How much does external wall insulation cost?

We have discussed external wall insulation a few times on this site, but we often get callers interested in EWI who then baulk when they hear the cost of the work. We want to make sure you are fully aware of what sort of costs are associated so I have come up with some guidelines and rules of thumb you can use to get an idea.

Size of your home

The simplest way to get an idea of cost is to look at the type of house you have. A detached house will typically cost £15-20,000 to completely insulate, a semi detached house £8-10,000, whilst a mid terrace is probably £6-8,000. The final figure will vary depending on just how much wall you have.

Type of Property Estimated Cost of External Wall Insulation
Detached £15 to £20,000
Semi-detached £8 to 10,000
Terraced £6 to £8,000

Wall area

A slightly more accurate way to work out the cost of the works is to add up the wall area that is going to need insulating. One of the London based installers we interviewed, Be Constructive, tell us that the average cost of one of their jobs is about £100/square meter. That means for a 60 square meter job, the cost is going to be £6,000.

Customers often exclude windows and doors from this area however, and that will probably lead to an underestimation of cost. Unfortunately it is much easier to insulate a wall with no windows, as adding in that detailing around the windows and creating a nice clean finish around the reveals takes a lot more work. As a result, we recommend measuring the whole wall from ground to gutter and end to end to come up with your square meterage.

Extension work and fixings

Usually the cost we have indicated here will cover pipe extension work and the usual fixing you have on your wall. If you have a lot of complicated fixings, or you need to get a gas appliance flue extended you could be looking at several hundred pounds in addition in order to complete those works.

Cost of materials

Materials usually don’t add much to the cost of the works – they are relatively inexpensive compared to the cost of the labour. There are some situations where materials cost will affect the price:

Type of insulation material – Rockwool is sometimes preferred by architects and builders as the material is more breathable and less messy to work with than other options. It will add 20-30% to the cost of a typical job however.

Double or Panzer Mesh – Using two layers of mesh or an extra strength ‘Panzer Mesh’ will add around 20% to the cost of the job – this is only usually used in areas where impacts on the wall are more likely to happen, like on a wall next to a public pavement.

Scaffold – Scaffold can get very pricey, and will vary from job to job. On the average semi detached property, a scaffold contractor might charge £1,500 if the job is relatively straight forward. If there are more than 2 levels or there are awkward areas with restricted access or obstacles in the way – like a conservatory for example, then the cost will increase. For an average job, Be Constructive will include this cost in the £100/m price, but more expensive scaffold jobs will add to the overall cost.

Multiple colours and detailing  – If you want to go for a very dark colour, or you want to add in detailing or extra features in multiple colours, the cost is going to go up accordingly. This should be in the hundreds rather than thousands of pounds – so not a huge factor in price.

If you want to get an accurate quote for materials, use this calculator courtesy of our friends at EWI Store – click on the picture to get started:

This should give you a good idea of the cost of the works. Of course, this is just one company’s pricing structure, and others may vary somewhat. There are slightly different systems out there, but if you are getting charged much more or much less that the price we suggest here, chances are there is something not quite right – perhaps you are getting ripped off by the installer that is charging too much, or being given a third rate job by a company at the bottom end of the market. Always get at least 3 quotes to make sure that this is not the case for your home!

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