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A Quick Guide To Structural Reinforcement With Cast Stone
Cast stone’s strength, durability and its ability to withstand compression makes it an an ideal material for producing a vast range of commercial and residential architectural solutions. Suitable for newbuild projects, retrofit and restoration commissions, cast stone provides our clients with so much versatility.
Our in-house manufacturing team frequently produces the steel cages and bars required to provide additional structural reinforcement to many of our clients’ weight-bearing components. Working with a structural engineer, our highly experienced team are able to precisely produce the bespoke cast stone components our clients require.
In this week’s blog, we provide a quick guide to structural reinforcement with cast stone.
Why is cast stone so suitable for these particular situations? It’s all due to its different properties:
- Strength
- Ability to handle compression
- Suitability for period and contemporary buildings
- Suitability for property refurbishment
However, in order to provide the most suitable material possible for its various uses, it’s important that cast stone undergoes reinforcement by adding concrete around a cage or bars made of steel. This gives the best of both worlds: a composite material with the ability to withstand compression while having the tensile strength of steel.
Here, we’ll discuss the causes of structural damage, the reasons why structures need structural reinforcement, and the benefits of such reinforcement.
What causes structural damage?
Ultimately, it’s a failure of the material to do its job. That is, to support itself and whatever is above it. So damage occurs when the weight of the loadings – including the weight of the piece of cast stone itself – exceeds what the materials can take.
For example, if a window head is supporting 16 stories of brickwork, it will get damaged if it isn’t reinforced – and reinforced correctly.
It’s therefore essential that any structural reinforcement is assessed by a structural engineer to determine the requirements, and that this is carried out effectively and precisely by an experienced team.
Why does a building or portico need structural reinforcement?
Structural reinforcement is a key component of stone used for building, including for porticos. Typically, a portico is made up of two columns at the front with a porch back to the building, and a beam spanning the two columns. The beam therefore needs to be supported on the wall and columns. Because of this, it needs a tolerance to bend, so that it doesn’t crack.
How does this happen? Through the use of structural reinforcement. There are a number of uses for structurally reinforced cast stone, including:
● Window dressings
● Balustrading and parapet screening
● Façade stonework
● Porticos
● Wall dressings
● Columns and pilasters
More contemporary properties – such as those with large structural openings or large glass windows – typically need structural reinforcement. That’s because there’s a need for longer beams to support the glass, and these beams need to be reinforced to make sure they don’t fail.
But it isn’t just large pieces of stonework that need structural reinforcement. Even when working with smaller pieces, it’s important to take the forces around the structural member into consideration. So while the process of reinforcement is key, it’s also essential that a structural engineer is involved throughout the process in order to make sure the stone is up to the job and can cope with the forces exerted on it.
And engineers aren’t just critical for the production of the cast stone; they’re also important for installation too.
Ultimately, if there’s a need for structural reinforcement and it’s not provided – either at all or correctly – the material will fail, leading to cracking, snapping and general damage.
The benefits of structurally reinforced cast stone:
Structurally reinforced cast stone can be used as a material in its own right or as a base for a natural stone cladding. That’s because cast stone has a number of benefits, including:
● It can be reinforced relatively easily
● It’s strong and durable
● It eliminates the need for joints
● It can save time
It also has an attractive aesthetic, which is often used for many modern buildings. Aside from its strength and durability, its time-saving benefits are probably one of its greatest advantages.
Where once sections of cast stone were made then assembled around the job (where a builder installs shuttering and wet pours concrete on site), we can supply cast stone that’s already cured, meaning it can be used straight away.
This saves time as there’s no need to cure onsite over three or four days, meaning there’s no need to wait before continuing a project; a beam can be hung in the morning and the build can continue at pace without the need to delay while the concrete takes time to cure.
This makes it a perfect choice for a variety of building projects.
How is cast stone structurally reinforced?
While it’s clear how beneficial structurally reinforced cast stone is as a building material, it’s important to understand why – and this comes down to how it’s manufactured.
There are a number of well-established steps we take when it comes to producing structurally reinforced cast stone:
1. Firstly, it’s important to identify the requirement for structural reinforcement. This involves an engineer looking at the stone and working out whether reinforcement is necessary. They’ll then supply the calculations and the details of what’s required.
2. These details are sent to our team at Haddonstone, and we’ll get to work on making the cage or bars that reinforce the stone, as well as the moulds for the cast stone. When producing beams and other structural stonework, we manufacture them from wet cast and reinforce them. That means we use a steel cage or bars that go across the length of the beam, and it’s this that stops the structural failure.
3. Moulds that contain structural reinforcement are marked up, and they’re checked to make sure they have the necessary amount of steel inside. These moulds can come in various sizes, depending on the project, so it’s important that they’re checked thoroughly.
4. Once the mould is made, it goes to the onsite engineer. They make sure it’s all correct, and the mould goes off for casting.
We use a wet cast, and this combines with the steel reinforcement to form a composite material. This combines the benefits of both materials into one – the strength of the cast stone and the relative flexibility of the steel.
5. When the stone has been cast and the pieces have achieved the requisite strength, they’re demoulded and placed outside to cool off. The site manager will use a lifting socket to move it around site.
Following this process, each piece has a 99 year life expectancy – a time period that’s dictated by the design criteria. It will need maintenance during this time, but this is worth investing time and attention into as it can help extend the life of the stone.
This process is the same whether the stone is needed for public or residential purposes. The real difference comes with logistics.
For instance, if the stone is needed in a residential area – or if there are large pieces that need to be delivered for a public project – it can be difficult to manoeuvre cranes into position. There are also often more onerous site restrictions to contend with in public spaces.
So it’s important that these are considered when working on any kind of project.
Is structurally reinforced cast stone bespoke?
Most structurally reinforced cast stone is bespoke made – especially if there’s a requirement for a single piece (perhaps for aesthetic reasons), rather than multiple pieces. It’s therefore vital not only that a structural engineer is part of the process, but that it’s manufactured by a team with skill and experience.
That’s where Haddonstone comes in. Our team understands the importance of structural reinforcement for cast stone, and knows that it’s a suitable material for a range of different uses.
We use our extensive knowledge to make sure that the reinforcement is applied correctly, reducing the impact of moisture ingression and preventing the steel reinforcement from popping through the stone – which can cause damage and lead to structural problems.
As well as this, we work with structural engineers to make sure the cast stone we produce reaches a certain strength of Newtons before it gets demoulded, so that it can withstand any necessary stresses without damage.
Whatever your project, you can rely on Haddonstone to provide structurally reinforced cast stone that’s been developed using years of expertise.
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Our experienced and friendly team has been helping clients complete their projects, with and without structural reinforcement, for the past 50 years.
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