PLASTERING

   PLASTERING

                LIME PLASTERS – 15 MM THICK:

                The plaster shall not exceed 15 mm total thickness. This shall consist of a single 

                coat of lime mortar including where necessary the setting coat of pure white lime 

                putty.

 

Plaster

                MATERIALS:

                Lime mortar 1:2 or other specified proportion conforming to the requirements of 

                Clause 3.1.

               SURFACE PREPARATION:

New  brickwork  or  stone  masonry  shall  have  been  finished  with  recessed  joints  to  receive  plastering

see clauses 6.2.7 and 7.2.3 respectively. In the case of stone masonry, the bushings on the wall to be

plastered, shall be removed to within 12 mm projection.

                Where so specified for dense and smooth surfaces a suitable bonding treatment 

                shall be applied to manufacturers instructions before plastering.

                All soft joints in old stone masonry or brick work shall be ranked out to a depth of 

                not less than 12 mm.

                The walls shall be brushed clean of all dust, thoroughly wetted and surface dried 

                before plaster is applied.

               APPLICATION: 

Plastering of walls shall commence after completion of ceiling plastering if any. The plastering shall be

started  from  the  top  and  worked  down  towards  the  floor.  All  putͲlogͲholes  (i.e.  holes  left  for

scaffolding) shall be properly filled in advance of the plastering.

To ensure an even thickness and a true surface, gauges of plaster 15 mm x 15 mm, or broken clay tiles

set in mortar shall be first established on the entire surface at about 2 metre intervals both vertically

and horizontally.

The  thickness  of  the  plaster  specified  excludes  the  key  i.e.  the  grooves  or  open  joints  in  the  brick

work.

The minimum thickness of the plaster over any portion of the surface shall not vary from the specified

thickness by more than 3 mm.

Mortar  shall  be  applied  between  the  gauges  to  slightly  more  thant  he  require  thickness  i.e.  slightly

proud of the gauges. The plaster shall be well pressed into the joints, levelled and brought to a true surface by working on a wooden straight edge reaching across gauges, with small upward and sideways movement. Finally the surface shall be finished true with a wood float or trowel according to the type of finish required.

If a sandy granular texture is needed, the surface shall be wood floated. If a smooth finish is needed,

trowelling  shall  be  done  to  the  extend  required;  during  this  process  the  setting  coat  of  pure  white

lime putty shall be applied on the surface to facilitate finishing.

All  moulded  work,  apart  from  the  cover  shall  be  formed  and  run  in  lime  cement  mortar  1:1:15  all

ornaments, mitres etc. neatly formed. These shall be finished with lime putty as described above.

All arrises shall be plastered in lime cement mortar 1:1:15 and finished with lime putty for wedges of

not less than 25 mm along each face of the arris.

All necessary dubbing behind, rounding of  corners at the junctions of the walls plastering of cornices

etc. shall be done.

In  suspending  work  at  the  end  of  the  day,  the  plaster  shall  be  left  cut  clean  to  line  both  horizontally

and vertically. When recommencing the plastering, the edge of the old work shall be scraped, cleaned and wetted with lime putty before plaster is applied to the adjacent areas, to enable the tow to be properly jointed together. Plastering work shall be closed at the end of the day on the body of the wall not nearer than 150 mm to any corners or arrises. It shall not be closed on the body of features such as plaster band and cornices, nor at corners or arrises.

Horizontal joints in plaster work shall not be formed on parapet tops and copings, as these invariably

lead to leakages.

No portion of the surface shall be left out initially to be patched up later on.

Any cracks which appear on the surface and all portions which sound hollow when tapped, or are found to be soft or otherwise defective shall be cut out in rectangular shape and redone as directed by the officerͲinͲcharge.

               FINISH:

The  plaster  shall  be  finished  to  a  true  and  plumb  surface  and  to  the  degree  of  smoothness  required.

The work shall be tested frequently as the work proceeds with a true straight edge not less than 2.5m long and with plumb bobs. The gap between the straight edge and any point on the plastered surface shall not exceed 3 mm. All horizontal lines and surface shall be tested with a level and all jambs and corners with a plumb bob as the work proceeds.

                       CURING:

Curing shall be started 24 hours after finishing the plaster. The plaster shall be kept wet for a period of seven days. During this period it shall be suitably protected for all damages, at the contractor’s expense by such means as the officerͲinͲcharge may approve.