Solid plastered surface application

interpret information and follow advice and understand principles of working on period properties

adopt safe working practices

select materials and components

prepare background surfaces for internal and external plasterwork finishes, following the style of the project

to include:

• old brickwork

  • joints raked out of approximately ¾ inch (19mm)

  • any smooth hard surfaces should be rough end by hacking or mechanical key

  • backgrounds providing no key should have a splatter dash coat applied to provide the key in an eminently hydraulic lime for a 2.5 -1 mix scratch coat.

  • background to be well brushed down to remove dust

  • scratch coat should be applied and allowed to cure a minimum of seven days

  • timber beams (lintels) should be checked for soundness and covered with wood or metal lathing (e-m-l) then counter battened or brandered and rendered approximately 7 days before new render is applied

• stone prep for renderer’s

  • background well brushed down with coarse broom

  • well wetted to control suction

  • joints well raked out

  • face of stone works to be roughened

  • apply the scratch coat as for old brickwork

• preparation of lathing

  • backgrounds (joists) should be checked for soundness

  • laths should be soaked 24 hours before fixing

  • lath breaks should be employed when fixing to avoid straight joints

  • laths should be fixed with the correct spacing between to allow for the mix to be pressed through to provide a secure key

  • before application of the mix laths should be mist sprayed to control the suction

  • the pricking up coat is applied diagonally across the lath background to ensure a good key is provided

  • when the prick coat is complete this coat is diagonally keyed to provide the key for succeeding coats

  • pricking up coat should be left for a minimum of two weeks and checked for hardness of the keys and between the laths prior to applying the floating coat

apply the floating coat with a devilled float to accept the final coat (left for a minimum of one week to enable the surface to firm up)

apply the finish coat and finished with a trowel, float, trowel operation to leave a good finish

work on conservation/restoration, repair and conversion projects

construct running moulds for in-situ work

cast from moulds in cement/sand/lime

setting jobs on site

identify differing types of backgrounds

to include:

• brickwork (handmade/pressed)

• blockwork

• breeze/clinker

• concrete (dense & lightweight)

• lignacite (sawdust/cement)

• keyed flettons (grooved to take plaster)

• terracotta hollow blocks (partition walling)

• sawn lathing

• split timber lathing

• e-m-l / rib lathing

• reeds

• cob

• chalk

• wattle

• straw, boards

control the suction of backgrounds

mix materials

protect existing surfaces as work proceeds

replicate traditional plaster finishes internally/externally

understand the principles and methods of setting out jobs on site

to include:

• drawings/detail/component/ assembly

• specifications

• preparation

• setting out procedures

• datum points (the purpose)

• starting points

• transferring datums

• the use of:

  • laser level

  • spirit level

  • water level

  • plumb bob and line

  • straight edge rule

  • box rule

  • flexible tape

  • surveyors tape

  • scale rule

prepare plasters coarse stuff/lime putty/plaster/cement/sands and additives

describe how to prepare surfaces appropriate to plasterwork finish

explain how to apply and finish internal and external plasterwork in one, two & three coat work

explain how surfaces are finished to the appropriate style and textured finish of existing

describe how to replicate textured finishes from a range of traditional work

explain how plasterers coarse stuff for first or pricking up coat on lathing is as below for masonry but gauged 1 – 2.5 by volume

describe how plasterers finish is mixed just prior to use and consists of lime putty and a fine washed sand gauged at approx 1 – 1 by volume. This can also be gauged on the spot board with a small amount of plaster of paris which improves the finish and helps avoid shrinkage cracking

describe what plasterers coarse stuff for first and second coats on masonry and second coat on lathing consists of

to include:

• lime putty to BS890 and hair

• well graded sand (aggregate) dry if possible

• gauge to 1-2.5 by volume

• excess water from mature lime putty is removed and saved

• the mature lime is placed into

• a pan mill and given an initial mix up

• the aggregate is then added gradually and well beaten in

• at this stage no water should be added

• the mixed coarse stuff should be stored in sealed bins or on banker boards covered with plastic sheeting until required, this mix of lime/aggregate matures with keeping

• coarse stuff should be re-worked before use by:

  • chopping as this will improve the workability

  • beating

  • ramming

explain how to prepare and mix lime putty

describe how to select sand/aggregates for mixing

explain the addition of pozzolanic additives such as brick dust and pulverised fuel ash when using lime putty mixes externally

describe alternative mixes using hydraulic lime instead of lime putty for external areas

explain NHL2. 3.5, 5.

describe the possible damage to lime plaster on lathing caused by vibrations/movement in structure caused by people working above whilst the material is in the early stages of carbonation

explain how to protect existing surfaces

explain how to protect flora and fauna

explain how to validate ways in which work should be carried out

explain how to maintain the main principles of minimum intervention on to the building/structure

explain how to select like for like materials

explain how to use like for like work techniques to match existing

describe how to record and survey work surfaces to be worked on, by photos and written reports

describe how to salvage and re-use existing materials

describe how to take sections from existing mouldings in-situ

describe how to construct running moulds for in-situ work

explain how to set up running rules for in-situ work

explain how to prepare moulds for cement/lime/sand casting

explain mix ratios for cement casting

to include:

• 3 – 1 for all o-p-c casting

• 3 well graded aggregate

• 1 ordinary Portland cement

describe how to select correct materials for casting

to include:

• sand (general building grade)

• granite chippings

• granite dust

• stone dust

• white cement

explain when to use the wet/dry method of cement casting

wet method:

• if using plaster moulds they will break down easily even when oiled and seasoned

• there is a problem of vibrating the mix in a plaster mould

• if the mix is not wet enough then the detail of the cast will not be produced as air will be trapped in the cast

semi-dry method:

• hollow casts can be produced

• the casting mix is tamped into the mould in layers of approx 40mm thick until the mould is completed

• the moulds used in this method can be used numerous times in a working day

explain the difference between restoration/conservation/repair and alteration