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Last updated on May 11th, 2022

How much does external wall insulation cost?

If you’re keen to reduce your energy bills, insulating your external walls could be just what you need. But unlike insulating internal walls, external wall insulation can be more complex and costly – especially if we assume that your walls are solid. Use our guide below to calculate how much you can expect to pay.

How much does external wall insulation cost?

The cost of external wall insulation depends on a number of factors, including:

Cost provided itemCost+VAT
(Lower range)
(Higher range)
Average cost

Our costs are ballpark averages – get a local tradesperson to quote now

1. Whether you have solid walls

Cavity walls are common in houses that were built post-1920. These are generally quick and easy to insulate, with the typical semi-detached house costing around £475 to insulate.

On the other hand, most houses built pre-1920 have solid walls, which let twice as much heat escape. That’s around a third of homes in the UK! Sadly, solid wall insulation is much more expensive so this is what we’ll be focusing on here.

2. Whether you insulate your external walls internally or externally

We know that it can seem confusing to use the word ‘external’ in two different ways. But the truth is that solid walls can be insulated either internally or externally.

Insulating externally involves fixing a layer of insulation to the outside of your wall using mechanical fixings and adhesive, before covering it with protective layers of render or cladding. You can save money by insulating internally, but this does reduce the size of a room by bringing in the wall by around four inches.

3. Whether you need scaffolding

External solid wall insulation often requires scaffolding, so this is an expense you’ll need to factor in – unless you’re lucky enough to live in a bungalow!

The cost for a single scaffold up to 10m high is about £625 per week.

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External wall insulation cost per m2

External wall insulation being added to houseThe cost of external wall insulation is usually around £100 per square metre, so it can range from £8,000 for a small flat to £22,000 for a large detached house. This figure includes scaffolding, but it’s worth noting that if more than two levels of scaffolding are required or there are obstacles like conservatories in the way, the cost is likely to rise.

How to save on the cost of external wall insulation

Solid wall insulation isn’t a cheap undertaking, but there are a few ways that you can save on the cost:

  • Schedule the work at the same time as other building works, to maximise on your use of scaffolding.
  • Check if there are any local council grants available.
  • Also speak to your energy supplier to see if you qualify for any grants.
  • Check if there are companies willing to offer you finance.

You may consider taking on the work yourself to save money. If you’re very experienced at DIY, you may be able to get away with insulating your solid walls internally, but external solid wall insulation should only be fitted by a trained installer. Use our free search feature to find a specialist near you.

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External wall insulation cost calculator

When calculating the cost of insulating the exterior of your home, the area of your walls is a key factor, and you can expect to pay around £100 per square metre. Beyond this, you’ll need to factor in the cost of adjusting fixtures and fittings that sit on the wall, such as drain pipes and boiler flues. Most accurate quotes from a professional will include this.

Finally, you’ll need to consider the cost of the materials needed to do the job. Larger walls will need more insulation, more paint and more detail to create if you want a certain type of finish. There are also options when it comes to the actual insulation material, with some offering greater insulation and strength at a greater cost.

External wall insulation installer hourly rates

As mentioned above, you’ll find external wall insulation specialists charge per square metre, not per hour, as the focus is on completing the job, not working a number of hours. Plus, unlike fitting a plug socket, for example, where it’s mostly the professional’s time you’re paying for, with external wall insulation there are considerable material and equipment costs that make up your quote, not just the hours spent on site.

So, instead of the hourly rate, it’s the price you’ll pay per metre squared you need to consider, and this will vary depending on where your property is in the UK, with London and the South East being considerably more expensive.

External wall insulation quotes

When pricing your external wall insulation job, it’s important to get a number of quotes from different local professionals in order to pay a price you’re completely comfortable with. It is also a good idea to check with installers that your installation will be covered by an appropriate 25-year guarantee if they are members of the SWIGA guarantee scheme.

Thankfully, it’s easy to get multiple quotes from recommended insulation specialists near you – simply enter your postcode in the free search tool below to get started.

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FAQs about external wall insulation

What’s the difference between solid wall and cavity wall insulation?

The main differences between solid wall and cavity wall insulation are the way in which insulation is installed, and the cost. Solid wall insulation is more than likely what you’ll need if your property was built before 1920. It involves adding insulation to either the exterior of your property on the outside walls, or to the interior on your room’s walls.

Cavity wall insulation is the easier and cheaper method of insulating your property and is typically the approach on houses built after 1920. This method involves filling the cavity between the two layers of bricks that make up your outside walls. Take a look at our cavity wall insulation cost guide for a more detailed breakdown of average costs.


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Very usefull, well defined thanks


Amazing Write-up. Thank you!

Loft Boarding Specialist

This is great. Thank you for sharing your knowledge with us. I can't wait to read more from you!

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