The main purpose of a typical cavity wall construction is to enhance insulation and safety.
A cavity wall also known as a hollow wall is a wall constructed with an air space or cavity between two separate walls called the outer wall and inner wall. The air space provides insulation against energy loss (thermal conductivity). Cavity walls are built for many reasons, but the chief advantages of cavity walls are that they provide protection from extremes of weather such as heat and moisture as the cavity insulation with the damp proof course makes a building warm in winter and cool in summer. They act as fire breaks to prevent the spread of fire across the building and they are relatively cheap to build. Cavity walls were developed in the early 20th century, and they became common in the UK from the 1920s. A cavity wall is made up of two leaves: an outer wall called outer leaf and an inner wall called inner leaf. The space between the internal leaf and external leaf is called a cavity. The brick thickness of the cavity can be any size, but it is usually around 50–75 mm (2-3 inches). Metal ties and concrete slabs are used to hold the inner and outer brick leaf together.
The main purpose of a typical cavity wall construction is to enhance insulation. Generally, exterior walls also known as the outer leaf of the wall provides all-around weather protection, you can expect your home to be warm in winter and cool in summer, no matter how severe or extreme the conditions are outside. And the vertical damp proof course within the cavity wall thickness protects the internal and external walls against moisture as well.
The inner wall surface also protects against fire, which means that you will gain peace of mind knowing your property will be safe if there were a house fire. You can often use dowel to extend the use of the cavity wall.The disadvantages of a cavity wall include the below.
Generally, there is more air leakage and heat loss in a cavity wall than in an equivalent solid wall.
Cavity insulation makes the outer brick leaf colder and damper which can lead to metal wall tie corrosion.
Without a proper damp proof course, cavity walls are more prone to moisture due to the cavity separating the two leaves of the wall.
Cavity walls are difficult to insulate, which means you may need professional help when applying cavity walls insulation.
Installation of fixtures such as electric sockets inside the cavity can be tricky.
Because of these factors, it’s important to understand exactly what's involved in building a cavity wall before you go ahead with your project. Unless you have plenty of time and patience and demand good insulation from your home, then we recommend that you consider other types of walls for your property.
Yes, electric sockets can be installed in cavity walls. However, it is important to note that the installation process can be tricky and it’s often best left to a professional electrician. Make sure you consult with an expert before attempting this type of installation.
In addition to enhanced insulation and protection advantages of cavity walls, cavity wall construction also provide a degree of acoustic and thermal insulation. This means that if you have a cavity wall, your home will be warmer, quieter and less prone to sound transmission from outside with an additional benefit of reduced cooling cost. A solid brick wall has the tendency to slowly draw rainwater into the wall. In a cavity wall, the cavity acts as a medium to drain out rainwater through weep holes. Weep holes are strategically placed holes at the bottom of the wall system that helps drain any water or humidity that can damage the wall. If you’re thinking of building or renovating your home, it’s important to understand the benefits and disadvantages of different types of walls.
The easiest way to find out if your home has a cavity wall is to look for the presence of an air gap between the interior walls and outer walls. This space is usually around 50–75 mm wide (2-3 inches) and the maximum vertical spacing is around 450mm. If you can’t see the air gap, it doesn’t mean that your home doesn’t have a cavity wall as it may just be hidden behind plasterboard or another type of finish. To find out for sure, you can use a metal detector to locate the presence of metal ties (the metal plates that hold the two masonry walls together).
Cavity wall construction is a job for a professional. Unless you have plenty of time, patience and experience, it’s best to leave this type of project to the experts. Cavity wall insulation can be expensive to build, so it’s important to make sure you get the job done properly the first time around.
Cavity wall construction details includes building two dry-stacked or masonry walls separated with an air space or cavity between the outer leaf (exterior wall facing the outside of the building structure) and the inner leaf (interior wall). Brick cavity wall consists of metal ties that are then inserted across the gap to hold the outer leaf and inner leaf together. A reinforced concrete foundation slab of structural steel is placed beneath the internal and external leaves before they are joined using various types of construction adhesive and plasterboard, fire breaker, insulation material. Finishing materials are applied to each side of the cavity wall. It's important to ensure that a flexible vertical damp proof course is provided at the doors and windows reveals to prevent moisture from entering.
Cavity walls are mostly installed in older homes, as modern construction methods tend to favour other types of wall assembly. Cavity wall insulation is typically found in brick veneer homes, non-loadbearing cavity brick homes, concrete slab on ground homes and timber frame homes that have been constructed with a cavity between the inner and outer leaves.
If you’re installing an insulation material to your cavity walls, it’s best to leave the air gap alone as a continuous cavity as this is actually what provides the insulation value for your home. If you really want to fill your cavity, use plasterboard or another type of fireproof finish material instead. Other materials such as mineral wool or cellulose can also be used to fill the cavity, but they’re not as effective at preventing a fire from spreading. It's also important to provide a damp proof environment within the cavity to protect the wall against moisture.
Yes, in addition to the many advantages of cavity walls, sound insulation can also be installed in them, generally to the external face of the internal wall. This type of insulation is usually made from mineral wool or cellulose and it helps to prevent sound transmission from one room to another.
If you’re thinking of installing acoustic insulation in your home, make sure you consult with an expert to find out which type of cavity wall insulation will work best for your needs. Sound insulation materials may use a mineral wool insulation made from natural rock.
Take a look at YourHome for more information on brickwork and cavity walls.