This method statement outlines the procedures for plastering works, including the necessary steps, materials, and safety precautions to be followed during the plastering process. It is essential to ensure that the plastering work is carried out efficiently, effectively, and safely, adhering to industry standards and best practices.
This method of statement for plastering includes the following:
- Internal Portland cement plaster.
- External Portland Cement plaster.
- Formed in Place plaster grooves in elevation.
- External Formed in-place decorative cornices in building elevation.
Materials for Application.
- Portland Cement ASTM C150 Type.
- Sand Aggregate ASTM C 897 White Sand for the base coat, and red sand for the dash coat.
- Plastering Accessories: Metal Lath, angle beads, special pieces for internal angles and corners.
- Trial Mix.
- Details for Metal Lath Location and Installation
- Clean the surface and remove any dust, contaminated materials on plaster bases and substrates for direct application of plaster, removing loose material and substances that may impair the work.
- Form ties and other obstructions shall be removed or trimmed back even with the surface of the solid base.
- Dissimilar Backgrounds: where rendering is to be continued without breaking across joints between dissimilar solid backgrounds which are in the same plane.
- Cover joints with 200mm wide galvanized steel lathing as specified & approved fixed with corrosion-resistant fasteners at not more than 600mm centers along with both edges and apply mesh over electro-mechanical embedded conduits.
- Apply forcefully dash coat on concrete and concrete masonry surfaces indicated for direct plaster application. Dash coat is to cover the full surface to be plastered and is to provide a rough surface of sharp protrusions ranging from 3.0mm and 5.0mm.
- Dash-Coat Mix: 2 volume parts portland cement to 3 volume parts fine sand, 1 part bonding agent to 3 parts clean water mixed to a mushy-paste consistency shall be left undisturbed, and moist cured for at least 24 hours after application and before plastering.
- Install temporary grounds and screeds to ensure accurate rodding of plaster to true surfaces. Check the straightness in each corner and add grout to hold the external corner beads in a correct and internal position to be fixed using corrosion-resistant fasteners.
- Before plastering starts, dampen, by spraying water on concrete dash coat surfaces that are to receive plaster with clean water.
- All plaster shall be prepared in a mechanical mixer mix 1:5 (1 part cement and 5 part sand) using sufficient water to produce a workable consistency.
- Mix fiber 0.6 kg/m3 of the mortar or plaster by first mixing it with some water (30%). After all the ingredients have been added including the remaining mixing water,
- The plaster should be mixed for a further few minutes until uniform fiber dispersion. Plaster not used within 1.5h from the start of mixing shall be discarded.
- The second coat shall be applied with sufficient material and pressure to ensure tight contact with the dash coat.
- The surface of the second coat shall be brought to a true, even plane with a rod or straightedge, filling surface defects in place with plaster.
- Applied plaster shall be floated as smoothly as possible and then steel-troweled. Steel troweling shall be delayed as long as possible and used only to eliminate the uneven points and to force aggregate particles into the plaster surface.
- Each plaster coat shall be applied to an entire wall or ceiling panel without interruption to avoid cold joints and abrupt changes in the uniform appearance of succeeding coats.
- Wet plaster shall abut set plaster at naturally occurring interruptions in the plane of the plaster, such as corner angles, openings, and control joints where this is possible.
- Make internal angles and corners square.
- Finished grooves shall be neat, of uniform width and depth, with sharp straight edges, and exact vertical and horizontal lines. Elevation grooves shall be cut before plaster sets by using a molded guide or wooden strip and fixing it in temporary grout and screed. Regarding recessed, follow the procedures the same as grooves.
- Form cornices by plastering additional coats against pre-formed wood templates fixed onto plastered elevation.
- Make form wood templates to shapes, dimensions, and projections indicated on drawings. Apply additional undercoats in thickness not more than 10mm until obtaining the required projection.
- Plaster should not deviate more than plus or minus 3mm in 3m from a true plane in finished plaster surfaces, as measured by a 3-m straight edge placed in any location on the surface.
- Provide sufficient moisture in the plaster by spraying water as frequently as required at least twice per day.
4. Cutting and Batching
- Cut, patch, replace, repair, and point up plaster as necessary to accommodate other work. Repair cracks and indented surfaces. Repair work to eliminate blisters, and buckles, check to crack, and dry out as necessary to comply with visual effects.
- To correct inaccuracies, dubbed out in thickness of not more than 10mm in the same mix as a base coat and the total thickness of
- Dubbing must not exceed 25mm unless otherwise approved.
- In areas where the thickness is more than 20mm, apply a dash.
- keying mix before adding a new layer.
- To correct inaccuracies in beams, and columns together with block work, chip carefully the concrete structures by using a hammer and chisel to receive a dash coat.
- For 25mm thick plaster repair apply it one time as per 2. B. For 45mm thick, apply 20mm first coat and apply keying mix before adding the new layer. Each layer must not exceed 10 mm.
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