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IntroductionGyproc Floating Coat and Base Coat Plasters have beendeveloped in response to a demand for a high convenience,dependable, hard, gypsum base coat plaster providing ahigh compressive strength and impact resistance. They arespecifically designed for use on concrete block backgroundsand should not be applied to plasterboard.

Gyproc Floating Coat and Base Coat are manufacturedfrom retarded hemihydrate gypsum.

Reaction to FireThe plasters are non-combustible when tested inaccordance with BS 476: Part 4 1970 (Amended 1984). Forthe purpose of the Building Regulations 1997,(TechnicalGuidance Document B) gypsum plasters are designatednon-combustible materials. Gypsum plasters also satisfy therequirements for Class O surfaces.

Effect of TemperatureIt is recommended that the background temperatureshould be at least 5ºC and that the plaster should not besubjected to temperatures below 5ºC before it has set. Drybagged plaster is not affected by low temperatures.

The plaster is not suitable for use in situations where thetemperature exceeds 43°C.

StorageThe plaster should be stored dry, as the absorption ofmoisture by any gypsum plaster shortens the setting timeand may reduce the strength of the set plaster. Wherestorage areas have concrete floors, timber platforms shouldbe laid and the plaster stored on these. The shelf life ofGyproc Floating Coat and Base Coat is 12 weeks.

MixingGyproc Floating Coat and Base Coat plasters are premixedwith aggregate and only clean water need be added toprepare it for use. No admixtures should be used. Mix to anormal plastering consistency. Cleanliness is essential, setplaster left in a receptacle from a previous mixing willshorten the setting time. This can reduce the strength ofthe plaster when set. Mixing trays and buckets must bewashed thoroughly after each mix. Mechanical mixing maybe used, but care should be taken not to mix throughthe set.

ApplicationDry blockwork should be well brushed down to remove anydust or loose particles of mortar etc. from the surface. Anymetal objects such as nails etc. should be removed from theface and blockwork should be well wetted to off-setexcessive suction in the background. Plaster of the correctconsistency should be applied with very firm pressure andthe Gyproc Floating Coat or Base Coat brought to a trueand level surface by means of a straight edge or darby.

The surface should be closed with a hand float andthoroughly scratched to provide a key for the finishingcoat. Never attempt to retemper Gyproc Floating Coat orBase Coat Plaster after the set has commenced.

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Approximate CoverageGyproc Floating Coat plaster applied to a nominal thicknessof 10mm will give an approximate coverage of 117m2 pertonne*. Gyproc Base Coat plaster applied to a nominalthickness of 10mm will give an approximate coverage of102m2 per tonne*. See Plastering Specifications,section .

*Depending on the straightness of the concrete blockwork.

Setting Time3 to 5 hours, depending on background suction andenvironmental conditions.

Projection PlasterGyproc Floating Coat, subject to suitable conditions anduse of appropriate equipment, may be suitable for use as abasecoat projection plaster. A finish coat plaster of GyprocSkimcoat or Carlite Finish should be applied.

FinishingA finishing coat of Gyproc Skimcoat or Carlite Finish can beapplied as soon as the Floating Coat or Base Coat has set.The finish plaster should be applied to a nominal thicknessof 2mm and trowelled to provide a smooth finish.

Finishing coat coverage at 2mm thickness is 375m2 pertonne. See Plastering Specifications, section .

Drying Adequate ventilation is an essential requirement to aiddrying out of all plasters. In accordance with I.S. CEN/TR15124:2005 ‘when the application is finished Gypsumplastering should be ventilated until it has dried.’

In addition, I.S. EN13914-2:2005 states that ‘if adequateventilation is not provided during the drying of the plaster,then the strength of the plaster may be impaired and thetime at which decoration may start may be delayed.’

Decoration Follow normal procedures and techniques.

Party Wall Sound RegulationsTechnical Guidance Document E, Sound, 1997, providesseveral specifications for solid masonry sound insulatingwalls. Wall specification A is as follows:

Typically the required mass (415 kg/m2) can be achieved bya 5N common block (must be confirmed by the blockmanufacturer).

11mm Gyproc Floating Coat or Base Coat, finished with2mm of Gyproc Skimcoat or Carlite Finish is a suitableplaster finish to each side of the blockwork wall. The use ofGyproc Floating Coat or Base Coat instead of the‘traditional’ sand and cement allows earlier application ofthe finish coat plaster.

Site sound test results are shown below:

These results are well in excess of the values in Table 1

of Technical Guidance Document E, 1997. Please contact

us if you wish to obtain a copy of the sound insulation

test reports.

Air PermeabilityPlastering a blockwork wall with Gyproc Base Coat or

Floating Coat finished with Gyproc Skim Coat or Carlite

Finish will aid compliance with the air permeability

requirements listed in Technical Guidance Document L,

Conservation of Fuel and Energy, Dwellings, 2007

(implemented 1st July 2008).

A concrete blockwork or concrete brickwork plastered onboth faces

The average mass of the wall (including theplaster) should be at least 415kg/m2.

The thickness of the plaster should be at least12.5mm on each face.

Use blocks which extend to the full thickness of thewall, i.e. blocks laid on their flat.

Example215mm solid concrete block, 112.5mm coursing,lightweight plaster; block density of 1860 kg/m3

gives the required mass.

1.11

1.11

Result Mean(dB DnT,w) (dB DnT,w)

Site A 56, 57, 55, 56 56

Site B 58, 57, 57, 58 57.5

Site C 54, 61, 54, 57 57

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IntroductionGyproc Bonding Plaster is one of the range of lightweight,retarded hemihydrate, premixed gypsum plasters, requiringonly the addition of clean water to prepare them for use.Gyproc Bonding is a base coat for low suction backgrounds.

Reaction to FireThe plasters are non-combustible when tested inaccordance with BS 476: Part 4 1970 (Amended 1984). Forthe purpose of the Building Regulations 1997, gypsumplasters are designated non-combustible materials,(Technical Guidance Document B). Gypsum plasters alsosatisfy the requirements for Class O surfaces.

Effect of TemperatureIt is recommended that the background temperatureshould be at least 5ºC and that the plaster should not besubjected to temperatures below 5ºC before it has set. Drybagged plaster is not affected by low temperatures.

The plaster is not suitable for use in situations where thetemperature exceeds 43°C.

StorageThe plaster should be stored dry, as the absorption ofmoisture by any gypsum plaster shortens the setting timeand may reduce the strength of the set plaster. Wherestorage areas have concrete floors, timber platforms shouldbe laid and the plaster stored on these. The shelf life ofGyproc Bonding is 12 weeks.

MixingMix to normal plastering consistency using clean waterdrawn directly from a tap or hydrant. No admixturesshould be used. Cleanliness is essential. Set plaster left in areceptacle from a previous mix will shorten the setting timeand may reduce the strength of the plaster when set.Mixing trays and buckets must be washed thoroughly aftereach mix. Mechanical mixing may be used, but care shouldbe taken not to mix through the set.

ApplicationGyproc PlasterboardsGyproc Bonding should be applied to the grey face ofGyproc Wallboards, 4x2’s, 8x2’s, Round Edge Greyboardsand Plank at a thickness of 10mm.

In-situ concretePlastering over in-situ concrete has long been regarded asone of the plastering trade’s most complex problems.Depending on mix, aggregates, chemical additives,vibrating and shuttering, the surface of concrete can varyfrom one contract to another and cannot, therefore, beconsidered a consistent background for plastering. A verysmoothly finished concrete can inhibit good adhesion ofthe plaster, as can concrete with a very high suction. Theshearing force set up by the differential expansionbetween plaster and concrete can cause loss of adhesion ofthe plaster. The formulation of a plaster capable of dealingwith all combinations of these factors has so far not beenachieved. However, experience over many years has shownthat once the concrete surface is clean and free of all dust,mold-oil or other release agents the following methodsmay be suitable:

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(a) the application of ThistleBond-it in accordance withsection or

(b) the application of Gyproc Bonding over a scudcoatincorporating an S.B.R. bonding agent, applied as perthe bonding agent manufacturer’s instructions*.

*Scud Coat: Tests have indicated that best results areobtained when a latex modified mortar of sand, cementand a proprietary bonding agent such as Evo-Fix, orequivalent, is applied as a scud coat. Such modified mortarshould be prepared strictly in accordance with theinstructions of the bonding agent manufacturer. It isreiterated that the concrete surface should be cleaneddown and be free of all dust, mould-oil, or otherrelease agents.

Gyproc Bonding should normally be applied to a thicknessof 10mm. The coat should not be thicker than is necessaryto bring the work to a level surface, particularly on soffits.The plaster must not be mixed to a softer consistency thannormal in an effort to apply a very thin coat since theadditional water used will reduce the strength of theplaster. With thin coats there is also a risk of dry out.

Gyproc Bonding should be trowelled tightly with firmpressure, built out to the required thickness, ruled to aneven surface and properly scratched to form a key for thefinishing coat of Carlite Finish or Gyproc Skimcoat Plaster.

Setting Time3 to 4 hours, but may be affected by background suctionand environmental conditions.

Drying Adequate ventilation is an essential requirement to aiddrying out of all plasters. In accordance with I.S. CEN/TR15124:2005 ‘when the application is finished Gypsumplastering should be ventilated until it has dried.’

In addition, I.S. EN13914-2:2005 states that ‘if adequateventilation is not provided during the drying of the plaster,then the strength of the plaster may be impaired and thetime at which decoration may start may be delayed.’

DurabilityGyproc Bonding Plaster with a final coat of 2mm CarliteFinish or Gyproc Skimcoat provides a plastering systemsuitable for moderate to high impact/wear areas.

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