It’s obvious that an assessment of the stucco should be undertaken to determine the extent of the damage, and how much of the material must be replaced or repaired before beginning any stucco repair works. Check-ups and testing should be carried out regularly all over the building to assess the overall condition of the stucco. Most stucco deteriorations are the result of water penetration into the building structure, either through the roof, window and door openings, and etc. Water causes wood lath to rot, and metal lath and nails to rust, which eventually will result in stucco to lose its bond and pull away from its substrate. The list of potential causes of deterioration can also include: ground or door frame settlement, inadequate or leaking gutters, intrusive vegetation, moisture migration, vapor drive problems caused by bathroom and kitchen vents and etc.

When the cause of deterioration has been identified, all necessary mending works of the building should be made before starting the stucco repair. Such work is likely to include repairs intended to keep excessive water away from the stucco, improving drainage and redirecting rainwater runoff and splash-back away from the building. Tops of parapet walls or chimneys are particularly vulnerable to water penetration and might require modifications to correct the problem. Besides, previous repairs carried out inexpertly and inconsistently may end up in additional deterioration and consequently in stucco removal. Incompatible stucco repair projects, external vibration caused by either traffic or construction, or building settlement can also lead to cracks which permit the entrance of water and cause the stucco to fail.

However, complete replacement of the historic stucco with new stucco will probably be necessary only in cases of extreme deterioration, for example, a loss of bond on over 40% of the stucco surface. Previous incompatible and ill-conceived repairs that compromise physical and visual integrity of the historic stucco might be another reason for total stucco removal. After all stucco removal works have been finalized there is more flexibility in choosing a suitable mix for the replacement. Since compatibility of old and new stucco will not be an issue, the most important factors to consider are durability, color, texture and finish. Generally, the best principle to follow whether for repair or replacement of historic stucco is that the stucco mix should be somewhat weaker than the masonry to which it is to be applied in order to avoid substrate damage.