Repair Methods for Rendered Structures Rak Repair Methods of Structures, exercise (4 cr) Esko Sistonen

Anon. 2005: Rendering Book Helsinki. BY p. (in Finnish) This kind of cracks in facade are usually a sign for uneven settling of the building foundations.

Repair methods To do nothing Coating and patch repair methods – Light coating repair (minor patch repairs, coatings) – Full patch and coating repair Covering repair methods – repair of entire facade, for instance, with an – insulating rendering Demolition and reconstruction – Rendering removal and re-rendering Related repairs – Decreasing the level of exposure – Repairs based on damaged underlayer

Different factors which has influence on decision of repair method Lahdensivu, J Selection of repair methods for rendered facades. In: Carpinteri et al. (eds.). Fracture Mechanics of Concrete and Concrete Structures. Vol. 3. High-Performance Concrete, Brick-Masonry and Environmental Aspects. Proceedings of the 6th International Conference on Fracture Mechanics of Concrete and Concrete Structures, Catania, Italy, June 2007 pp

Selection of suitable repair alternative for each case has several demands: The repair must be cost effective Aesthetic requirements Degree of different deterioration mechanisms Service life requirements of repair Requirements concerning the reliability of the repair

Repair methods of rendering damage Anon. 1999: Rendering Book. Helsinki. BY p. (in Finnish)

Treatment methods for rendering surface

Different removal methods for old rendering

Rendering repair products Lime mortar Lime cement mortar Cement mortar Mortar is chosen depending on the case: -In patch repairs as same as the old -In re-rendering based on underlayer characteristics: rendering mortar layers should be weaken towards the surface, trowelled rendering should not be stronger than underlayer. Mortar additives: -air-entraining agent -retarders -polymers -fibers -seal and hydrophobic substances -pigments L (K) Lime HL (K h ) Hydrolic lime C (S) Cement LC (KS) Lime and cement e.g. LC (KS) 35/65/600

External wall insulation

Rendered Facades: Thick Rendering Thick rendered facade with slab insulationTimber frame - thick rendering -solution

Rendered Facades: Thin Rendering Rendered facade with slab insulationRendered facade with lamella insulation

Rendered Facades: Thin Rendering julkisivuratkaisut/serpotherm-eristerappaus-hienoroiskepinnalla.html

Tree coat rendering Mineral wool with lime- or limecement mortars The tree coat rendering has been fasten with mechanical anchor to buildings framework. Hot-dip galvanised welded wire mesh (  1 mm #19 mm) Base plate etc. Thin rendering Mineral wool or expanded polystyrene (EPS) cement-based and usually polymer modificated mortars Rendering is fixed to insulation with mortar and mechanical plastic fasteners. In some cases there are no mechanical anchors. Plastic-coated glass fibre alkali-resistant reinforced mesh Base plate etc.

Several internet links and publications… me=file me=file LimeRen pdf?sequence=1 Perander Thorborg; Råman Tuula (1985) Ancient and modern mortars in the restoration of historical buildings. VTT, Espoo. 74 p. + app. 24 p. Tiedotteita 450 / Valtion teknillinen tutkimuskeskus. Konow, von Thorborg (1989). Saltvittring i tegel – saltvittringsmekanismer. VTT, Espoo. 68 p. + app. 8 p. Tiedotteita 1003/ Valtion teknillinen tutkimuskeskus.

Several standards…  SFS-EN (September 2010). Specification for mortar for masonry - Part 1: Rendering and plastering mortar.  SFS-EN (February 2000). Methods of test for mortar for masonry - Part 12: Determination of adhesive strength of hardened rendering and plastering mortars on substrates.  SFS-EN (September 1998). SFS-EN /A1 (October 2004). Methods of tests for mortar for masonry – Part 19: Determination of water vapour permeability of hardened rendering and plastering mortars.  SFS-EN (December 2002). Methods of test for mortar for masonry - Part 21: Determination of the compatibility of one-coat rendering mortars with substrates.  SFS-EN (May 2005). Metal lath and beads - Definitions, requirements and test methods - Part 2: External rendering.

Several standards…  SFS-EN (March 2005). Design, preparation and application of external rendering and internal plastering - External rendering.  SFS-EN (May 2005). Design, preparation and application of external rendering and internal plastering - Part 2: Design considerations and essential principles for internal plastering.  SFS-EN (July 2009). Specifications for external renders and internal plasters based on organic binders.