Application - Why are 2 coats needed?
2 coats doubles your chances of success.
Flatness is a lot easier to achieve with two thin coats rather than one thick coat. The first coat will often not be perfectly flat and may have blemishes - let this coat firm up and then the second will not be able to push it out of shape and a greater flatness can be achieved. 'Trowelling up' can only commence when the plaster is firm enough – some ares of the wall may be drying at different rates, but trowelling up different areas of the wall at different times may result in a sub standard finish. Allowing the first coat firm up over the entire wall before applying the 2nd coat minimises any drying differences on the wall
The skim coat should be applied in a grid system.
This provides a methodical way of working across the wall ensuring you can cover the wall in an efficient manner. The first section to complete is the top border. This enables you to concentrate on keeping the plaster flat right into the corner.
Load plaster onto trowel.
Take trowel to wall, on the top line, keeping it flat to the floor.
Then you will gradually start to turn your trowel so that it is nearly vertical so that you can take it from left to right across the wall. As you do this you will gradually flatten your trowel closer and closer to the wall as the amount of plaster reduces from your trowel. When there is no remaining plaster left on your trowel you can then ease it off the wall and place it back on again with the leading edge switched as you will now be going from right to left to flatten the plaster you've just applied.
Do remember that to flatten the leading of your trowel will be approx 10 – 15mm away from the wall. Do this until you have an even thickness of 1-2mm. Before we move on you need to load a small amount of plaster on the relevant edge of your trowel so that you can apply plaster right into the top of the wall where it meets the ceiling. This can then be flattened just as before by long sweeping movements with your trowel. (long sweeping strokes should always be used throughout the whole skimming process).
Particular attention should be paid to all the corners to ensure they are not bulging.
The procedure listed above and below is relevant for stages 1&3. For the other stages the trowel strokes are the same but noplaster will be applied – your trowel will be flatter to the wall and used for flattening/smoothing the plaster
Always ensure the corners / edges of the wall are kept flat. If the wall next to theone you are plastering is porous then wetting the corner will ensure the plaster doesn't dry too quickly as a result of being in contact with a porous surface.
Load plaster on trowel
Take trowel to mid line keeping it flat to the floor – as the amount of plaster on your trowel reduces begin to flatten it in closer and closer to the wall. As you approach the top line turn your trowel round through 90 degrees and continue until you're in the next section.
Care should be taken to ensure that the correct flatness of your trowel is maintained and that the top edge of your trowel just overlaps the top section but is kept firmly on it and not double coating it.
Then ease your trowel off the wall and place it back on again with the leading edge switched so that you can carry out the procedure again but in reverse. The plaster has been applied so this stroke will be responsible for flattening – therefore a constant 10-15mm leading edge of your trowel combined with firm pressure will push all the highs into the lows. Repeat this process a couple of times as needed. You should be aware of the different stages of skimming and what is required for each stage. Don't keep going over and over the same area relentlessly in the pursuit of perfection in the early stages as you will just get frustrated. When section 2 has been completed then repeat the process for the remaining middle sections.
The method for the bottom of the wall should be exactly the same as for the middle section. When you join up with the plaster at the mid line your trowel should be turned just as when you met up with the top section, to ensure the middle section is not double coated. Do not apply plaster right at the bottom of the wall – leave a gap of approximately 50mm. This will prevent you from picking up grit from the floor. This gap will be covered by skirting board. If there will be no skirting board then the floor should be swept and particular attention should be paid when applying plaster to ensure that it doesn't bulge right at the bottom of the wall.
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The author cannot accept liability for the use of any of the materials or methods recommended in this manual or for any consequences arising out of their use. The author cannot guarantee the suitability of any recommendations made in this manual and shall not be under any legal liability of any kind in respect of or arising out of the content of this guide.