Guide to Insulating: How to Prepare for Solid Wall Insulation

What is a ‘Solid Wall’?

It might seem like an obvious question to ask – I think we can all agree that walls should always be solid and structurally sound, especially when it comes to building and construction. However in this context, a ‘solid wall’ refers to the way a walls’ brickwork is laid out during the building process. 

In short, a ‘solid wall’ is an external wall of a building which has no cavity or gaps. If a wall does have a cavity space or a gap, this is called a ‘cavity wall’. A cavity wall will have an external layer of brickwork, then a gap, and finally, it will have an internal layer of brickwork.

Before you can begin your building or renovation project, there are 3 key questions that you should ask yourself: 

Solid Walls or Cavity Walls: Which is Which?

1. Does your Property Have a ‘Solid wall’ or a ‘Cavity Wall’?

There are a few ways to help you figure out if your wall is a solid or cavity wall. The general rule is that if your property was built before the 1920s, then it is likely to have solid walls. If it was built after this period, then it is likely to have cavity walls. Finding out how old your property is can help you figure out which type of wall you’re working with. 

Another method you can use is check the external brickwork (if it hasn’t already been covered over). If the bricks on the outside of your property are showing their longest side, then you probably have a cavity wall. If you can see a mix of long and short sides, then you’re dealing with a solid wall.

If you’re still not certain, then it’s time to break out the measuring tape. Open an external door or a window of the property and measure the thickness of your walls. If the wall is less than 260mm thick, then it’s likely a solid wall. If it’s more than 260mm thick, the extra thickness is probably due to a gap between brickwork, in other words, a cavity wall.

Solid wall Vs Cavity Wall


2.Is the Property Already Insulated?

Another thing to consider is if your property already has insulation in place. This can be a great indicator to help you determine which kind of wall you're working with. For example, if your property has solid walls, then there’s a good chance that they won’t be insulated.

Alternatively, If you have cavity walls and your home was built from the 1990s onwards, then you probably have cavity wall insulation in place. However, homes with cavity walls built before this period usually don’t have any insulation.

It’s important to remember that adding insulation is a job that could have been implemented by a previous owner, so don;t forget to refer back to work that’s been done on the property in the past to make sure.  


  1. Why Do You Need Solid Wall Insulation?

Our homes are our castles, and like any castle, they’re supposed to protect you. While there are a few things you can do to make your property more secure, adding solid wall insulation can provide extra protection in a variety of ways. 

Adding insulation to your property can help create a thermal guard that can reduce the loss of heat in the winter and keep the cool in during the summer months. It can also provide acoustic insulation from noises from the outside world and protect the structure from damp and mould problems. 

In other words, insulation can save you money on your heating bills, make your home more eco-friendly, create a peaceful and relaxing space reduce the risk of damage to your home and reduce the risk of illness caused by mould.

Solid wall insulation Savings

How to Insulate A Solid Wall 

If you have cavity walls, you could choose to get the gap filled in by a firm specialising in that type of insulation, however this type of insulation is not as effective as the type of insulation used in solid wall insulation projects. As stated by the Energy Saving Trust – who help people to make better energy choices – insulating a solid wall “will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too.”

If you have a solid wall, this can be insulated either from the inside or the outside. If you choose to insulate from the outside, this will generally cost more than insulating from the inside, but does mean that you don’t lose any floor space in the process and will not have home-life disrupted while the work is being undertaken.

It’s nice to sit back and let a professional get on with everything, but paying for labour greatly increases the cost of any project. So, if you want to save money on the cost of the work, it’s DIY time. With careful research and the right materials and tools, you can achieve just as good a finish as a tradesperson would.

Step 1: Check Building Regulations

When it comes to building and construction work, checking building regulations should always be top priority; but it's surprising how often it’s ignored or forgotten. Neglecting to make the appropriate checks can often end up with a project being pulled down even when it’s finished because it isn’t up to code.  

So before you start, check with a building control body to see if any building regulations apply to the work you are planning. When it comes to insulation UK homes must meet minimum energy efficiency values, so make sure you take this into account during the planning process, otherwise it could cost you in the long run. 

Step 2: Find the Cost of Wall Insulation

Solid walls can be insulated either from the inside or the outside and on the route you choose can have an impact on the cost of your project. On the one hand insulating from the outside can cost more, but it does mean that you won’t lose any floor space in the process. On the other hand, insulating your property from the inside is more cost effective, but it does mean you might need to sacrifice some space to make it happen. 

Typical installation costs (Based on a typical semi-detached house in Great Britain) of solid wall insulation can vary as follows:

  1. External wall insulation: around £13,000
  2. Internal wall insulation: around £7,400

It’s also important to remember that there are different types of insulation, and different products can offer additional benefits depending on what you need. Don’t forget to shop around to find the best kind of solid wall insulation for your solid wall project and factor this in during the early planning stages to avoid any unforeseen costs.  

Step 3: Choose How to Insulate Your Solid Wall

There are two main ways you could choose to install your solid wall insulation. Solid walls can be insulated internally by fitting rigid boards to the wall. Rigid insulation boards are incredibly thermal efficient and can reduce the number of battens or studs required for the project. They’re normally fixed to the wall using a form of plastic or adhesive, and can be adapted to walls that are weathered and uneven for a secure fit. 

Alternatively, you could use stud walls. Stud walls are made of metal or wooden frames and are placed parallel to the wall to create a space where insulation material like mineral wool fibre or multifoil can be placed. Once the space has been filled, the new wall is plastered, making it ready for decoration. 

Step 4: Prepare the Right Tools

As with any building project, make sure you have all the tools you need before you start your project. Tools you will need include:

It’s also important to make sure you have the right personal protective equipment for the job. When it comes to insulation, Safety goggles, gloves and a mask or respirator are crucial because tiny glass fibers can irritate your eyes and lungs, which can have a significant impact on your health if handled incorrectly. You’ll also want to protect your property, so dust sheets and  kneeling boards are options that are worth investing in. 

Step 5: Set Extra Time Aside

Adding insulation to a solid wall isn’t a quick job, especially if you want it done right. As a result, make sure you set enough time aside for the project. 

If you can, take some time off work to get the job done at a sensible pace, with enough time to rectify any issues you weren’t expecting, such as needing a couple more panels of plasterboard. If you can’t take time off to complete the job in one go, think about good points during the project at which you can down tools until you have time to continue.

Types of Solid Wall Insulation

Typically there are three varieties, boards, slabs, and rolls that you can choose for your project. If you're eco-minded, there are also a range of natural insulation options if you want your project to have greener credentials. Each one is useful for different projects and build situations; boards and slabs are a great choice if you want to save space, while rolls are great for acoustics and lowering energy costs.

These three varieties of insulation material can then be broken down into 4 categories – acoustic, thermal, fireproofing and condensation resistant. 

Acoustic insulation - As its name suggests, acoustic insulation is a great choice for soundproofing rooms where noise reduction is a priority. It can also work both ways, helping to reduce noise from the outside as well as between rooms, making it a perfect choice for bedrooms as well as home offices and garage spaces. 

Thermal insulation - The main goal of thermal insulation is to prevent heat transfer in your property. This means that during winter months, thermal insulation prevents heat from escaping through the walls. In the summer months, it’ll also prevent exterior heat from permeating your walls, which can help keep your property nice and cool. 


Fireproof insulation – Fireproof insulation has two key properties that make them an effective choice when it comes to fire safety. To start, it's effective at preventing certain types of fires such as electrical fires from starting. It's also specially designed to resist high temperatures, to contain fires and to stop them from spreading, which can give occupants enough time to escape and emergency services an advantage when dealing with the fire itself. 

Condensation resistant insulation – Condensation occurs when a surface is colder than the water vapour. For many homes, it can become a problem if there is a high moisture content in the air and poor ventilation, which can cause damp and mould to develop.  Condensation resistant insulation is not only made of materials which stops these issues from developing, it also reduces the temperature differences which adds an extra layer of protection. 

The Benefits of Solid Wall Insulation

Thermal guard 

Solid wall insulation protects your home from the cold air and moisture and traps heat where you want it to be. Good insulation means a warmer home in winter and a cooler home in summer, making day to day life more comfortable in the process!

Cost saving

When you have an uninsulated house, a lot of the heating you’re paying for disappears into the outside world, meaning you inevitably spend more money maintaining a comfortable home than you should need to. Insulate your home and see your heating bills go down. Money saved!

Reducing your carbon footprint

The more energy you use to heat your home, the more fuel you’re using, which can significantly increase your home's impact on the environment. By making your home more energy efficient you’ll be able to reduce your carbon footprint and save money in the long run. Why not save the world from the comfort of your sofa!

Long-lasting comfort

Solid wall insulation will last for decades, so you can rest easy knowing that your home is well protected from draughts and damp, and your savings on heating bills will keep piling up for a long time. Ultimately it's not just money well spent – it’s also money well saved!

We have a great range of insulation products available for every project and every pocket. Why not head over and browse the full range. If you need any help, then why not have a chat with our team? They’re always on hand through live chat, or give us a call on 020 3481 1978.

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