week 27: external wall insulation

External wall insulation

Having been delivered some 6 weeks ago (see earlier post), the external wall insulation is now starting to go on. Starting with the extension late last week, but in earnest this week to (almost) complete some 80m² of wall area. The main (original) house is left to do, it should be done in approximately 3 weeks time if we manage to keep this pace up.

We are using two layers of Kingspan K5 insulation boards. These are 60mm thick giving a total of 120mm external insulation. The first board gets bonded to the wall using Knauf Marmorit SM700. After this has gone off, the second insulation layer is applied with the boards offset in order to cover any air gaps between boards in the first layer. This second layer is mechanically fixed using thermally-broken fixings through both boards and into the masonry.

EWI - new kitchen  EWI - side wall

The wall insulation will eventually be finished with a mix of through-colour render and splayed chestnut timber cladding. In the meantime the house will look like a marshmallow!

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2 thoughts on “week 27: external wall insulation

  1. Do you have any photos of the interface between the K5 EWB and the original wall? I am planning similar and am considering whether to do a smooth base render/slurry coat to mine befor the EWI goes on.
    In these windy times it gets me thinking it should have a smooth surface to back onto.

    Were the EWB boards dot and dab as well?

    • I do have lots of pictures at different stages, so will do a short entry with these soon. I would recommend that you do a slurry coat, but this does depend where you intend to put your air barrier. The key thing is to ensure that there a no air gaps behind your insulation panels. This can be done using a comb applied, or dab applied adhesive as needed to build up to take out any undulation.

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