How to apply a 2-coat plaster | British Gypsum

How to apply a 2-coat plaster | British Gypsum


Before we start to apply the product,
it’s worth noting the important information on the bag. Down the side of
the bag you’ll find a use by date. Make sure the plaster is within date, as
after this date the plaster may not perform as it should in terms of
workability or set times. Before applying an undercoat plaster, in this case Thistle HardWall, it is important to check that the background is suitable by
referring to our latest technical information, and that any preparation has
taken place. As part of the background preparation, all 2 coat plaster angle
beads should be fixed in position using Thistle plaster. In this case
Thistle MultiFinish, once applied and lined in, the angle
beads should be left to set before you start to apply Thistle HardWall. When
mixing the plaster always add the powder to clean cold water. Keep adding powder
to the water and mix to the required consistency. Using a stainless steel
trowel apply the first coat of plaster to the background. You’ll notice that our
undercoat plaster is grey. This is because of where the rock is mined, and
it helps our demonstration of the different plaster layers. Once the entire
background has been covered, a second thin coat of plaster should be applied
over the whole surface. Once the required thickness of plaster has been applied,
the wall can be ruled off with a darby, serrated straight edge or feather edge,
and any low or hollow spots that have been missed during the application
process can be filled. When you’re not applying Thistle undercoat plaster to a
wall with a window or door in it, a broad screed system can be used as
demonstrated here… Apply the material vertically on the wall, making the screeds a trowel width and to the correct thickness, this process would be repeated
on the opposite side of the wall, the area between the screeds would then be
filled in with plaster before ruling off with a straight edge to produce a flat
wall. Where a long wall is being plastered, the screeds would be set at a distance to suit the straight edge. Once the wall is leveled a spatula should be
used to close and flatten the surface of the plaster. Once it has started to pick
up, go over the surface with a devil float to provide a mechanical key for
the finish coat plaster. Now the plaster is set we’re ready to
mix and apply the finish coat plaster. Don’t forget to check the use by date. We are using Thistle MultiFinish over
the Thistle HardWall undercoat plaster to achieve a flat smooth surface. The
first coat of finish plaster is applied to the wall. After allowing the first coat to take
in, a further second coat is applied to obtain a smooth finish. A number of further trowel applications
are needed to obtain the finish required. There you have it! A solid plastered wall
ready in no time

9 Replies to “How to apply a 2-coat plaster | British Gypsum”

  1. What is the surface background there ? I thought that Multi-Finish only adheres to plasterboard, PVA over old Plaster, Undercoat plaster or render and also smooth Concrete with a Bonding Agent and a Painted background ? is the wall smooth Concrete ? with a bonding agent used for the beads ? I noticed the beaded area is applied with Multi-Finish ? what is the back ground surface ? because has a Plasterer preparing the back-ground surface is key ? i would have used Undercoat Plaster HardWall for the beads , prepared with Water ? Then cutback the beads the next day or the same day and then apply the Skim Coat the next day u could use water for adhesion ?

  2. It's interesting watching the different methods of application of plasters. My first trowel is the top-half of the wall – vertically, and then join-in along the bottom, again vertically. Pulling horizontally along top and bottom every so often only to check for scoops/misses. I have seen far more random plastering, and the finished item most certainly felt like it. The multifinish for beads does indeed seem unusual, as there is Hardwall/Bonding for basecoats. Also, as there was a mixed, damaged, and dry background, it was not wetted down, or had pva, or grit adhesive applied.

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