Anomalies in Wall Renders: Overview of the Main Causes of Degradation

Abstract

The assessment of historical buildings is usually focused on: 1) structural features related to brick or stone walls, wooden floors and other structural elements, or 2) highly valued decorative features, such as frescoes, stuccos, and facade details. During the last quarter of the 20th century, some "secondary" elements also started to receive their share of attention from researchers and practitioners. Wall renders are one of the most important of such elements because of their role as a sacrificial protective layer and the numerous problems that were encountered in the past as a result of incompatibility issues in rehabilitation works. This article discusses the main causes of the deterioration of wall renders, with emphasis on lime-based renders; these renders thoroughly reviewed and their relative weight in the overall degradation is addressed.

20th-Century Award-Winning Buildings in Lisbon (Portugal). Study of Plasters, Rendering, and Concrete Materials Aiming Their Sustainable Preservation

“…As shown in Table 7 and in Figure 5, in situ tests to evaluate the moisture content revealed "wet" to "very wet" zones for all PRCBs assessed. Infiltration, capillary rising water, and moisture stains are the main anomalies related to water and are present in almost all PRCBs evaluated, which is in accordance with the main problems affecting old masonry structures (e.g., [50,[62][63][64]). The water-related anomalies in buildings CVT (1903), AR49 (1923), CBP (1939), and AAC (1944), point out different sources of water.…”

“…Amongst other degradation causes, salts crystallisation (efflorescences and cryptoflorescences), pollution, water, and biological activity, structural defor-mations, and dimensional variations due to shrinkage or thermal actions can be recognised [49]. External agents, application technology, mixture composition, aggregates and binder type, porous structure, water to binder ratio, and curing period are among the factors that may influence mortars and concrete performance [50].…”

Assessment of test methods for the durability of thermal mortars exposure to freezing

“…On the other hand, knowing that the larger the pores, the lower the crystallisation pressure, the higher pores dimension of lime-based mortars contributes to less mechanical degradation. This fact is due to the formation of crystals inside the pores not producing excessive pressure [22]. However, the degradation of lime-based mortars and masonry materials due to salt crystallisation is an important issue, especially in historical buildings [23][24][25][26].…”

Geophysical and geochemical techniques to assess the origin of rising damp of a Roman building (Ostia Antica archaeological site)

“…Both, among others, represent one of most harmful problems of historical building in archaeological site, particularly exposed to aggressive environmental conditions. In fact, water, coming from the rain (infiltration) or by capillary rising damp is the cause of several decaying processes for porous materials [19][20][21][22]. Thus, methodologies based on the use of naturally occurring isotopes have a large spectrum of applications for hydrological problems encountered in water resources research [23].…”