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!
Installing solid wall insulation
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If there is a basement level digging down and having the below ground exterior wall spray closed foam cell sprayed will insulate well and help prevent ingress of dampness.
Any idea what a scaffold contractor might charger for a 3 story detached properly? I’m assuming it would be a fair bit more than the estimated £1,500.
Hi luke,
Tricky to say as it depends on some of the obstacles the scaffold will have to go over – like extensions and conservatories, as well as the access. I think you would be looking at a bit more than £1,500 though – the extra story is what is going to really take the price up. Maybe something around £3-4k would be typical.
Check your maths.
Yeh the price of the external wall insulation system is fair enough. We are about to embark on a fairly sizable project, increasing the loft space, a side return and completely re-rendering the house. Do you have a ball park on the percentages I could save if I did external wall insulation and rendering as a joint project rather than standalone. We might also do the windows. They were installed about 12 years ago, but on one or two I can see the sealant is beginning to go.
Hi Dave, where abouts does the issue lie and we can look into it?
I think dave was REFERRING to £10/sq m and a 60m sq space costing £6,000 rather than £600
Hi Julia / Dave,
Our team have made the change – sorry about that and thank you for pointing it out!
Does anyone have any idea how much internal solid wall insulation tends to cost per square meter? Lots of information on external, but can’t find anything about internal other than general estimates for certain types of houses.
Hi, I have a detached solid wall house. I have condensation issues in built in wardrobes on a NWW wall and slight condensation on the same wall outside of the wardrobes. Ventilation in the bedroom is not great as there is no vents or trickle vents and there is also an ensuite. We do open the window in the ensuite and it does have a fan. My query would be. 1. Can I have just 1 or 2 walls insulated (North and West wall. Front has several windows and West has almost none.) And how much of an effect will it have to the condensation in the built in wardrobe?
HI Jason.
It may be that the wardrobes themselves are the cause of the damp. Could they be changed for stand alone as there is no air circulation and the warm room on the cold external wall may cause this damp. Might be worth a try or leave doors open for a while to see if there ois a change.
Regards
Mark.
External insulation should mean that the inside of the outside wall within your wardrobe will be warmer than they currently are. Therefore external insulation should help.
Internal wall insulation is another matter entirely and can result in the inside of the outside wall being cooler with concomitant increase in risk of condensation.
is there a grant for underfloor insulation?
I have a 1850 solid wall detached 2 story house which is very damp internally always above 80% humidity, would external insulation help in reducing the damp and by how much approximately.
Seems unlikely: the problem is the amount of water inside your house, not the temperature. Look at your ventilation options (like MVHR) or consider installing dehumidifiers.
Seems a lot of money for insulation. I have a detached property roughly 60 sqm of 80mm PIR insulation @ £15 per sqm = £900
With larch cladding covering said 60 sqm approx £3000
Total adding in timber strapping no more the £4500
Including ;labour?