BS 8481:2006 pdf download
BS 8481:2006 pdf download.Design, preparation and application of internal
gypsum, cement, cement and lime plastering systems一Specification.
3.2.3 plastering system
pla.ster coat or sequence of plaster coats applied to a background, including the possible U$4? of a port and/or reinrorcement ant’or pre-treatment
3.2.4 otw-eoat plaster
plaster applied In one-coat which fuLfils all the functions of a plastering system
3.2.5 muLti-coat plaster
l)laster system iLsing a sequence of plaster coats to achieve the required tliivkticss wtit-n all operations are completed after the plaster has set but not dry
3.2.6 undercoat
lower plaster coal or plaster coats of a plastering sysleni
3.2.7 finalcoat
last plaster coat of a multi-coat plastering system
3.2.8 dubbing out
process of large localized irregularities in the background, such as hollows, prior to the application of an undercoat
3.3 Background definitions
3.3.1 background
surface of a construction element to which a plastering system Is to be applied
3.3.2 key
roughness of a surface which enables plaster to make a bond
3.3.3 support
product attached to the background to which a plaster is applied so that (1w i,Iastenng system is largely indeiflcIcflt of 11w background (e.g. lathing)
3.3.4 reInforcement
material Incorporated within a plaster coat to Improve resistance to cracking (e.g. mesh)
3.3.5 bonding agent
proprietary material used to provide adhesion of the plastering system to the background where iweessary
An assessment shall be undertaken to determine compatibility between the gypsum plastering and the background. As a minimum the assessment of the background shall include the following checklist.
a) Does the background provide adequate support: strength, rigidity and adequate key and suction for the adhesion of the gypsum plaster?
b) Is masonry fit for purpose?
c) Are boards, slabs and polystyrene fixed securely plastered only when they are dry and dimensionally stable’?
(I) Has background movement including structural, moisture and thermal movements been minimized?
e) Have defects in the background, e.g. lack of adequate key, weakness, contamination been minimized?
f Is there adequate suction control?
g) Has efflorescence been minimized?
NOTE Such compatibility is necessary to avoid bond failure between successive coats or between the first gypsum plaster coat and the background.
If any of these inadequate characteristics of the background exist, then other means of providing support and/or additional adhesion shall be used (see Annex A).
Where the background conditions are such that there is a high and/or variable suction a pre-treatment incorporating a primer agent such as a bonding agent shall be used.
Where background conditions are such that there is low key and suction a pre-treatment incorporating a bonding agent shall be used.
6 Characteristics of gypsum plastering systems
The designer shall undertake a design assessment of all the functional and aesthetic aspects of the building detailed in 5.2 a) to e) except that this is for cement, and cement and lime plasters rather than for gypsum plasters.
7.3 Background
The background commentary, recommendations and requirements of gypsum based plastering systems (see 5.3) shall also apply to cement, cement and lime plaster systems.
8 Characteristics of cement, cement and lime plastering systems
8.1 General
8.1.1 Cement, cement and lime plasters
COMMENTARY ON 8.1.1
Cement, cement and lime plasters have a cont rolled, set. During the th7Jing out process, shrinkage might take place depending on the materials of the plaster mix. Gement, cement mid lime plasters C(Zfl be decorated with most proprietary fjnishes u.’hen dry.
The appropriate cement, cement and lime plaster can be used inmost areas. Plasters for special designed requirements are described in BS EN 998-1.
