As with any refurbishment of a system built property the correct structural checks and examinations should be undertaken prior to the application of the external wall insulation system. Once established as a suitable property for and EWI application then the over cladding can proceed. On the main areas where the concrete panels occur, a fixing pull out test should be undertaken to establish the correct fixing type and length for the system being applied.

Using an adhesive and mechanical fixing application, apply the insulation boards to the walls ready to be beaded and base coated. Once applied the insulation boards are ready to receive the basecoat and depending on the system the correct profiles and beads to suit the finish to be applied. The area at the gable apex is vertical clay hanging tiles onto a timber frame background.


Remove the tiles and battens back to the timber frame which should then be inspected and any failing timbers replaced. To meet the requirements of the u value the timber frame will need to be infilled with a mineral wool type insulation as a contribution to the overall calculation.

Once completed an external grade sheathing board is applied past the front face of the concrete façade where there will be a surface expansion joint situated to allow for differential movement.

The structure comprises of precast reinforced concrete columns at 915mm centres. The frame is lined to both sides with precast concrete slabs. Internally plaster finished but external faces are generally untreated. This type of construction utilizing a pressed metal ring beam at floor level and eaves meant that design was extremely flexible and could be used to provide small blocks of apartments over three storeys.

This method of construction proved to be very popular and over 19000 Unity Houses were constructed.

Problems were encountered at the floor slab, which was found to be delaminating at the edges and presenting a very uneven surface. In order to seal this detail, and further reduce cold bridging, a 30mm thick layer of insulating render was laid between the back of the base bead and the blockwork. The installed system achieved a new "U" value of 0.33 W/m2K.

Potential Problems

In general Unity Houses tend to stand up very well to the rigours of the British Climate and as such

it is generally the case that they are structurally sound. However, there are cases where the copper ties that bond the facing precast panels to the framework have corroded. Therefore, it is essential that investigative testing is carried out to ensure that any problems are exposed and necessary remedial action taken prior to the undertaking of any external cladding works.


Improved High thermal targets can be achieved from 0.30 U value onwards using the different insulation types and thicknesses as be determined by the specification requirements.

System Components - Options to suit specification requirements

  • Lambdatherm Grey EPS Insulation Boards
  • White EPS Insulation Boards
  • Phenolic Insulation Boards
  • Rockwool Insulation Boards
  • Insulation Adhesive
  • Insulation Fixings
  • Basecoat
  • Reinforcing Mesh

Topcoat Finishes to select from

  • Dash aggregate
  • Silicone/Acrylic Topcoat
  • Envirobrick "brick effect" Render
  • Granomin + Nanosil Finish Topcoat
  • Brick Slip Systems
  • Colour samples are available on request for the different finishes

For a full technical consultation, survey and project specific report and specification please contact our technical department on 0845 1300 983 or email at info@spsenvirowall.co.uk