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How to plaster - hints and tips

How to get the best results when using the British Gypsum Thistle Plaster range

At British Gypsum we believe our products will provide you and your customers with the perfect plastering experience. To help you get there follow this guide for tips and hints on how to get that dream finish and get the most from our products.

Plasterer plastering a wall with Thistle Plaster products

 

Step 1

  Tools for the job   

       


 Step 2

  Surface preparation   

       


 Step 3

   Mixing the plaster   

       


 Step 4

  Application   

       


 Step 5

 Decoration and tiling 


See our range of tailored how to videos for instructional advice on how to apply British Gypsum products such as Thistle Magnetic Plaster - turning any wall interactive or Gyproc Habito - our strongest most durable plasterboard.



1. You will need:


Two - coat plastering:
         Skimming:
  •  Clean bucket
 
  •  Clean bucket
  •  Mechanical whisk
 
  •  Mechanical whisk
  •  Gyproc Bucket trowel
 
  •  Gyproc Bucket trowel
  •  Gyproc Hawk
 
  •  Gyproc Hawk
  •  Finishing trowel
 
  •  Finishing trowel
  •  Solid plastering beads    
 
  •  Water
 
  •  Water
   
     

2.  Before you start, the background should be

  • Protected from the weather, with no risk of freezing
  • Adequately strong, rigid and stable
  • Clean and free of dust, shutter release agents, etc.
  • Reasonably dry
  • Free of salt efflorescence

Surface pre-treatment


See plaster selector chart for details



3.  Mixing the plaster

  • All mixing equipment should be cleaned before use to prevent contamination.
  • Pour the required amount of water into the mixing bucket (see selector chart for details). Only add clean water and do not use any additives.
  • Add plaster to the water and mix by hand or a slow speed, high torque mechanical whisk. 
  • Thistle plasters should be mixed to a smooth creamy consistency. There is no need to continue mixing after lumps have been dispersed. Over mixing can affect setting times and cause difficulty in achieving a flat finish.


4.  Application

  • Check the use-by date on the bags, making sure you use the oldest material first.
  • Ensure the room temperature is controlled. Plaster should not be applied to frozen backgrounds or in very hot or dry conditions.
  • Sequence the work. Setting time is approximately 90 minutes, but finishing times can be extended in low temperatures by 30 minutes or more.
  • Do not mix more than you’ll be able to use, we suggest a maximum of two bags.



Two - coat plastering:
       Skim plastering:
  • For corner reinforcement fix beads to all external angles using undercoat plaster.
 
  • For corner reinforcement fix beads to all external angles.
     
  • Reinforce all plasterboard joints and internal angles by using Thistle ProTape or Gyproc Joint Tape. Gyproc Joint Tape will provide greater resistance to cracking particularly when board edges are not fully supported.
 
  • Apply plaster with firm pressure after the joint treatment has stiffened but not set, building out to approximately 8mm thickness.
   
  • Apply plaster with firm pressure after the joint treatment has stiffened but not set, to approximately 1mm thickness.
 
  • Scratch each coat and allow to set before applying the next.
   
  • Apply a second coat of plaster whilst the first coat is still wet to bring the total thickness to 2mm.
 
  • The maximum thickness of undercoat plaster is 25mm. Greater thicknesses will require additional support, such as metal lathing, spaced away from the background if necessary.
   
  • Trowel to a smooth matt finish as the plaster is stiffening.
 
  • Rule the final coat to an even surface and lightly scratch to form a key for finish coat plasters.
   
  • Use any additional water sparingly and only in the latter stages of trowelling.


See our range of tailored how to videos for instructional advice on how to apply British Gypsum products such as Thistle Magnetic Plaster - turning any wall interactive or Gyproc Habito - our strongest most durable plasterboard.


5.  Decoration & tiling

  • Thistle plasters can be decorated with most paint finishes and wall coverings by following the manufacturers’ recommendations.
  • Impermeable finishes, such as tiles, should not be applied until the background and plaster are dry.
  • Take care with Thistle HardWall and Thistle ToughCoat which dry from the surface, appearing surface dry before they are fully dry.
  • Tiles up to 20kg/m2 can be applied directly to Thistle finish coats. If a bonding agent is used the limit is reduced to 12kg/m.2
  • Tiles should not be applied directly to Thistle undercoats, with the exception of Thistle DriCoat.
  • Where tiling onto finish plasters, avoid polishing the surface.  Where the surface is polished, roughen and apply a suitable primer.

Re-plastering following a damp proof course treatment
  • British Gypsum only recommends Thistle DriCoat
  • Identify and eliminate the source of penetrating and rising damp before any work is undertaken.
  • Existing plasterwork should be removed to at least 0.5 metres above the new damp proof course, or the highest detectable sign of dampness.
  • Allow curing and shrinkage of Thistle DriCoat, then scratch ready for application of Thistle Board Finish plaster.
  • Never bridge a damp proof course.
  • Coverage of Thistle Dri-Coat is approximately 3.25m² per bag, when applied at 11mm thickness.

Coverage Calculator

Unsure on the amount of plaster you need for your project? Use our Plaster Coverage Calculator to estimate the surface area and number of plaster bags required for your project. In order to start you will need to know the height and width of each wall, ceiling or area you intend to cover.

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