External Wall Insulation in South Wales

If you live in South Wales, external wall insulation could be a great option for you.

Most properties in the UK are of masonry construction – so your ‘bricks and mortar’, but the process of how we go about insulating their external walls varies quite a bit. If a property in South Wales was constructed before the Second World War, it is very likely to be of solid construction (so a single skin of brick, 220mm to 250mm thick) with plastering internally, then actual brick or some render on the outside (the render came much later). Usually properties from the 1950s were built from cavity walls (270mm to 310mm thick), with an air gap in the middle of two layers of brick or thermal block with brick on the outside.

If you have ever driven through The Valleys, you will have noticed the miles and miles of terraced properties that are part of the view. Those properties were built in the late 1800s and early 1900s following the mining boom and other associated industries taking off. These properties were mostly built with solid construction. Terraced solid construction is also common in metropolitan areas such as Cardiff, Swansea and Newport, and semi-detached properties built in the 1930s are also common in some of the older sub-urban areas of those towns and cities.

Previous government funding schemes that were very generous (and probably never coming back in their old forms), allowed for a large volume of retrofit insulation projects in South Wales. These took place across Newport, Cardiff and right down past Bridgend, mainly targeting cavity wall properties, since the cost of the measure was much cheaper than retrofitting solid walls.

Typical property construction in South Wales


However due to the nature of cavity wall insulation there were problems, either because properties were either not suitable for retrofit insulation (structural reasons), but also due to the high exposure areas in the south-west of the country (higher winds and more damp weather). In addition, an independent body carried out a survey of 250,000 CIGA-guaranteed cavity wall properties in Wales, of which half had cavity wall insulation failure. A large proportion of these were in the South Wales Valleys.

Why does cavity wall insulation fail in Wales?

As mentioned briefly above, South Wales is particularly susceptible to cavity wall insulation failure because of its characteristically wet weather!

Unfortunately, although cavity wall insulation can be effective, it can also be a nightmare if installed incorrectly. The material can form a bridge from the exterior wall to the interior wall, which rainwater travels across and causes damp indoors. It can also slip over time, meaning it is unevenly dispersed in the cavity, and therefore ineffective.

Some opportunistic tradesmen over the years have installed cavity wall insulation in properties where it is just not suitable – for instance those which are privy to driving or consistent rainfall. The insulation material is never going to be able to withstand these conditions for long. Also many properties are rendered and some of this render, due to the nature of it has failed, but not picked up on the surveys – with the properties then being pumped with cavity wall insulation, it has made the damp problems worse!

This is why we suggest external solid wall insulation in these cases. In fact, even properties with functioning cavity wall insulation can benefit from the measure.

Why get solid wall insulation in South Wales?

There are several reasons why solid wall insulation is a great alternative. Firstly, there is no limit to the thickness of insulation you can install on external walls, unlike in the cavity, which can only be so wide. This means bigger energy savings and higher levels of thermal comfort. Walls store warmth and slowly release it back into the home. For example, 90mm of EPS attached to a traditional 9-inch solid brick, will reduce the U-value (which is a measure of how much energy is lost) from 2.2 down to just 0.3 per m2K, bringing it very close to the standards of a newly constructed wall. As a result, you can expect energy savings of up to 40%.

Another advantage of solid wall insulation is that it gives the exterior walls a waterproof covering. It also stops penetrating damp. Because it raises the temperature of external walls, the reduced temperature of walls indoors and outdoors is reduced, thus lowering the risk of condensation and damp in your home.

Here are some typical properties we have picked in South Wales with solid brick construction, and as you can see pretty old render as well. Therefore much of these properties are in desperate need of an upgrade, both in terms of the thermal properties and external appearance.


Typical semi property with old render in Bridgend



Typical solid wall property in Cardiff, South Wales

What properties can look like when upgraded with external wall insulation in South Wales?

Having interviewed a number of contractors that carry out some fantastic retrofit projects in the area, you will see a selection of some of their work below and transformations that have transpired on the properties in question.


Terrace property retrofitted with external wall insulation in Newport, Wales. Contractor: Be Constructive, Wales


Ex-clothing manufacturing plant outside Cardiff converted into 2 domestic units and retrofitted with EWI. Contractor: Proewis Ltd


Aside from protecting your walls, you can choose from a huge range of colours and textures of render – or even replicate a brick look using the brick slips. The work normally takes about 2-3weeks to complete (weather permitting), but the contractors may take longer if the external weather conditions are not great.

Choosing the right contractor may be tricky and sometimes it is a minefield to know where to start. If you have any questions or you need a recommended company in your local area (Newport, Cardiff or Bristol), then let us know and we should be able to help.

If you live in South Wales, the Bristol Channel or the surrounding areas and are interested in solid wall insulation then fill out the form below for a free, no-obligation quote from one of our partners.

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