When it comes to design and construction, there are factors that often impact the decisions faced when considering external sheathing. Generally, the construction industry has been able to select from:
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Cement sheathing board
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Calcium silicate sheathing board
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Magnesium oxide sheathing board
This decision-making process is driven by various factors and the different sheathing board types may perform well in numerous areas while lacking in others. Some of the main considerations revolve around cost-efficiency, passive fire protection, and ease of use. Choosing the wrong type of external sheathing board can have an impact on all of these areas.
In recent years, alternative sheathing board types have reached the market. One of these is the gypsum-based sheathing board. At Klasse, we believe that the qualities this sheathing board possesses make it the number one choice for the construction industry. If you read on, we’re going to show you why.
What is a gypsum-based sheathing board?
Before taking a look at how this option is preferable to cement, calcium silicate, and magnesium oxide board, it’s worth considering what a gypsum sheathing board is.
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate and is widely used to manufacture wallboards that are used to cover walls and ceilings. Gypsum boards often consist of a core of set gypsum surfaced with specifically manufactured paper firmly bonded to the core. Klasse gypsum-based boards are coated with fibre-glass paper, making them both moisture resistant and non-combustible.
In the UK, and the US, gypsum sheathing boards have historically been used in the construction of commercial buildings. As time has gone on, those in the industry have realised that this also performs exceptionally well when it comes to residential settings, even within a single-family home.
The key benefits of gypsum sheathing board
Waterproof exterior sheathing
When looking at any exterior wall sheathing, the weather protection that is offered needs to be one of the main considerations. The UK is somewhat unique in terms of the weather that is experienced, but there is no getting away from the fact that waterproof qualities are a must in construction here.
Gypsum sheathing board is made with water resistance at the forefront. It comes with a specially treated core and fibreglass facing that helps to provide a barrier to water and air infiltration. This means that, as well as protection from water, there is also a resistance to moisture.
Mould resistance
As you’d expect with waterproof exterior sheathing, there is also a level of mould resistance here too. Our exterior gypsum sheathing has glass mat facers which are naturally moisture and mould-resistant. Within its core, you’ll also find that it’s treated with additives that have water repellence and anti-microbial qualities.
While this protection is indeed important, it’s also worth noting that gypsum sheathing board also maintains permeability. This means that water vapour is still able to escape before it goes on to cause any other issues.
A1 fire-rated gypsum board
When it comes to any sheathing board types, fire protection is up there as the top priority. Experiences and incidents in the past, such as Grenfell tower have highlighted just how important passive fire protection is and how it can truly save lives.
A1-rated sheathing, such as that offered by Klasse, means that those working within the construction industry can have confidence that they’re complying with building regulations as well as providing the standards that ultimately save lives.
Gypsum sheathing board and the environment
With COP26 came a whole new focus on construction and manufacturing processes and how they have a negative impact on the environment. With governments across the world signing up and agreeing to change, there have been particular challenges faced in construction. The reality is that gypsum sheathing board manufacturing is undeniably an energy-intensive process. However, on the whole, this is a product that is known to be more environmentally friendly than its cement-based counterparts.
Gypsum has been highlighted as being an energy-saving material. That’s down to the fact that calcination processes take place at temperatures that are significantly lower than with concrete. We’re looking at temperatures as low as 135 centigrade being compared to those as high as 1,400. The result of this is that fuel consumption and C02 emissions are minimal.Another plus when looking at the environmental impact of gypsum sheathing board is the fact that it’s recyclable. Once the paper outer cover is removed, gypsum is fully and recyclable and, as a consequence, gypsum waste is one of the few construction materials for which closed loop recycling is possible. Unfortunately, there are a limited number of recycling plants that offer this service on a large scale in the UK at present, the key here is to only use the number of boards that are needed at the off, but there is reassurance in knowing that recycling is possible.
A final factor to consider is the weight aspect. When compared to other sheathing board types, gypsum is certainly lighter. When compared to those which are concrete-based, gypsum is around 30% lighter. This means that, when it comes to transportation, there is a reduced environmental impact.
What are the other benefits offered by gypsum sheathing board?
There are plenty of considerations when it comes to selecting a sheathing board, and amongst the top of these are the levels of robustness and durability.
The good news with gypsum sheathing board is that it is both robust and durable. In terms of this area, this is what you can expect:
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A high-density product that provides passive fire protection and mitigates wind and installation damage.
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A product that comes with high impact resistance and impressive pull-through strength.
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Exterior sheathing boards that have been rigorously tested and achieve BS EN 1354-1 (90-minute fire protection).
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A product that is A1 fire rated and non-combustible.
Beyond this, there is a need for those in construction to know that they have a product that’s easy to work with. The likes of cement sheathing boards and magnesium oxide sheathing boards are not highly regarded when it comes to this.
When you choose gypsum sheathing board instead, you can expect:
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A sheathing board that is extremely easy to work with. Given that it is 30% lighter than cement boards, you’ll find that this is so much easier to handle.
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Gypsum has no requirement for any power tools. In fact, it can be cut with just a knife, this also ensures that dust levels are kept to a minimum.
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The attraction of working with gypsum is that it’s so much easier to curve than the alternatives that exist.
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Project costs are lessened as there is often no need for an additional breather membrane.
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As far as waterproof sheathing is concerned, gypsum sheathing board is water resistant, the Klasse G-board carries a 12-month exposure guarantee.
What else is there to know about gypsum sheathing board?
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Buildings with a timber frame
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Light steel infill and oversell systems on concrete and steel frame buildings
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Light gauge steel frame buildings
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Modular buildings
This is yet another benefit of a gypsum sheathing board: it’s extremely versatile.
The big features that are worthy of further exploration all centre around the safety aspect here. A1 fire rate gypsum sheathing board has these additional benefits:
If additional insulation is installed there is no detrimental impact on the fire performance. When humidity increases, there is an extremely stable substrate which will only enlarge by fractions of a millimetre when facing increased humidity.
Gypsum locks moisture in its core, should there be a fire this would lead to a reduction in temperature and this would not act as fire fuel when it’s being used in a façade capacity. In fact, it actively reduces the transmission of fire.
Final thoughts
While the likes of cement, calcium silicate and magnesium oxide sheathing still have a place in the industry, the truth is that gypsum offers numerous benefits that make these the exterior sheathing boards of choice. The level of fire protection offered, as well as the ease with which this product can be worked, make it more than just a little appealing.
Beyond all of this, we also have the environmental impacts to consider. If construction is going to make the change, and prove itself sustainable, then a move over to gypsum sheathing board should be considered.
Our G-board, a gypsum-based external sheathing board is the first in a range of sheathing boards that we intend to bring to the market. We can also discuss C-board (cement-based external sheathing board), S-board (100% calcium silicate external sheathing board) and M-board (mixed calcium silicate external sheathing board).
