Damp on Internal Walls

Damp on internal walls

Damp on Internal Walls

Can cavity wall insulation cause damp?

Of the 27 million homes in the UK, there are an estimated 20 million that are “cavity” or “hollow” wall construction, with more being built daily.

It has been the predominant form of construction from the 1920s to the present day. However, they were built as early as the 1890s. They were even referred to in Roman times by Vitruvius, who wrote a book, “The ten books on architecture”, where he identified that building a wall with two leaves was beneficial. He was well ahead of his time!

Why Cavity Wall Construction

Cavity walls have an outer leaf and an inner leaf. The outer leaf gets all the rain and wind and has a void of air; therefore, the inner wall leaf always remains dry, which means it is warmer than the cold/wet outer leaf.

Additional benefits are the air cushion between the leaves, forming some insulation and thermal properties. It was also considered cheaper to build as fewer bricks were used. It is a great concept and has been a fantastic way to keep homes warmer and dry for many years.

A cavity wall property is robust and, in many cases, keeps poorly maintained buildings dry as the outer leaf takes all the strain for dampness and upkeep issues, leaving the internal leaf dry and well-maintained.

It is not always easy to determine if a property has a cavity wall as the outer leaf can be one brick width with just a 2-inch cavity with a half-inch inner leaf, so it can sometimes be tricky to detect unless you measure. There is usually a pattern of brickwork with cavity constructs that a surveyor will be able to identify in a survey.

Defects in Cavity Walls

Defects can include when wall ties have been installed incorrectly, not at all or unevenly spaced. When loading to the wall, an aerial is put on an outer leaf; for instance, it can pull the outer leaf away from the building as, without the cavity ties, there is no strength.

There have been cases, even in the last five years, where due to poor workmanship (not enough wall ties installed) on a modern building has led to its collapse.

BRE 401 contains much information regarding cavity walls and wall tie replacement

Thermally Efficient Walls

Cavity walls are thermally efficient if left to be a true cavity.

Unfortunately, in more recent times, the idea of “cavity wall insulation” has, in many cases, caused issues.

Placing a material/foam substance within this air void, it “bridges” the two walls. If the outer leaf allows moisture to pass through, this gap joins the two walls, and moisture and dampness will migrate from the outside to the inside wall, often leading to damp on internal walls.

Damp on internal walls

Sometimes even a gutter leak can introduce moisture into the cavity, and if insulation is present, it will get wet and cause damp on internal walls. In many cases, we have had to open the walls and remove the insulation and check for electrical faults; wall ties corrosion and timber moisture levels to ensure the building structure is robust.

Diagnosing The Problem

The first sign is often damp on internal walls. However, the best way to diagnose the problem is to remove bricks in the external wall and use a camera “endoscope” to find out what is occurring.

We want to find out what materials are in their mineral wall or expanded polystyrene balls.

Once the wool is wet, it gets heavy and drops to the bottom of the wall causing cold bridges. The use of thermal imaging camera equipment is also useful in these surveys.

Urea Formaldehyde – expanding foam – is less common. It naturally breaks down and eventually loses its insulation benefits. It is also exceedingly difficult to remove once in place.

In short, a cavity wall is a great benefit in a home. However, if insulation is put into the cavity and it gets wet, it can cause multiple damp issues and additional costs to remove the damp materials.

South East Timber and Damp Limited are a leading specialist company in mid-Kent, serving all of Kent, including Tunbridge Wells, Sevenoaks, Tenterden, Maidstone, South East London and surrounding areas.

Meet Dean & Annabelle Webster, Owners of South East Timber & Damp Limited.

If you wish to find out more about our services, please drop us an email: [email protected]

Want to chat in person? Call us: Sevenoaks 01732 884535. We are based in Woodchurch TN26

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