Applied exterior finishes

Provided failure is confined to the tile adhesive, tile replacement is relatively easily effected.

Failure of the rendering is more of a problem. The extent of failure can be detected by a hammer survey but this is time consuming and close access is needed.

Severe spalling of glazed finish to porous body glazed brickwork. The pattern of spalling suggests expansive forces, possibly frost or crypto efflorescence behind the glaze. Note white staining in centre of photograph.

Final initial appraisal, cradles, hydraulic platforms or abseiling techniques will need to be used. For large areas, where a fairly rapid assessment is required, thermographic surveys can help to pinpoint areas at risk provided that delamination has occurred and that a suitable temperature differential can be created.

Apart from removal and replacement, it is possible to re-bond areas of delamination using vacuum grouting techniques. (Pressure grouting only forces the finish further away). Specialist firms undertake this work, however, care in the selection of resin adhesives is vital. Some early epoxy resins tended to absorb water and expand on wetting, perpetuating the problem that it was hoped to address. Some controversy remains as to the effectiveness of vacuum grouting.

Cracks in finishes can be grouted but care must be taken to determine the reason for cracking and to select a rigid or flexible sealing system as appropriate. The bonding of a reversible movement crack will only induce further cracking elsewhere.

Where the substrate has failed, particularly where sulphate attack is the cause, the affected area will almost certainly need to be reconstructed.

In extreme cases the use of overcladding may be desirable provided the existing finishes are removed, stabilised or restrained before installation of the new cladding system. An alternative method may be to use a stainless steel render carrier and reinforced render system.