How to fit an electrical socket to insulated plasterboard

Increasing the levels of insulation in a property is an effective way of reducing fuel bills and a common method of doing this is by adding insulated plasterboard to the internal walls.

However this works best when there is a continuous layer of insulation all around the property – something that is not always possible when electrical sockets are added to the walls. If these are not fitted correctly then heat will be lost through where the socket penetrates the insulation.

In this post we look at the best methods of fitting an electrical socket to insulated plasterboard in order to prevent heat loss. Please note that only qualified electricians are allowed to work with electrics. This blog post only looks at fixing the sockets boxes.

By fitting an electrical socket in a wall covered in insulated plasterboard means breaking into a continuous layer of insulation which can cause linear thermal bridging; additional heat loss at junctions between elements and around openings in elements as well as uncontrolled air leakage via the penetrations.


Consider the best place to locate your services.

The simplest and most effective solution will be to put the electrical sockets on a wall which is not covered in insulated plasterboard, such as an internal wall. This means that there would be no necessity to penetrate the insulated plasterboard, maintaining the continuous layer of insulation and reducing the risks of condensation, heat losses via air leakage and thermal bridging.

This may not always be possible so if you do have to fit a socket on a wall with insulated plasterboard then the following procedure should be used. ‘First fix’ services should be installed before dry lining. There are two different types of sockets which can be fitted.

Surface Mounted Sockets

Draw round the mounting box on the insulated plasterboard. Make sure that it is horizontal by using a spirit level.

Create hole in the insulated plasterboard for wiring to run through – this can either be core drilled or cut with a pad saw. Check that there is enough cable to run through into the socket box. Make sure all the holes in the insulated plasterboard are sealed by applying flexible sealant to the penetration and the edges of the socket box and fix unit into place with dry-lining anchor fixings.

Recessed Sockets

socketFor recessed sockets we suggest you install proprietary plastic switch and socket boxes which should be clipped directly to the plasterboard. This eliminates the need for backing noggins. They should, however, be backed by a sufficient level of flexible insulation as the insulation component of the insulated plasterboard is being removed.

When you have decided where the socket is going, draw around the mounting box ensuring that it is horizontal with a spirit level. Use a sharp knife or pad saw to cut an accurate hole in the insulated plasterboard.

Flexible insulation can then be either adhesively bonded or fitted behind the socket box, depending on the type of insulated plasterboard used.

  • If using Kingspan Kooltherm K14/K18 Insulated Plasterboard the flexible insulation should be placed between the timber battens (before fitting the insulated plasterboard) where the socket is to be fitted.
  • If using Kingspan Kooltherm K13/K17 Insulated Plasterboard the flexible insulation should be inserted into the hole which has been cut for the socket and fit it in place. A continuous ribbon of adhesive in a box shape where the socket is to go will help keep the flexible insulation in place.

For airtightness add sealant around the perimeter of the socket box and either add more sealant where the cable enters or use a proprietary grommet. Alternatively a self-adhesive pad can be inserted to the rear of the back box or as a liner to the inside of the back box.

When the socket box has been fitted the socket can be wired up by a competent electrician.

There are more details and a training course for Internal Wall Insulation which includes details of socket installation.

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Kingspan Insulation is a market leading manufacturer of optimum, premium and high performance rigid insulation products and insulated systems for building fabric and building services applications.

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