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Stucco repair and restoration

Common stucco – exterior render prepared from hydraulic lime, sand & hair

Stucco is build up from 3 layers Construction

Three types of stucco render

A fat lime & sand and cement sometimes with animal hair as reinforcement, a hydraulic mix containing either hydraulic lime and sand, or fat lime with a pozzolanic additive and sand.

Correct identification of the material used is essential when carrying out repairs to ensure both historical continuity and structural compatibility, as a different mortar mix may well be imcompatible with the original.

Common problems with Stucco

The most common reason for failure is neglect. Whiles stucco is a durable material, regular maintenance is required to prevent excessive water penetration and a breakdown of the surface. Blocked or damaged gutters which often leads to salt efflorence, staining and biological growth. Excessive water penetration is liable to cause loss of adhesion causing bulging. Trapped water may also freeze and expand causing possible strucurall damage.

Solution

Stucco is fairly easy to repair. Crack greater than 2mm in a lime based stucco should be carfully cut out, flushed with water and replaced with the same base material. Hollow areas and voids should removed and also flushed out.

Salt efflorencence may be dry brushed and removed from the surface, as should all algal growth. A suitable biocide should be applied to affected areas only to ensure no further growth.

Substituting modern materials from the original should always be avoided if at all possible.

Permashield wall coatings can be applied to give maxium protecting.