out of trusses. Support the floor systems with joists and be used as lintels in short spans.
Recently their is a lot of interest into the use of structural timber for use in high rise buildings. Canada at the time of writing (2018) has at least three in the pipeline.
Properties of Timber
Timber has a higher structural capacity per unit weight than steel or concrete. Even I was shocked when I found that out!
There is no reason why timber cannot be used for any brief. Going forward, the use of timber in construction is trending.
Advantages of Timber
Weight. As already mentioned, time has a higher structural capacity per unit weight than steel and concrete. This provides massive benefits during the erection stage as less machinery/lighter weight machinery will be required.
Build Time. Very similar to steel, it is fast to build. No waiting around for the strength to increase as with concrete.
Work-ability. Possibility the great advantage of timber over steel is work-ability. If an error occurs on site, and yes they certainly do a lot, it is possible to fix with the aid of a good joiner.
Disadvantages of Timber
Environmental Factors. Timber is arguably the least environmentally friendly material to use for construction. Problems lie with sourcing the material as it can hard to find it locally and the cost. Although this is very opinion based, as other professionals argue that timber is grown faster than it is being used. Personally, I would imagine this rises and falls within the supply and demand of timber.
Aesthetics. If done correctly timber can look beautiful. If the timber is not treated properly and maintained, it can start to get discoloured. This will naturally occur over time (also being a disadvantage of other materials too).
So, this sums it up for the three major building materials. Steel, concrete and timber. Each one has their use, using each material to their advantages can make a project a lot cheaper and environmentally friendly. If possible before starting any project, a look into whats available locally should be considered.