This is a complete guide to steel-framed buildings. In this article you will learn about:
- the concept of a steel-frame house
- answers to common queries
- the pros and cons of steel framed buildings
To learn why building with steel is the most efficient way to construct a home, while understanding the drawbacks, read on!
What is a steel-frame house?
A steel framework is classified as being of non-standard construction as opposed to traditional house construction using wood frames. The steel frame is often not obvious, being hidden behind cladding, external brickwork or render.
Increasingly, more factories are making steel frames for the house-building industry using the `light gauge steel construction’ technique: light gauge steel is made from thin sheets of steel measuring between 1-3mm, which are cut and constructed using welding, bolting or riveting techniques, into the required shape at the factory.
On-site, they are fitted to concrete foundations before other materials are used to fill the structure of the house, such as brick or render.
Improvements to steel manufacture
Historically, steel has been regarded as a cheap construction method, used for instance, to build agricultural sheds, however, steel manufacture has undergone vast improvements and it is now considered a high-quality construction material with key attributes for modern building and could become more widely used.
The choice of any building material involves huge trade-offs, and it is difficult to optimise the design for any given situation because objectives such as cost, quality and aesthetics differ, points out Alan Muse, Head of Construction Standards at the Royal Institution of Chartered Surveyors. He said:
“Constructing houses from steel is not a new concept: it was commonly used to build houses after World War II. For residential construction, steel offers longevity; if it is fire-protected it will last longer than wood frames, and it is watertight. A disadvantage is that it is not so good at stopping noise, for example between apartments in a building.
However, steel is strong, therefore resistant to wind and earthquakes, it is adaptable and steel components can be made to any shape. It is particularly suited to the current trend for large spans in houses, as steel can span more quickly than cellular construction. It also encourages off-site fabrication which helps maintain high standards of construction.”
Mr. Muse added that while years ago steel corroded as it was not well protected, making it more difficult to obtain a mortgage for a steel built house, modern steel is of very good quality. Most steel production has a high embodied carbon content, which is a problem given the current focus on sustainability, but innovations are taking place to make low-carbon steel components and improve product quality.
These include the use of hot zinc coating, extra powder treatments and improved joining methods while low weight steel and mild steel are also being increasingly used.
While timber-frame construction is more sustainable than steel, it is more susceptible to fire damage; this is one example of the trade-off decisions which must be taken according to the location of a building, and different solutions may need to be implemented to achieve all the aims of a scheme.
However, if steel is well-designed and well-built, in many cases it can satisfy most scheme’s requirements.
Can I get a mortgage on a steel-framed home?
Problems with resale and insurance mean that lenders view steel framed homes with caution due to their record of variable build quality. Steel-framed homes are often bought by cash buyerd but it is possible to get a mortgage. However, the range of lenders is limited due to a history of defective steel based houses. Lenders are restrictive over the specific type of steel property they will grant mortgages on.
A mortgage broker may be able to help with a search for the right lender. Mortgage lenders define steel-frame houses as category A, B or C.
Category A means that a house is mortgageable in its original condition. The B category means that a property is mortgageable following approved repairs and the C grading rules out a house for being defective and it is therefore not mortgageable.
How easy is it to insure a house with a steel framework?
It is important to be aware that uncertainty surrounding the reliability of steel-frames creates difficulties in obtaining insurance, leading to the potential for higher premiums.
How can I identify steel in a property?
While steel framed buildings can be difficult to spot for a lay person, steel may be evident in the loft space and roof structure. It is also possible to see parts of a frame at meter entry points into a property, at the back of cupboards, or at areas of corrosion. Other tell-tale signs include patterned cracking on the skin of external brickwork and crooked internal door and window openings.
At auction, a buyer should be sure of whether or not the house they are bidding on has been built using steel, especially if an agreed mortgage depends on it.
Advantages of steel framing:
- They are cheaper than their wood frame counterparts.
- The vast majority of steel is recyclable.
- Modern steel-framed buildings have great structural integrity, being strong and durable and ideal for high rise building construction.
- Steel is fire resistant and does not warp or expand.
- It is faster to assemble a steel-frame on a construction site than a timber-frame.
- Steel offers customisable options; it can be used with brick, cement, wood and can also be painted.
- Steel is weather resistant; it deals with water damage better than wood and it does not rot.
- It is highly resistant to fungus.
- As steel-framed panels are grounded to earth, they work well as lightning rods for dissipating lightning bolts into the ground.
- Steel building parts can be ready-made off-site quickly.
- Great design flexibility which may be attractive to self-builders.
- In recent years the steel industry has developed its offer due to the benefits of off-site residential construction, which can include window and door frames.
Disadvantages of steel framed buildings:
- Difficulties in obtaining a mortgage and building insurance.
- A building survey is recommended before purchase rather than a HomeBuyers Report; this costs more but steel-framed houses are classed as being of non-standard construction. A building survey is a non-intrusive inspection and might not reveal structural problems if they are hidden behind the construction. A steel framework is difficult to identify without opening up the property walls and a surveyor may recommend that a further intrusive survey is carried out.
- Steel elements can corrode badly and develop structural issues, especially at the base of stanchions, galvanised steel windows and joining points, however, modern steel has enhanced rust resistance.
- Poor insulating properties and energy efficiency; steel is a conductive material, conducting heat 300-400 times more quickly than wood, reducing the insulation properties of wall insulation by 60%. This is due to thermal bridging: heat takes the most conductive path to dissipate. Thermal bridging can also cause black stains on cold areas of walls.
- Higher heating bills to counter the poor insulation.
- A steel framed construction makes it difficult to spot problems like subsidence and rising damp.
- On purchase, a larger deposit may be required and potentially a higher interest rate will be charged on a mortgage.
- Large amounts of energy are needed to manufacture steel, involving the burning of fossil fuels.
Do you have a view about steel built houses?
Let us know what you think. If you have experience of either buying or living in a property with a steel construction, we would be interested to hear your comments.