EN 13914-1:2005

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Projektiranje, priprava in uporaba zunanjih in notranjih ometov - 1. del: Zunanji ometiPlanung, Zubereitung und Ausführung von Innen- und Außenputzen - Teil 1: AußenputzConception, préparation et mise en oeuvre des enduits extérieurs et intérieurs - Partie 1: Enduits extérieursDesign, preparation and application of external rendering and internal plastering - External rendering91.100.10Cement. Mavec. Apno. MaltaCement. Gypsum. Lime. MortarICS:Ta slovenski standard je istoveten z:EN 13914-1:2005SIST EN 13914-1:2005en01-junij-2005SIST EN 13914-1:2005SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 13914-1March 2005ICS 91.100.10English versionDesign, preparation and application of external rendering andinternal plastering - External renderingConception, préparation et mise en oeuvre des enduitsextérieurs et intérieurs - Partie 1: Enduits extérieursPlanung, Zubereitung und Ausführung von Innen- undAußenputzen - Teil 1: AußenputzThis European Standard was approved by CEN on 15 December 2004.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.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 STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2005 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 13914-1:2005: ESIST EN 13914-1:2005

General guidance on the selection of site mixed prescribed renders mixed according to background type).57 Annex B (informative)
Restoration of renders on old and historic buildings).58 Bibliography.63
The term ‘rendering mortar’ is used in the European Standard product specification EN 998-1, but to reflect common usage in relation to this document and for ease of reference the term ‘render’ (noun) has been used. A rendered finish may be applied to a variety of backgrounds, either to improve resistance to rain penetration and weathering and/or for aesthetic reasons. For the purposes of this document (except where stated in relation to a specific product standard) the term ‘strength’ should be considered in terms of relative strengths between different types of backgrounds compared with the nominal strengths of prescribed render mixes. Although it may be possible to consider this in terms of compressive strength, this standard deals with aspects of a craft as opposed to design calculations. Therefore ‘strength’ is not considered in terms of numerical values derived from test. Similar considerations also apply to terms such as ‘movement’, ‘absorbency’ and ‘permeability’ etc. used in this document. This document refers only to the technical suitability of materials and/or procedures. The user will during the application need to observe any legal obligations relating to health and safety at any stage. The values of certain parameters in this document may be set by CEN members so as to meet the requirements of national regulations.
These parameters are designed by |_| in the text. Because this document is a code-like document as opposed to the more conventional EN product standard, it is appropriate to mention that, as with product standards, the use of the verbal form 'shall' denotes a requirement for which verification of compliance has to be able to be demonstrated. Recommendations are denoted by the verbal form 'should' and should be followed unless there is a justifiable reason for not doing so. It is not the function of this standard 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. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: 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 and United Kingdom.
1) This document contains certain elements of specification and other requirements which are denoted by the use of the verbal form 'shall'. SIST EN 13914-1:2005

The use of such products externally will depend upon the climatic conditions where the render will be used and on the local building traditions.
With the exception of some drier countries in southern Europe gypsum based renders are generally not recommended for external use and are therefore not included within the scope of this document.
Their use may be permitted and controlled locally2. f) the design and installation of flashings at windowsills and elsewhere. At various points in this document reference is made to the use of sealants. The specification of sealants and the design of such joints is outside the scope of this document. 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 197-1, Cement — Part 1: Composition, specifications and conformity criteria for common cements EN 413-1, Masonry cement — Part 1: Composition, specifications and conformity criteria. EN 459-1, Building lime — Part 1: Definitions, specifications and conformity criteria
2) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

3) NOTE (to English version only)
The term ‘rendering mortar’ is used in the European Standard product specification
EN 998-1, but to reflect common usage in relation to this document and for ease of reference the term ‘render’ (noun) has been used. SIST EN 13914-1:2005

properties of which are assumed from the stated proportions of the constituents (recipe concept) 3.13 render system coat or sequence of coats to be applied to a background which can be used in conjunction with a support and/or reinforcement and/or a preparatory treatment 3.14 final coat ultimate coat of a multicoat rendering system 3.15 renovation render designed render for use on moist backgrounds containing water soluble salts 3.16 reinforcement material incorporated into a render system to improve resistance to cracking SIST EN 13914-1:2005

5.1.2 Aggregates Aggregates with established suitability for use in renders shall be used. Aggregates shall conform to the relevant standard, when suitable. Lightweight aggregates shall conform to EN 13055 and aggregates for mortar shall conform to EN 13139. 5.1.3 Admixtures Where available, admixtures shall conform to EN 934-3. Only those admixtures shall be used which do not exert any harmful influence on the render.
They shall not impair the strength or durability of the render, or, where applicable, the protection against
4) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

Manufacturers' literature should be consulted for likely improvements to the render as well as limitations on use and long term deterioration. Metal fibres shall have adequate durability.
Metal fibres shall not be adversely affected by alkaline or weak acid conditions. 5.1.4.2 Pigments Pigments shall conform to EN 12878 and be used only if they are proven to be satisfactory.
Pigments shall be stable, unaffected by lime or exposure to light. They shall not easily be leached out by water nor shall they have any adverse effect upon the cement or other constituents of the rendering. 5.2 Water The water shall be of a quality such that it does not adversely affect the render. Water fit for drinking is suitable for mixes for rendering. Attention shall be drawn to the requirements of EN 1008 in cases where water supplies may be of doubtful quality. 5.3 Types of render 5.3.1 General Ready mixed renders can be mixed entirely in the factory or partly in the factory and subsequently completed on site. Alternatively, render may be mixed entirely on site. Further detailed design recommendations and sub-division according to location of manufacture and purpose are given in 6.17. SIST EN 13914-1:2005

Plain welded wire mesh of stainless steel or of zinc coated steel prEN 13658-2 For supports, mesh should be of 10 mm to 40 mm pitch with wires not less than 1 mm diameter.
Where the aggregate grain size exceeds 3 mm consideration should be given to using a mesh larger than 15 mm. Welded mesh of this kind is used primarily as a support when rendering over certain backgrounds.
For reinforcement the mesh size should be no greater than
25 mm × 25 mm. Reinforcement Non-metallic mesh made from alkali resistant mineral fibres - With the strands from the two directions connected together. Support Slab-type supports, e.g. lightweight woodwool slabs
(Use of materials with established suitability) Stainless steel, polyvinyl chloride or combinations thereof prEN 13658-2 Should be used under local situations or regional conditions of high humidity and/or salt laden atmospheres or salts in background (see 6.12) Angle beads, corner beads, stop beads and render stops and profiles for special purposes Zinc coated steel) prEN 13658-2 Careful consideration should be given to the choice of this type of material for its use in local situations or regional conditions of high humidity and/or salt-laden atmospheres or salts in background (see 6.12) Metal lathing, reinforcement and beads of whatever type shall be suitable for external use. Steel other than stainless steel shall be zinc coated after manufacture of the finished product. After fabrication the items shall be hot dip zinc coated. SIST EN 13914-1:2005

Product Material Specification Nails Stainless steel or
zinc coated steel _ Pins for shot-firing Stainless steel or
zinc coated steel _ Staples Stainless steel or
zinc coated steel - Screws and bolts a Stainless steel or zinc coated steel _ Soft fixings and ancillary components Polyamide, polypropylene or polyethylene _ Washers, ancillary angles and brackets b Zinc coated steel or otherwise suitably coated or thermoplastics _ Wire Stainless steel or zinc coated steel prEN 13658-2 NOTE
The fixings for lathing and beads should be made of a material compatible with adjacent materials.
a Including expanding bolts and drill anchors.
b Often used in conjunction with shot-fired or screwed fixings.
5.5.2 Fixing blocks in solid backgrounds Only dovetailed shaped blocks that can be cast in should be used. Some types of plastics, e.g. high density polyethylene and some cement composite blocks have proved satisfactory. Wooden blocks shall not be used.
5) Materials for fixings5) SIST EN 13914-1:2005

Wooden plugs shall not be used. It is recommended that those responsible for the rendering should satisfy themselves on the adequacy of any method of fixing before commencing work (see 4.1 and 4.2). NOTE Some countries may limit the types of material permitted for use as plugs6). 5.6 Firring Firrings may consist of galvanised or stainless steel or timber. Galvanising shall be in accordance with the EN ISO 1461. Timber shall be given an appropriate preservative treatment (see also 7.4.3.1). 6 Design considerations 6.1 General factors affecting the design of the rendering system 6.1.1 Choice of render type, mix, number of coats and thickness The choice will depend upon the appearance desired, exposure conditions (see 6.5), nature of the background (see 6.3) and the functional requirements. These factors should therefore receive consideration together. The render type and mix shall be chosen to be compatible with the characteristics of the background, particularly its strength7) and whether it will move (see 6.2). Inter-coat compatibility should also be considered. A rendering system normally comprises at least two layers, namely an undercoat and a final coat, except for specially formulated products, e.g. one-coat renders that conform to the requirements of EN 998-1 (see 6.18, Table 5 and Table 6) Recommended thicknesses are given in 6.18 and Table 58). 6.1.2 Preparation of the background The method adopted will be dictated by the type and characteristics of the background (see 6.2).
Consideration should be given as to whether the background provides:  adequate strength and rigidity for support of the render and  adequate and uniform key and suction for adhesion of the rendering. If these characteristics of the background are inadequate, then other means of providing support and/or key will be required (see 7.4).
6) Refer to Note 1 of Clause 1 for further information. 7) Refer to NOTE 1 of Clause 1 for further information. 8) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

Masonry backgrounds, including the mortar joints, should be no weaker and preferably slightly stronger than the rendering.
On weaker backgrounds, rendering mixes should be restricted to weaker mixes9). 6.2.3 Suction of the background Adhesion of a rendering is determined to a great extent by the suction of the background, especially where there is no adequate key. Both high suction (which removes mixing water quickly) and low suction tend to impair the development of a good bond. It should be appreciated that the suction of a background can be significantly affected by its moisture content at any given time. 6.2.4 Key of the background Keys may be provided naturally or artificially and should be regularly spaced over the whole surface. Backgrounds should be clean, dust-free and free of all deposits that might impair the key of the render. For backgrounds which do not provide a natural key, methods of supplying a key are given in 7.4. 6.2.5 Joints in the background The design shall specify the type and execution of joints. Joints in the render shall be coincident with movement joints in the structure and allow for the same degree of movement. Other backgrounds, e.g. walls with insufficient movement joints, or junctions between dissimilar materials have the potential to crack after they have been rendered. 6.2.6 Cracks in the background Special measures shall be taken when rendering backgrounds with existing cracks, such as using reinforcement or supports (see Table 2). Cracked backgrounds cannot be rendered without risk. Backgrounds should be stable, (but see also 6.13 and 7.4.3). 6.2.7 Dimensional stability of the background Dimensional changes of the background should have largely taken place prior to rendering. Render applied to backgrounds which may move are likely to crack, e.g. with movement of the structure, deflection of floor slabs, shrinkage of concrete, high moisture content of masonry (but see 6.2.5 and 6.13.2).
9) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

(see 7.4.2.1 and 7.4.2.2).
On absorbent backgrounds the spatterdash or stipple or mineral bonding agent should be used to reduce or to even out varying suction.
These preparatory treatments give a rough-textured surface. SIST EN 13914-1:2005

Background Precaution a a) Clay, concrete and calcium silicate brickwork Depending on suction and key; may need use of a spatterdash or stipple preparatory treatment or key with polymer modified cement mortar or metal lathing b) Lightweight clay blockwork The suction should be checked to ensure that it is similar to that with normal clay bricks.
If not, special precautions may be necessary c) Lightweight blockwork: lightweight aggregate concrete Ordinary suction- no pre-treatment necessary High suction- use a spatterdash or stipple treatment or metal lathing d) Large lightweight concrete elements Special precautions in accordance with the recommendations of the manufacturer of the element or render e) Lightweight blockwork: autoclaved aerated concrete May need to use a suction reducing treatment f) Normal weight and dense aggregate concrete blockwork Depending on suction and key; may need use of a spatterdash/stipple treatment key with polymer modified cement render or support g) Sandstone blockwork Use a spatterdash and a water-resistant or renovation render h) Dense concrete If the surface is not rough then use a preparatory treatment, e.g. key with polymer modified cement render i) No-fines concrete No pre-treatment necessary j) Formwork blocks – cement/aggregate based Use a special preparatory treatment as recommended by the block manufacturer k) Cement/wood based blockwork a) lime/cement render: use spatterdash or stipple coat b) lime/cement lightweight render; none, but use glass fibre mesh c) lime/cement thermal insulating render: use spatterdash or stipple coat and glass fibre mesh. A metal support is recommended l) Woodwool boards (with or without thermal insulation) b c a) lime/cement render: use spatterdash or stipple coat and glass fibre mesh b1) on small areas lime/cement lightweight render: no pre-treatment necessary, but use glass fibre mesh in the undercoat (if single coat). For two coat work see b2) b2) on large areas Lime/cement light weight render: no pre-treatment necessary. The first undercoat is unreinforced and after sufficient drying time10) apply second thin undercoat reinforced with glass fibre mesh. c) lime/cement thermal insulating render: use spatterdash/stipple coat and glass fibre mesh or metal support
10) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

Background Precaution a m) Extruded and expanded polystyrene and polyurethane boards c Use a special preparatory treatment. For rendering see woodwool (items b and c) a The manufacturer of the background material/product may recommend special preparatory treatments. b Wood wool should be dry and protected from wet weather. c Board joints should be tight. Methods of preparing board surfaces are: i) Overlaying with reinforcement as described in 7.4.3.3 and 7.4.3.4; ii) For boards made of polystyrene and polyurethane that have rough surfaces, proprietary pre-treatment systems are available using thin layers of polymer modified cement based renders.
Such products should be left for at least one day before application of the rendering system.
6.4 Durability of the rendering External rendering that has been correctly designed will perform satisfactorily.
However in the design, consideration should be given to the factors that influence the durability of a rendering.
These are:  design and choice of suitable render or render system for the intended purpose;
 e.g. damage from abrasion and impact (see 6.11);  corrosion of embedded metal (see 6.12);  appropriate design of joints;  compatibility of render with the background and adequate adhesion;  deformation of adjacent components or building elements;  cracking and crazing (see 6.13);  rain penetration and rising damp (see 6.6);  problems associated with soluble salts (see 6.8);  effects of atmospheric pollution and frost action (see 6.9 and 6.10). Durability of the rendering will also be dependent upon the type of background, the type of rendering, mix proportions and the method of application. 6.5 Conditions of exposure This document does not contain specific recommendations for particular products, mix proportions and admixtures for various exposure situations11). The design should always take into consideration local knowledge and experience for the decision on which category of capillary water absorption given in EN 998-1 and which render to specify.
11) Refer to NOTE 1 of Clause 1 for further information. SIST EN 13914-1:2005

Such protective features become more important in more severe conditions). 6.6 Resistance to rain penetration The structure should be designed and constructed so that the background remains as dry as practicable during construction. The purpose of the completed render is to restrict rain penetration into the background. Therefore rendering should be as free from cracking as practicable (see 6.13). The design of the structure should take into account any special precautions needed when the outer leaf of a fully filled insulated cavity wall is to be rendered. For backgrounds which are dependent upon the rendering for protection, the following general principles should be adopted: a) for site made renders, especially when using prescribed mixes, the mix proportions and numbers of coats for any given condition of exposure to rain should be chosen based upon a knowledge of local successful use12).
The use of two undercoats will give better rain resistance. b)
for factory made renders: 1) in severe conditions of exposure, where the rendering is subject to much rain, renders which conform to the requirements of EN 998-1 and having a capillary water absorption Class W2 should be used. 2) in moderate and sheltered conditions, renders which conform to the requirements of EN 998-1 with a capillary water absorption Class W1 or W0 should be sufficient. 6.7 Resistance to water rising from the ground without pressure Special waterproofing measures are required where the masonry is in contact with the ground. Special renovation renders conforming to the requirements of EN 998-1 can be effective when used on masonry backgrounds susceptible to dampness and could be used in conjunction with other measures to minimize dampness (see also Annex B). 6.8 Soluble salts Soluble salts, particularly sulfates, may occur in backgrounds consisting of some types of clay brick or block, some types of aerated concrete blocks and in old backgrounds where they may also occur from a variety of extraneous sources e.g. rising damp. Salts have certain harmful effects that may lead to, disintegration of the background, cracking and loss of adhesion with the rendering and corrosion of any non corrosion-resistant metals. Backgrounds containing soluble salts which are likely to remain wet for prolonged periods, may adversely affect the render, so consideration should be given to either limiting salt content in new construction or reducing its effects.
12) Refer to NOTE 1 of Clause 1 for further information.
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