METHOD OF STATEMENT FOR PLASTERING

METHOD OF STATEMENT FOR PLASTERING

Summary: This Method of Statement 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 1 (Trans. # C-0238)(Submission for Approval).
• Sand Aggregate ASTM C 897 White Sand for base coat, red sand for dash coat. (Submission for approval)         (Trans.# C-0238)
• Plastering Accessories: Metal Lath, angle beads, special pieces for internal angles and corner. (Transmittal No#   C-1A,1B & 1C-A-0204).
• Fiber  (CMCI) (Transmittal # C-1A,1B & 1C-A-0203)
• Trial Mix (Trans.#C-0261) (Submission for Approval)
• Details for Metal Lath Location and Installation (Typical) (Submission for Approval) (Trans.# C-0260).

1. Preparation  

1. 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 obstruction shall be removed or trimmed back even with the surface of the solid base.
2. Dissimilar Backgrounds: where rendering is to be continued without break 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 both edges, apply mesh over electro-mechanical embedded conduits.
3. Apply forcefully dash coat on concrete and concrete masonry surfaces indicated for direct plaster application. Dash coat is to cover full surface to be plastered and is to provide rough surface of sharp protrusions ranging 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 part clean water mixed to a mushy-paste consistency shall be left untroweled, undisturbed and moist cured for at least 24 hours after application and before plastering.
4. 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 correct and internal position to be fixed using corrosion resistant fasteners.
5. Before plastering starts, dampen, by spraying water concrete dash coat surfaces that are to receive plaster with clean water.

2. Application   

1. 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 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 fibre dispersion. Plaster not used within 1.5h from start of mixing shall be discarded.
2. The second coat shall be applied with sufficient material and pressure to ensure tight contact with dash coat.
3. 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.
4. Applied plaster shall be floated as smooth 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.
5. 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.
6. Make internal angles and corners square.
7. Finished grooves shall be neat, of uniform width and depth, sharp straight edges and exact vertical and horizontal lines. Elevation grooves shall be cut before plaster sets by using molded guide or wooden strip and fixing it in temporary grout and screed. Regarding recessed, follow the procedures same as grooves.
8. Form cornices by plastering additional coats against pre-formed wood templates fixed onto plastered elevation. Make form wood templates to shapes, dimensions and projection indicated on drawings. Apply additional under coats in thickness not more that 10mm until obtaining required projection. Final finishes refer to item D.
9. 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 surface.

3. Curing

1. Provide sufficient moisture in the plaster by spraying water as frequently as required at least twice per day.

4. Cutting and Batching

A. Cut, patch, replace, repair and point up plaster as necessary      to       accommodate other work. Repair cracks and indented      surfaces.      Repair work to eliminate blisters, buckles,      check cracking, and dry out as necessary to comply          with visual effects.

B. To correct inaccuracies, dubbed out in thickness of not more      than   10mm in same mix as base coat and total thickness of

     dubbing must not exceed 25mm unless otherwise approved.

     In areas where thickness  is more than 20mm, apply dash

     keying mix before adding new layer.

C. To correct inaccuracies in beam, column together with block      work, chip carefully the concrete structures by using hammer      and chisel to receive dash coat (follow the procedure in 1.C).      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, start again same as from 1C.