The acceptability of the wall and ceiling plastered finish can be a significant item in the snagging procedure. Selection of appropriate materials and techniques may not always be thorough, particularly with respect to shrinkage of backing coats and resultant cracking, and detachment of surfaces. Rigorous design procedures and quality control on site are therefore of major importance in reducing, if not eliminating, defects. This Good Building Guide addresses these issues, drawing primarily from the experience of BRE site investigations.
This Good Building Guide deals exclusively with
plastering on new construction. However, some of the techniques described in Good Building Guide 7 on "Replacing failed plasterwork" (eg matching the system to the background) also apply to this Good Building Guide, and the gist of those recommendations is therefore repeated here.
This Good Building Guide does NOT deal with:
● plasterboard fixing and finishing,
● gypsum mortars, or
● plastering techniques appropriate to the restoration of heritage buildings, including:
- the use of exclusively lime-based formulations,
- scaglioli work,
- the addition of animal hair as reinforcement,
- plastering on laths,
- the running of cornices in wet plaster using wood or metal profiles, and
- the casting of decorative plaques in fibrous plaster or other surface modelling such as pargetting.
Part 1 describes the commonest types of gypsum and cement-based plasters available, the selection of suitable plastering specifications, whether for skim coat, two-coat or three-coat work, in relation to the substrate material of wall or ceiling, the protection of abutments, avoidance of potential loss of adhesion, and thermal and moisture movements of the most common backgrounds and plasters. 8 pages.
Workmanship, including permissible deviations of the finished surfaces, is dealt with in Part 2.