Cavity Walls: Cavity Wall is a type of wall structure, in which there is an open space or cavity that is left between two layers of brickwork. it is also known as an Hollow Wall. The gap that is left between the two brick layers is known as the leaf that is inside and the outer leaf. In modern buildings, the gap is closed with Cavity Wall Insulation (CWI) which is an insulative substance. This is carried out during construction, rather than injection like when it’s retrofitted. Buildings with cavity walls were first introduced sometime in the 19th Century and became widespread by the 1920s.
Initially they were built without insulation, and they were slightly smallerthan the typical their size is typically between 4 and 10 centimeters. However, there are many instances of home owners having CWI retrofitted. From the 1970s insulation in the cavity became standard and by the 1990s building regulations forced it to be installed in new construction.
When building Cavity Walls, or Cavity Wall, the two brick skins are joined with what is commonly referred to as Wall Tie. Wall Tie which are usually made of metal. The wall was constructed using tie made of iron, mild steel or copper, but these materials were prone to corrosion and wall tie corrosion was first discovered in the 1960s. After that, they began to use stainless steel as it is less susceptible to corrosion and that helps keep the structural integrity intact for longer. Do you need wall tie specialists? Get in touch with our team today.
The walls were first designed and constructed to stop problems caused by damp. The cavity is there to stop water from getting into the building’s interior and helps built up moisture and water escape from the wall by the use of weepholes. These are small gaps in the wall’s external pointing that allow the water to drain from that are generally placed every 1 meter on the exterior leaf.
Walls made of concrete differ greatly, as they handle water in a different way due to bricks being porous, it is quite simple for moisture to pass from the external to the interior wall, causing an impermeable damp issue, so to combat this walls must be much more robust, which means they cost more to build. They also are less efficient since they don’t offer much heat or sound insulation due to the existence of an air gap inside the cavity.
It is important to know that CWI can lead to damp problems, and can increase the severity of an existing damp issue, or increase the likelihood of wall tie failure. It is typically due to the wrong type of insulative material being employed in the cavity, as it isn’t letting the wall breathe and dry up excess moisture. It acts as a “bridge” to carry the moisture to the wall, creating an issue of damp, but more modern and natural materials can be utilized which allow the wall to breathe better.
Advantages
The walls could allow for some resistance to fire.
They reduce the chance of condensation, moisture build up, and penetrative damp issues.
The cavity wall is a great way to reduce the cost of heating an entire building. Since the air in the cavity works as an insulator.
They provide excellent sound insulation in comparison to houses that has a brick wall, reducing the effect of sound from outside.
The economics of Cavity Walls are cheaper to build than walls that are solid as they don’t require as thick.
It provides protection from efflorescence. They are white marks on the external brickwork which appear the wall when water has entered the wall, leaving crystal salt deposits.
The wall ties are all the thing that connect the two walls , and they are impervious to moisture. Because there is no direct contact between the two branches of the wall, there is hardly any possibility of water getting into the wall. The wall was designed to stop rain penetrating the wall and transferring towards the interior.
Avantages
Cavity Wall construction is more challenging than the construction of a solid wall. it requires plenty of supervision in its construction phase to ensure it is done properly.
The amount of expertise required is greater when building cavity walls. Therefore, expert architects Highly skilled masons, highly skilled laborers are required.
There is always the possibility that moisture could penetrate from the exterior leaf of the wall and reach the interior of the wall, as the cavities were not really designed for filling with materials.
If the material that is insulative gets damp, it could lead to cold bridging or thermal Bridging. It is the practice that involves heat passing through an object which can be more permeable than surrounding materials.
Retrofitting CWI to a wall cavity might result in air pockets not being filled, causing ‘cold spots’ in the interiors of the wall that could draw condensation.
As mentioned earlier wall tie corrosion is also an issue. When wall ties are fitted with CWI , the outside leaf becomes colder and gets wetter. It can also speed up the process of corrosion of wall tie, and there is no way to replace wall-ties sufficiently.
If you want to install CWI, the thickness of it will be limited by the size of the cavity. This will differ from building to.
Problems with CWI
For certain people Cavity Wall Insulation could be extremely beneficial. It can reduce energy bills and keeps your home warm for longer. The issue is that it can be caused by retrofitting cavity wall insulation or if you’ve had it installed previously, you might already be facing problems. In most properties the cavity is designed to be a cavity so filling that space with CWI material could contribute to the development of a penetrative damp issue.
If there is a reduction in airflow around the cavity , it is likely that water will be unable to evaporate. Also if the insulative material becomes saturated , it will trap moisture close to the inner leaf, and act as a bridge to allow moisture to pass through the cavity, again contributing to damp issues with penetrative penetration. It is not just this, but it could result in moisture being placed near the flooring joists, leading to flooring rot, and eventually flooring failure.
We have also seen a lot of cases of cowboy contractors who have failed to install CWI, which is why there’s a significant number of homeowners who found themselves with a home that is less efficient as the CWI was not installed properly and the gaps without insulation are left in the wall, creating cold spots which later cause condensation spots in the interior wall.
This can cause issues in the event that the building is made of timber or steel, since the cavity is utilized to prevent moisture from the structure’s frame. If the cavity is lined using CWI then moisture will be permitted to remain close to the frame which can lead to rot and corrosion of the frame which can lead to structural problems.
