SIST-TP CEN/TR 15125:2005

SLOVENSKI STANDARD
01-september-2005
1DþUWRYDQMHSULSUDYDLQXSRUDEDQRWUDQMLKFHPHQWQLKLQDOLDSQHQLKRPHWRY
Design, preparation and application of internal cement and/or lime plastering systems
Planung, Zubereitung und Ausführung von Kalk-, Zement- und Kalkzement-
Innenputzsystemen
Ta slovenski standard je istoveten z: CEN/TR 15125:2005
ICS:
91.100.10 Cement. Mavec. Apno. Malta Cement. Gypsum. Lime.
Mortar
91.180 1RWUDQMD]DNOMXþQDGHOD Interior finishing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 15125
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
June 2005
ICS 91.100.10; 91.180
English version
Design, preparation and application of internal cement and/or
lime plastering systems
Planung, Zubereitung und Ausführung von Kalk-, Zement-
und Kalkzement-Innenputzsystemen
This Technical Report was approved by CEN on 13 May 2005. It has been drawn up by the Technical Committee CEN/TC 125.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15125:2005: E
worldwide for CEN national Members.

Contents
Page
Foreword. 3
1 Scope. 4
2 Normative references. 4
3 Terms and definitions . 4
4 Materials and accessories . 6

5 Design – factors influencing the selection of cement and/or lime plastering
systems . 8
6 Characteristics of cement and/or lime plastering systems. 10
7 Types and standards of plaster finish . 17
8 Backgrounds, including preparation .18
9 Preparation and application of cement and/or lime plasters . 23
10 Maintenance and repair (other than restoration of old and historic buildings). 24
11 Specific recommendations relating to plasters containing cement and/or lime as
the principal binder . 26
Annex A (informative) Fixing applied backgrounds . 28
Annex B (informative) Restoration of plasters on old and historic buildings . 31
Bibliography . 35

Foreword
This document (CEN/TR 15125:2005) has been prepared by Technical Committee CEN/TC 125
"Masonry", the secretariat of which is held by BSI.
This document has been initially prepared by the European section of International Union of
Contractors of Plastering, Dry Lining, Stucco and Related Activities (UIEP) at the request of the
CEN Technical Sector Board (Resolution No.BTS1/56/1991). It has been revised by
CEN/TC125/JWG5 in conjunction with CEN/TC 241.
It is not the function of this document to assign responsibility for the design and application of any
work or actions mentioned within to any specific party. Such responsibility is a matter for other
documentation associated with the work, e.g. the contract.
It has been assumed in the drafting of this document that the application of its provisions is entrusted
to appropriately qualified and experienced people, for whose guidance it has been prepared.
This TR should be read in conjunction with EN 13914-2.
The following similar Technical Reports are also available:-
CEN/TR 15123:2005 Design, preparation and application of internal polymer plastering systems
CEN/TR 15124:2005 Design, preparation and application of internal gypsum plastering systems.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this Technical Report: Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

1 Scope
This document concerns the design, preparation and application of internal plaster and plastering
systems based on cement and/or lime for internal plastering on all types of background used under
normal conditions. It includes plastering onto both new and old backgrounds and the maintenance
and repair of existing work. It concerns materials, backgrounds, preparation of the surface to be
plastered, choice of suitable cement and/or lime plastering system, methods of application and
inspection and testing of plastering.
Cement and/or lime plastering mixes with special properties intended to enhance thermal insulation,
fire resistance, acoustic insulation and to increase radiation absorption are also covered.
Because of the many and varied materials and practices in Europe it is not possible for certain
aspects of the standard to enter into sufficient detail to be fully usable to practitioners in each country.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 998-1, Specification for mortar for masonry — Part 1: Rendering and plastering mortar
EN 13914-2, Design, preparation and application of external rendering and internal plastering - Part 2:
Design considerations and essential principles for internal plastering
3 Terms and definitions
For the purposes of this document, the terms and definitions in EN 13914-2 and the following apply.
3.1
plaster
mixture based on one or more binders, that is applied while plastic and that hardens after application,
used to obtain an internal surface finish. It does not acquire its final characteristics until it has set on
the building component
3.2
mineral plaster
mixture of aggregates, additives, admixtures and one or more binders
3.3
cement and/or lime plaster coat
obtained by application of one or more layers with one or more mixes of the same product
3.4
cement and/or lime plaster layer
cement and/or lime plaster applied wet on wet to obtain the final thickness with one or more mixes of
the same product, when all operations are completed before the cement and/or lime plaster has set
3.5
designed plaster
plaster designed and manufactured to fulfil stated properties and subjected test requirements
(performance concept)
3.6
prescribed plaster
plaster made in predetermined proportions the properties of which are assumed from the stated
proportions of the constituents (recipe concept)
3.7
plastering
application of plaster
3.8
plastering system
plaster coat or sequence of plaster coats applied to a background, including the possible use of a
support and/or reinforcement and/or pretreatment
3.9
undercoats
lower plaster coat or plaster coats of a plastering system
3.10
final coat
last plaster coat of a multicoat plastering system
3.11
dubbing out
process of filling large localized irregularities in the background, such as hollows, prior to the
application of an undercoat
3.12
one coat plaster
plaster applied in one coat which fulfils all the functions of a plastering system
3.13
background
surface of a construction element to which a plastering system is to be applied
3.14
reinforcement
material incorporated within a plaster coat to improve resistance to cracking (e.g. mesh)
3.15
support
product attached to the background to which a plaster is applied so that the plastering system is
largely independent of the background (e.g. lathing)
3.16
bonding agent
proprietary material used to provide adhesion of the plastering system to the background where
necessary
3.17
spatterdash and stipple
pretreatments to prepare a background for plastering. They do not form a coat in the plastering
system
NOTE Stipple is only used in the form of site plaster.
3.18
lining
true representation of a frame which was to be plastered up to e. g. doors, frames
3.19
depth gauge
mortar screed or metal bead used in setting for a required thickness
3.20
crazing
network of short, irregular and very fine cracks up to approximately 0,2 mm in width. Hairline cracks
do not impair the function of the plaster and are therefore acceptable to a limited extent
4 Materials and accessories
4.1 Materials for site-made plasters
4.1.1 Binders
4.1.1.1 Common cements including coloured cement
Common cements, which include coloured and pigmented cements, should conform to the
requirements of EN 197-1. It should, however, be noted that not all types and classes will be suitable
for each and every application.
4.1.1.2 Masonry cement
Masonry cement should conform to the requirements of EN 413-1.
4.1.1.3 Sulphate resistant cements
Sulphate resisting cements should conform to the requirements of relevant national standards or
provisions valid in the place of use of the plaster until a European Standard (EN 197) for sulphate
resisting cements is available.
4.1.1.4 Lime
Building lime should conform to the requirements of EN 459-1.
4.1.2 Aggregates
Aggregates should conform to the requirements of EN 13139 or EN 13055-1 as appropriate. Other
aggregates may be used which do not exert a harmful influence on the plaster.
4.1.3 Admixtures for cement and /or lime based plasters
Where available admixtures should conform to the requirements of EN 934-3.
Only those admixtures should be used which do not exert any harmful influence on the plaster. They
should not impair the strength or durability of the plaster and where applicable, the protection against
corrosion of the reinforcement or lathing. In addition they should not modify, other than in the manner
intended, the setting or hardening of the binder.
With all admixtures it is essential that the manufacturers instructions should be precisely followed.
Overdosage should be avoided.
4.1.4 Additions
4.1.4.1 Bonding agents
Only bonding agents with a proven performance should be used. With all bonding agents it is
essential that the manufacture's instructions should be precisely followed.
4.1.4.2 Pigments
Pigments should comply with the requirements of EN 12878. Other pigments should be used only if
they are known to be satisfactory.
4.1.4.3 Fibres
Fibres can be used in specialised applications such as restoration work, sprayed plasterings and
plasterings on lathing or insulation board.
The fibres should not affect the chemical or physical stability of the plaster.
4.2 Water
The water should be of a quality such that it does not adversely affect the plaster.
Water fit for drinking is suitable for mixes for plastering. Attention is drawn to the requirements of
EN 1008 in cases where water supplies may be of doubtful quality.
4.3 Types of plaster
4.3.1 General
Ready mixed plasters can be mixed entirely in the factory or partly in the factory and then completed
on site. Alternatively plaster may be mixed entirely on site.
4.3.2 Factory made and semi-finished factory made plasters
For mixes based on cement and/or lime, factory made and semi-finished factory made plasters should
conform to EN 998-1 for those parts of the process either wholly or partly carried out in the factory.
For those parts of the process for semi-finished factory made plasters completed on site, the materials
should conform to the recommendations of 4.1 and 4.2.
4.3.3 Site made plasters
4.3.3.1 General
Site made plasters should be made from constituents given in 4.1 and 4.2 and mixed in accordance
with 9.2 with the correct proportions (see 9.1).
4.3.3.2 Site made, designed mixes
It is recommended that such mixes should not normally be made on site unless the contractor has
taken special measures to exercise the necessary degree of control.
4.3.3.3 Site made, prescribed mixes
These mixes should be made by batching the specified binders and aggregates in appropriate
proportions. These proportions are not given in this document. Other than ensuring and checking that
these mixes are correctly batched prescribed mixes are not required to meet any test criteria.
NOTE It is recommended that other documentation should give a range of different mix proportions to
produce a range of plasters of different strengths. This will provide suitable products for backgrounds of different
strengths and suctions/absorptions and also for successive undercoats and final coats. The proportions given
should be the national traditional values for which there are many years of experience of successful use.
In some cases it might be appropriate to provide the mix proportions for a range of alternative binders
to produce mixes of equivalent strengths, for example:
 cement:lime:sand;
 cement:premixed lime/sand;
 cement:sand plus plasticizer;
 lime:sand.
Mixes can also be made and selected according to their use.
In stating the mix proportions it should be explained whether these are by weight or by volume and
whether they are based on the use of dry or damp sand and aggregates.
4.4 Reinforcement, lathing and beads
Lathing, reinforcement and beads of whatever type should be of stainless steel, galvanized steel,
aluminium or plastics, should conform to EN 13658-1. Reinforcement of alkali resistant glass fibre net
should conform to EN 13496.
Welded wire mesh reinforcement should conform to EN 13658-2.
4.5 Fixings
Fixings for lathing and beads such as nails, screws, staples and steel wire should be made of
compatible material and should conform to prEN 10223-3, EN 10230-1, EN 10244-1 or EN 10244-2.
4.6 Firings
Firrings should consist of galvanized or stainless steel channels, rods, steel wire or timber.
Firrings shall be of sufficient size so that the lathing and the plaster applied to the lathing is held rigidly.
5 Design – factors influencing the selection of cement and/or lime plastering
systems
5.1 Functions and properties that may be required
The function and properties achievable are determined by the choice of cement and/or lime type and
mixes.
A cement and/or lime plastering system will need to fulfil some of the following functions or properties:
 to even out any small unevenness in the background and provide a flat surface (see Table 5);
 to provide a decorative finish or a background for such a finish;
 to have enhanced strength;
 to have enhanced resistance to abrasion.
Special plasters can provide enhanced properties for the following aspects:
 to improve the thermal properties of a building element (see 6.4);
 to enhance the protection against water penetration;
 to enhance the protection against soluble salts and moisture (renovation plaster).
5.2 Factors influencing the choice of cement and/or lime plaster type or systems
The designer should consider all functional and aesthetic aspects of the building.
The choice of cement and/or lime plaster(s) or cement and/or lime plaster system is determined
principally by the plaster mix according to:
a) type of building (private houses, buildings); purpose of building (flat, school, hospital, office); uses
(for example: wet room);
b) the characteristics of the background;
c) the ambient and operating conditions;
d) the traditional usage in any particular area;
e) the type of finish required.
5.3 Background
Consideration should be given to the compatibility between cement and/or lime plastering systems
and the background. To achieve this compatibility, the following items should be considered:
a) The background should provide adequate support: strength, rigidity and adequate key and suction
for the adhesion of the cement and/or lime plaster.
b) Masonry should conform to the requirements of ENV 1996-2.
c) Boards, slabs and polystyrene should be fixed securely and should only be plastered when they
are dry and dimensionally stable.
d) It is important to avoid:
1) movement of the background, including structural, moisture and thermal movements;
2) defects in the background, e.g. lack of adequate key, weakness, contamination.
3) inadequate suction control;
4) efflorescence
Such compatibility is necessary to avoid bond failure between successive coats or between the first
cement and/or lime 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 should be used.
If it is necessary to plaster over an existing substrate, ensure that it will have sufficient bond strength
to support and provide adhesion for the new plaster. For most plaster types adhesion is provided by
key and suction from the background.
Care should be taken in the following circumstances:
 high and/or variable suction: when the suction is high a pre-treatment incorporating a primer
agent should be used;
 low key and suction: when the key and suction of a background is insufficient, then a pre-
treatment incorporating a bonding agent should be used.
When a cement or cement lime background is to receive a gypsum plaster coat, it is important that the
entire cement or cement/lime background is mature, clean and dry and a proper key provided,
otherwise difficulty with decoration due to the migration of alkalis may be experienced and in extreme
cases complete de-bonding of the gypsum plaster coat can occur.
6 Characteristics of cement and/or lime plastering systems
6.1 General
6.1.1 Cement and/or lime plasters
Cement and/or lime plasters have a controlled set. During the drying out process shrinkage may take
place depending on the materials of the plaster mix. Cement and/or lime plasters may be decorated
with most proprietary finishes when dry.
The appropriate cement and/or lime plaster can be used in most areas. Plasters for special designed
requirements are described in EN 998-1. Cement and/or lime undercoats should be scratched to
provide a key for subsequent coats. Each undercoat should be allowed to harden and dry before
applying the subsequent coat.
6.1.2 Lightweight cement and cement/lime plasters
Lightweight cement plasters have the general characteristics as described in 6.1 but are less brittle.
6.1.3 Mixes based on lime, or lime and cement, or lime and gypsum
Plasters containing a high percentage lime set relatively slowly by reaction of lime with carbon dioxide
from the air. Lime plasters are not hard or brittle.
Such lime plasters should not be used under persistently damp conditions.
Lime may be mixed with either cement or gypsum. Lime/cement and lime/gypsum plasters set faster
than lime plasters.
Products made with hydraulic lime harden in a similar manner to cement, i.e. without carbon dioxide
from the air. Hydraulic lime shall not be mixed with gypsum.
6.2 Damp conditions
Cement and cement/lime plasters can be used in damp conditions.
6.3 Impact and abrasion resistance
See 5.2.6 of EN 13914-2.
Plasters of classes CS III and CS IV in accordance with EN 998-1 are suitable for use where there is
a requirement for a higher level of impact and abrasion resistance.
6.4 Thermal insulation
See 5.3 of EN 13914-2.
Only a suitable final plaster coat should be used on thermal insulating cement/lime plaster undercoats.
The thermal insulating plaster may have one of two ranges of compressive strength as given in
Table 2 of EN 998-1. The strength of the final coat should be as given in Table 2 of EN 998-1. The
nominal thickness of the undercoat(s) should be in the range of 20 mm (minimum) to 100 mm and that
of the final coat(s) approximately 10 mm.
6.5 Acoustic properties
Cement and/or lime plasters do not contribute to sound absorption but they can contribute to the
continuity by avoiding phonic bridges. If special properties are required, then special acoustic plasters
should be used. Sound-absorbent finishes may affect sound transmission indirectly to some extent by
reducing the level of reverberant noise in either the source room or receiving room.
6.6 Resistance to cracking
When the background has been erected in accordance with the relevant standards and the cement
and/or lime plastering system prepared and applied in accordance with this document then the
cement and/or lime plastering system will perform satisfactorily.
6.7 Durability
The durability of cement and/or lime based plaster can be affected by the following:
 Lack of adhesion to the background and between coats.
 Alkali migration from the background.
 Contamination from the background e.g. oil, organic films, salts.
 Dust on the background.
 Movement in the structure
 Incorrect usage e.g. over a gypsum plaster.
 Persistent high humidity and dampness.
NOTE Crazing does not impair the performance of the plaster. They consist of micro-fissures which are
caused by differential shrinkage of the plaster surface.
6.8 Principles governing the number of plaster coats
The thickness that can be applied in one operation will depend upon the type of plaster chosen.
Dubbing out is not included as a coat in the system neither should its thickness be included in the
thickness of the plastering system.
The nature of the background and degree of accuracy of the finished surface required by the
specification will determine the number and thickness of plastering coats, as shown in a) and b) below.
The thickness, trueness and verticality of the plastering system is considered in 6.10 and EN 13914-2
a) Brickwork and blockwork if constructed to a close enough tolerance, may allow single or multicoat
work depending upon the tolerance of the background and the thickness of the coats applied. If
brickwork and blockwork is erected in accordance with the recommendations of ENV 1996-2,
they may not have sufficiently true and vertical surfaces to allow the use of a thin one-coat plaster
or a single undercoat.
b) In-situ concrete and some specially made units and constructed walls having a sufficiently true
and vertical surface and uniform suction may be suitable for single-coat work (see also 8.1.5).
c) The thickness of plaster applied to a solid soffit should be kept to a practical minimum to avoid
the risk of detachment (see also 8.1.6 and Table 2).
6.9 Thickness of plaster coats
6.9.1 General
Care should be taken when using thicknesses greater than those given in the tables and either
manufacturer's advice should be followed or a multicoat system used.
6.9.2 To solid backgrounds
The general range of total thicknesses for plasterwork to solid backgrounds is given in and
Tables 1 2
for one coat systems and Tables 2 to 4 for two coat systems.
The values given are exclusive of keys.
NOTE 1 The values of thicknesses given in Tables 1 to 4 are as recommended in many European countries.
Individual nations may replace the values given their own recommendations.
NOTE 2 Nations may recommend values for systems using other combinations of plaster types.
NOTE 3 In some areas, for instance due to unevenness of the background the thickness of plaster may be
reduced by up to 5 mm from the values given.
Table 1 — Recommended thicknesses for various types of one coat plasters to solid walls
Recommended range for application of plaster thickness (mm)
Binder Base of
Plaster types
plaster
General Purpose Lightweight (LW) Renovation (R) Thin
Skim coat (Spachtel)
1) 1) 1 1
Nominal Nominal Range Nominal Nominal
Minimum Minimum Minimum Minimum
Lime/gypsum 10 5 - - - - - - -
Lime 10 5 - - - 4 2 2 0,1
Lime/cement 10 5 10 5 - - - - -
Cement/lime 10 5 10 5 > 20, < 30 - - - -
Cement 10 5 10 5 > 20, < 30 - - - -
Polymer modified 6 2 6 2 - 3 1 - -
cement lime
1)
The minimum permissible thickness values should be limited to individual points only. For site made plasters these values may need to be
increased.
Table 2 — Recommended total thicknesses for various types of one coat and multicoat
plasters to soffits (the underside of floor slabs)
Values for soffits should be as for Tables 1 and 3 but with a maximum of 15 mm for keyed surfaces and 10 mm
for smooth surfaces. For fire regulatory purposes an increased thickness may be required, but special
precautions need to be taken with the selection of the materials and application.

Table 3 — Recommended total thicknesses for multicoat systems consisting of lime and
cement plasters onto solid walls and soffits (the underside of floor slabs)

Recommended range for application of
Binder base and plaster type in-
total plaster thickness (mm)
Undercoat Final Coat Walls Soffits
1) 1
Nominal Minimum Nominal Minimum
)
2)
Lime (GP) Lime (GP) 12 7 10 5
Lime/cement (GP) Lime/cement (GP) 12 7 10 5
Lime (GP) 12 7 10 5
Polymer 12 7 10 5
3)
Lime/cement(GP or LW ) Silicate 12 7 10 5
Silicon 12 7 10 5
Cement/lime (GP) Cement/lime (GP) 12 7 10 5
Lime (GP) 12 7 10 5
Polymer modified cement/lime 12 7 10 5
Polymer 12 7 10 5
Gypsum (GP) 12 7 10 5
Gypsum lime 12 7 10 5
Cement (GP) Cement (GP) 12 7 10 5
Gypsum (GP) 12 7 10 5
Gypsum lime 12 7 10 5
Polymer modified cement 12 7 10 5
Polymer 12 7 10 5
Note  — for renovation plasters (R) based on lime or lime/cement binders the
recommended range of total plaster thickness should be 20 to 40 mm, or
thickness otherwise recommended by the manufacturer.
— for cement based insulation plasters the minimum thickness for walls should
be 20 mm with the final coat being 6 mm to 10 mm.
— for site made plasters these values may need to be increased.
1)
The minimum permissible thickness values should be limited to individual points only.
2)
GP — General Purpose
3)
LW — Lightweight
Table 4 — Number of coats and thicknesses on to plasterboard walls and ceilings
Binder type Number of plaster coats in Total thickness of system
system to walls and ceilings (mm)
Lime with bonding agent primer 2 5 (walls) 3 max (ceilings)

Cement/lime 2 5 (walls) 3 max (ceilings)
Lime/cement 2 5 (walls) 3 max (ceilings)
1)
Polymer modified cement under coat 2 6 max
1)
This may include when a scrim and bed is used - non flush joint- square edge board plus scrim.

6.9.3 To metal lath
On metal laths the total thickness of finished plasterwork (measured from the front face of the laths)
should be not less than 10 mm for all types of plaster.
6.9.4 Service conduits and ducts
The thickness of cement and/or lime plaster will be a minimum cover of 5 mm the extreme protrusions
of any service duct or conduit.
For performances on fire, thermal insulation and acoustical properties, other thicknesses (minimum
and maximum) should be required depending of the national regulation and/or technical agreement.
6.10 Surface requirements
6.10.1 Flatness
The flatness of the plastered finish will depend upon the accuracy to which the background has been
constructed and the thickness of the plaster specified. Backgrounds which are built within the
tolerances specified in ENV 1996-2 may still not be able to be plastered plumb or to line unless
sufficient plaster thickness is specified. Thinner applications of plaster will only overcome minor
irregularities or small deviations from line of the background. In general, no tolerance can be specified
for very thin plaster coats since this will closely follow the contour of the background.
To achieve the required standard of surface finish where there are greater irregularities in the
background it will require:
 an additional levelling coat or coats;
 and/or a greater total plaster thickness.
Table 5 gives recommendations for classes of flatness of the plastered finish.
NOTE 1 Care should be taken that the thicknesses applied should not exceed the manufacturer's
recommendations.
NOTE 2 Under certain conditions where the plasterwork is subject to shallow angle lighting e.g. in long
corridors with end lighting, although within this deviation limit, plasterwork can still reveal minor inherent surface
irregularities.
Table 5 — Classes of flatness
Class Standard of finish Minimum standard of
required – gap under background flatness to
straight edge achieve standard of finish
required
0 No requirement No requirement
1 10 mm in 2 m 15 mm in 2 m
2 7 mm in 2 m 12 mm in 2 m
3 5 mm in 2 m 10 mm in 2 m
1)
4 3 mm in 2 m 5 mm in 2 m
1)
5 2 mm in 2 m 2 mm in 2 m
1)
This is only appropriate to a plastering system of 6mm plaster thickness or less.
NOTE National annexes may advise on plaster thickness required for given levels of
flatness and also the flatness class normally used.

6.10.2 Verticality of the background and the plastered finish
The background should be constructed to a suitable accuracy. The verticality of the plastered finish will
depend upon the accuracy to which the background has been constructed and the thickness of the
plaster specified.
Additionally the following should be provided:
 linings, openings and windows etc. to be in alignment
 grounds, depth gauge beads fixed to a correct plane.
6.10.3 Angularity
Recommended limits for angularity are given in Table 6, for use when a high degree of accuracy of
angularity between adjacent surfaces of the background and of the plaster finish are required.
Table 6 — Classes of deviation
Length of adjacent surface l
Deviation from right angle
m mm
l < 0,25
0,25 ≤ l <0,5 5
0,5 ≤ l < 1
1 ≤ l ≤ 3 8
Dimensions in mm
90 ˚
3 3
Key
1 Alternative angle of reveal
2 Reveal in plastered wall recess
l length of adjacent surface
NOTE See Table 6
Figure 1 — Example of measurement of angularity of plastered reveal showing length l, for l
less than 0,25 m
7 Types and standards of plaster finish
The final coat can be finished with a variety of finishes. These can range from smooth flat finishes to a
number of different types of textured, patterned or coloured finishes, e.g. scraped, felted and sprayed.
If the designer specifies a special plaster finish and trials to be made prior to the works (to ensure that
the plasterer can achieve the designer’s specification) this should be carefully described in the
contract documentation.
It is recommended that the levels of smooth finish used in relation to the decorative finishes described
follow Table 7.
l < 250
Table 7 — Standards of smooth finish
Level 1 for use in areas where finish is not critical
Level 2 to receive a textured wallpaper or a textured wall covering
or a textured paint
Level 3 to receive a matt paint or smooth wallpaper or smooth wall
covering
Level 4 to receive a semi-gloss paint and/or with glancing
1)
illumination
1)
Additional requirements may need to be specified for use with gloss paint.
Note: Level 1 is assumed to apply unless otherwise specified. Finished
plasterwork may need preparation for certain finishes.

8 Backgrounds, including preparation
8.1 Required characteristics of the background
8.1.1 General
The following background characteristics (see 8.1.2 to 8.1.9) should be considered when designing a
plaster system. Any precautions that may be necessary are described in 8.2, 8.3 and Annex A.
8.1.2 Strength
The background should have adequate strength with sufficient load bearing capacity and be
sufficiently resistant to deformation.
The strength of undercoat mixes should be related to that of the background.
8.1.3 Movements
Movements of backgrounds due to construction, moisture or temperature should be avoided. Such
movements lead to stresses such as shortening when changes occur in the background and/or
plastering system.
8.1.4 Surface dryness, cleanliness and previous coatings
The background should be sufficiently dry and free of dust and contamination.
Care should be taken when plastering over an existing coating to ensure that it will have sufficient
bond strength, to support and provide adhesion to the new plaster. For most plaster types adhesion is
provided by key and suction from the background.
8.1.5 Porosity and suction
Special precautions may need to be taken when backgrounds are likely to have non-uniform suction
properties. The porosity and suction of the background will influence whether there is a need for a
pretreatment, e.g. a bonding agent or primer to reduce suction. It is essential that the specification
therefore includes clear information on suction properties of the background and its pretreatment.
8.1.6 Bond
The background should be capable of providing adequate bond to support the full weight of the
plaster system and applied finishes.
8.1.7 Soluble salts and efflorescence
The background surface should be free of efflorescence.
8.1.8 Flatness and verticality of construction
The background surface should be built to a sufficiently true line to allow, the final plaster surface to
be applied to the tolerance required.
See 6.10 and 7 of this document and 5.9 of EN13914-2.
8.1.9 Unfrozen
The background surface should be free of frost, with a temperature above 5 °C.
8.2 Classes and types of backgrounds
8.2.1 General
In choosing the plaster type, the characteristics of the background should be considered (see 5.1.3
and 5.1.5 of EN 13914-2 and Table 8. For factory made plasters the type of cement or cement/lime
plaster should be chosen taking into account the background strength, key/texture and suction.
For site made and factory made plasters proportions should be chosen so that they are compatible
and less strong than the background. Care should be taken when backgrounds have high or variable
porosity/suction (see 8.1.5).
For repair and renovation work, see Clause 9 and Annex B. For backgrounds made of concrete,
calcium silicate or woodwool, consideration should be given to the possibility of drying shrinkage, and
hence their age and moisture content as appropriate. For backgrounds made of polystyrene the
effects of shrinkage and age should be considered.
Boards and slabs should be fixed securely and only when they are dry and dimensionally stable
should they be plastered.
Table 8 — Recommended plastering systems for various backgrounds (Refer to Key for
explanation of letter codes)
Plaster coat¾¾¾¾ Cement and cement/lime
BackgroundÀÀ Lime or lime/ Cement or cement/ One coat cement Thermal Renovation
ÀÀ
cement undercoat lime undercoat or cement lime insulating
1. Rough dense concrete B1/B2 B1/B2 B1/B2 B1/B2 B2
2. Smooth dense concrete C C C C -
3. Lightweight clay brickwork A,H, D A, H, D A, H, D A -
4. Clay brickwork A A A A J
5. Dense clay brickwork C C C C J
6. Calcium silicate brickwork B1/B2 B1/B2 B1/B2 B1/B2 -
7. Calcium silicate blockwork B1/B2 B1/B2 B1/B2 B1/B2 -
8. Dense concrete masonry B1/B2 B1/B2 B1/B2 B1/B2 J
9. Lightweight concrete masonry A, D, H A, D, H A, D A J
10. Autoclaved aerated concrete B3, D, H B3, D, H B3, D A -
masonry
11. Natural stone and rubble B1/B2 B1/B2 B1/B2 B1/B2 J
masonry
12. Wood wool slabs E1, D E1, D E1, D E1 -
13. Wood wool formwork blocks E1, D, K E1, D, K E1, D, K E1, K -
14. Polystyrene formwork blocks C, D, E1, K C, D, E1, K C, D, E1, K - -
15. Expanded polystyrene board C, D, E1 - C, D, E1 - -
16. Extruded polystyrene board C, D, E1 - C, D, E1 - -
17. Cork board C, D, E1 - - - -
18. Gypsum plasterboard - - C, E1, G - -
19. Existing plasterwork F F F F F
20. Fibre cement board - - - - -
21. Metal lathing D, H D, H D - -
22. Wood lathing F F F F F
23. Gypsum blockwork - - - - -
24. Mixed masonry B2, E2 B2, E2 B2, E2 B2, E2 J, E2

Key to letter codes in Table 8
A Normally satisfactory except where product F See Clause 10.
specific (i.e. background material) treatment is
required.
B1 Pre-treatment is required depending on G Joints may need to be reinforced, depending
condition of background using cement or on board type.
cement/lime and aggregate and polymer.
Sufficient drying time important when gypsum
plaster is used.
B2 Pre-treatment is required depending on H Care should be taken in the choice of mix to
condition of background using cement or give correct strength relative to background
cement/lime and aggregate. (site made plasters).
B3 Pre-treatment is required depending on J If pre-treatment is required depending on
condition of background using a suction condition of background then pre-treatment
reducing agent. should not completely cover the background.
C As B2, but is required on all backgrounds using K Consider the time period from concrete
cement or cement/lime and aggregate and placing in formblocks to plastering.
polymer.
D Care should be taken in the choice of cement — Not recommended or applicable only after
plaster type and cement/lime plaster type careful clarification.
(factory made plasters).
E1 Reinforcement is required (see Annex A).
E2 Reinforcement may be required (see Annex A).

8.2.2 Concrete backgrounds
Dense concrete, because of its lack of absorbency, will not afford a satisfactory bond for plasters
unless it is textured. Special measures shall be taken to ensure an adequate bond, e.g. use of a
bonding agent.
8.3 Bonding pretreatments for use with cement, cement and lime, and lime based
plaster
8.3.1 General
When using factory made plasters it may not be necessary to use a pre-treatment on rough, high
suction backgrounds. For site made and semi finished plasters it may be necessary to use a
1)
spatterdash or stipple pretreatment when plastering onto smooth, dense surfaces in order to provide
an effective textured key.
8.3.2 Spatterdash and stipple
8.3.2.1 Site-made mix for spatterdash (see system B2 of Table 8)
This should consist of cement and clean coarse sand, possibly with a small amount of lime. A bonding
agent may be incorporated in the mix.

1)
In some countries the provision of a specific type of preparatory treatment may be obligatory.
8.3.2.2 Site-made mix for stipple (see systems B1 and C of Table 8)
This should be the same as that for spatterdash but a bonding agent should always be used. Curing and
checking should be the same as for spatterdash.
8.3.2.3 Factory-made spatterdash (see system B2 of Table 8)
This should be applied in accordance with the manufacturer’s instructions.
8.3.2.4 Special factory made plasters incorporating bonding agents (see systems B1 and B2
of Table 8)
Adhesion to smooth backgrounds e.g. Concrete, brickwork and extruded polystyrene can be
enhanced by spray applying special factory made plasters incorporating bonding agents (using a
trowel with a serrated edge) for between one to three days before applying the undercoat.
8.4 Preparation of background
8.4.1 General
Backgrounds to be plastered shall be examined for contamination, key, suction and strength (e.g. all
dust, loose material, any contamination such as splashes of oil or plaster may be all that is needed
and any organic growth or efflorescence on the wall should be removed). The recommendations for
various types of new background are given in Table 8.
Walls that have previously been painted should be carefully examined, and any necessary measures
taken before plastering.
Where a movement joint occurs in the background, an equivalent movement joint should be provided
in the plastering at the same location.
The background may be judged by visual examination, wetting, scratching, and/or by the wiping test.
8.4.2 Preparatory pretreatment
Smooth, dense surfaces can be provided with a suitable key or splatterdash by applying a preparatory
pre-treatment. The type of preparatory pretreatment will vary with the type of plaster to be used, and
the type background to be plastered (see 8.3 and 8.4). The recommended pretreatments are given in
Table 8.
Backgrounds should have uniform suction properties. Therefore it may be necessary to apply a primer
to reduce suction, e.g. system B3 as specified in Table 8.
Bonding agent with mineral bonding mortar and the addition of a polymer dispersion may be used for
a lime and cement lime plaster.
8.4.3 Treatment of mixed backgrounds
Suitable measures shall be taken where plastering is to be continued across backgrounds of different
materials, e.g. concrete abutting masonry. The type of measure, e.g. joints or support will depend on
the individual situation.
9 Preparation and application of cement and/or lime plasters
9.1 Proportioning of mix materials on site
9.1.1 General
Mix proportions, if applicable, are given in national standards.
9.1.2 Prescribed mixes
Prescribed mixes are usually proportioned by volume.
9.1.3 Designed mixes
Designed mixes should be proportioned by volume or by weight depending upon which method was
used in the design.
9.1.4 Vol
...