How to Plaster - Techniques - How to skim on to plasterboard.
Always skim in two plaster coats.
Plaster coat one is roughing on and plaster coat two is laying down.
Roughing on Plaster coat should be about 3mm thick, even and relatively flat. Plastering trowelling lines will be blended into the laying down plaster coat which will be up to 2mm thick. Avoid leaving thin areas of roughing on plaster coat as this will effect the trowelling process. Ensure that the laying down plaster coat covers the whole plasterboard wall also as this too will effect the trowelling process and quality of plaster scim finish.
The laying down plaster coat should ideally not be the same plaster mix as any part of the roughing on plaster coat.
Apply plastering scrim tape to plasterboard joints and drywall screw heads.
Prepare your plastering tools, plastering materials and work area.
Mix your plastering skim be it board finish plaster or multifinish plaster.
Place the plaster on the spot board and clean your bucket ready for the next plaster mix.
You now have up to 15 minutes to apply the plaster to the plasterboard wall.
Load your plasterers trowel with an amount of plaster that is going to give an efficient and wide covering of plaster.
Remember to use the “pattern of three”. i.e. divide you wall into 3 horizontal sections. Plaster the top 1/3 first from top left to bottom right of the 1/3. Then move down to the middle 1/3 of the wall again top left to bottom right of the section.
Then plaster the bottom 1/3 of the wall similarly.
If you are left handed, reverse left and right above.
The pattern of three is important to help you maintain control of your plasterboard wall. It helps to produce predictable plastering outcomes as you will be able to predict in what order the plaster is going to harden across the wall and follow that process with your trowelling.
The pattern of three also enables you to predict where the state of plaster is going to change in the event that you have to introduce a new plaster mix in order to complete a coat of plaster
Apply a skim of plaster over each of the plasterboard joint and scim or angle beads that are on the plasterboard wall.
Start in the top left hand corner of the wall and pull the plaster in from the side. Then start to pull plaster down from the top.
Ensure that you go to the wall with care ensuring that the smoothing edge of the plasterers trowel is in contact with the plasterboard wall before starting to apply the plaster. Remember that this prevents lumps and ridges being produced in the middle of the plastered wall and enables the internal corners to be tight and clean.
Now fill in the area of plasterboard that you have not covered in plaster.
Now move along the wall and pull down and fill.
Keep your plasterers trowel well loaded at all times.
Apply sufficient pressure with the plasterers trowel to ensure that you are flattening the plaster as it is applied to the plasterboard wall and not leaving “cats’ eyes” or holes.
If you hear the plasterers trowel scraping across the plasterboard stop! You are not applying plaster. You should always here the “squelch” of the plaster between plasterboard and plasterers trowel to know that you are applying plaster.
If a passage of the plasterers trowel leaves uncovered areas of plasterboard do not keep going over the same spot unless you have reloaded you plasterers trowel with plaster.
Do not stand back and admire you handy work until the wall is fully and evenly covered.
Do not dwell on smoothing areas of the wall until you have the whole wall covered in plaster.
Always plaster into plaster rather than plastering out of plaster as this will help prevent ridges across the wall.
If you think that a wall will be too big to tackle in a single session then use the scrim tape method of dividing the wall and seamlessly feather in sections of the wall.
When plastering the bottom of the all where the skirting board is going to be fixed always ensure that the surface is flat and not full of raised areas of plaster that the skirting board will “rock on”
Do not plaster right down to the bottom of the plasterboard. Leave up to 1” unplastered behind where the skirting board will be fixed. This will prevent the edge of the plasterboard causing dragging in the trowelling process.
Once you have completed the roughing on plaster coat, IF NECESSARY, go over it ONCE only with your plasterers trowel to get out any big problems that a novice plasterer may have left. DO NOT trowel it more than once on any part of the wall. You risk wasting time, causing blistering and preventing the laying down plaster coat from taking.
Using clean water, mix your laying down plaster coat.
Following the same rules as above apply the laying down plaster coat.
Ensure that you cover every part of the plasterboardwall. The “pattern of 3” will help you to achieve this.
By following the “pattern of 3” you will find that when you get to the bottom right corner of the wall, the roughing on plaster coat will be in the same state as when you started the top left part of the wall.
Once you have applied the laying down plaster coat you will be ready to start the trowelling process.