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External wall insulation installation process

Updated: Jul 15, 2022

If your property was built before the 1930’s the likelihood is that your property will have solid walls. If you are unsure of your property’s wall type, have a look at our blog What is solid wall insulation?

If your home has solid walls, or you are unable to fill the cavity with insulation, you would need to insulate either internally or externally.

An external wall insulation system is a thermally insulated, protective, decorative exterior cladding procedure involving the use of expanded polystyrene, mineral wool, polyurethane foam or phenolic foam, topped off with a reinforced cement based, mineral or synthetic finish and plaster.

External wall insulation installations can be complex and should be undertaken by a professional, as it will transform the appearance of your property and in some cases, planning permission may be required.

Adding external wall insulation (EWI) to your house is an effective way to reduce the amount of energy needed to heat your home, saving you money on energy bills as well as lowering your carbon footprint. With the UK aiming to reduce its carbon emissions by 80% by the year 2050, insulating your property brings you a step closer to living in a carbon neutral home.

As mentioned before, the process of installing external wall insulation can be quite complicated so best left to the professionals. We’ve outlined some of the basic steps of the installation process to for your reference.

Render test

Before any works commence, the render is tested to see if it is strong enough to support the new insulation or whether it needs to be removed. If the render is strong enough, it will be smoothed over before the new insulation is applied. If not, the render will be removed to provide a solid base.

Remove and adjust pipework

Once the render has been smoothed or removed appropriately, the pipework must be removed from the installation area to ensure there is complete and clear access. Temporary down-pipes may be installed to ensure the water runs down the side of the property. Any waste pipes or soil pipes may have to be removed or extended away from the walls to allow the building to function normally during the installation process.

Window protection

Your windows may be fitted with a protective layer to prevent them from being damaged. This is also a good time to consider replacing your windows if you are thinking about replacing them in the near future. Replacing your windows during the external wall installation process may also save you some money and additional disruption later.

Installing insulation boards

Insulation boards will be applied to the walls once a starter track has been installed to create a level starting point. A layer of adhesive is used on each board to stick onto the wall in a staggered pattern. Boards are cut to size and shape to fit around windows and other obstacles. Once all the boards have been installed, a file is used to smooth down the edges to ensure the finished surface is completely flat.

Mechanical fixings

Mechanical fixings are used in conjunction with adhesive to make sure the insulation boards are fixed securely. Approximately 10 fixings per square meter are hammered into the boards to ensure they are not blown off or damaged during bad weather.

Adding beading and render

Beading is used to make sure the insulation remains secure and tight around windows, doors and any other obstructions. Beading helps to create neat and tight edging and prevents insulation from touching other materials.

A strengthened render is then applied to the boards with a fiberglass mesh in between once the beading has been fitted.

Applying primer

The primer is painted on once the strengthened render and reinforced mesh has been installed. The primer usually contains granules to allow the final coat of render to stick to it. The primer is also usually colour matched to the final render to make sure the finial finish is a solid colour.

Applying the final render

The final coat of render is the most important in the decision-making process as it is what’s going to be on view, so make sure you choose the exact colour and texture you like.

Reinstalling pipework

Once the render has set, any pipework or fixtures which may have been removed can be reinstalled. Your window sills may need to be made deeper to allow for thicker walls. Sills can be extended by using window sill extenders or by adding new wider sills on top. In some cases, you may also require new or extended verge trims where the roof meets the wall as the wall has been widened.

Find out more about How to find your local installer or have a read about the other ways to help Reduce heat loss in your home with a few handy hints and quick wins.

Why not take a look at the other insulation measures ESW Insulation have to offer:

ESW Insulation also offer a stand alone rendering service to renew or upgrade your current render or finish. Questions? Call the ESW Insulation Team on 0117 955 9333 or contact us here.

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