How To Skim or Plaster a wall.
Advice on plastering a wall from a qualified plasterer. The term 'skim' or 'skimming' a wall refers to laying a thin layer of finishing plaster to a wall or ceiling. The plaster layer is usually up to 3 mm thick, but will make the wall look refreshed and ready to receive new paint or wallpaper.
Skimming can only be performed on plasterboard, flat walls, painted, or prepared walls with a plaster scratch-coat underneath.
Skimming cannot be done on wood unless metal mesh ( EML ) has been attached over it, neither can metal be plastered over. Skimming over paper will end in disaster.
Professional plasterers can cost a fortune simply to plaster over a wall. The finishing plaster is relatively cheap, what you are paying for is the experience. Skimming a wall can be done by most people after a short practice.
One a plaster is mixed, there is approximately 30 minutes ( at best ) before it sets so much that it can longer be used. Any area to be plastered or skimmed has to be done within those 30 minutes.
Prior to skimming a wall, ensure that all tools and materials required are at hand.
Water bucket. Normal size.
Large hand brush. ( painting / pasting brush )
Mixing bucket. Large enough to hold mixed plaster
Mixing tool. This could be a drill with a paddle attachment.
Float. Marshalltown is typically the best. ( see opposite )
Hawk. Also called a hand board ( see opposite )
Bucket Trowel. Square Ended Trowel
These are the basic tools required. There are more which professionals use, but this lot is enough to skim a wall without going to to much expense.
Finishing plaster, PVA, water. The PVA is available where you purchase the plaster from.
Stage 1, Preparation Work
All finished work quality depends upon the preparation work quality. Small holes as big or bigger than the diameter of a cigarette should be filled with bonding or poly-filler. Any wall plugs can either be removed or hammered in to just below the surface of the wall.
Make a mix using the PVA. The mix is only to cover the are that you are skimming, so don't mix to much. The consistency should be 50% PVA and 50% water. Stir well then apply to the wall with the brush.
Ensure the wall is completely covered with the PVA mix. Brush out any drips as soon as possible because this stuff dries fast. Whilst the PVA is drying, begin to mix your plaster.
Stage 2, Mixing The Plaster
The water always goes into the bucket first. Remember, that the water will nearly double in size once the finishing plaster has been added, so use a large enough bucket.
Pour in finishing plaster until there is a mount in the middle of the bucket surrounded by water. Wet the end of the mixing tool or paddle before putting it into the bucket, this will prevent the plaster from sticking to it.
Keep adding finishing plaster to the mix whilst mixing until it is creamy. Eyes are deceptive, the mix may look quite creamy in the bucket, but could be very sloppy once it is taken out. Use the trowel to take a bit out and see how easy it falls off of the trowel. If it falls off with a wet splodge, then add a bit more finishing plaster and continue mixing.
The plaster needs to fall off of the trowel but seems stiff enough so as not to drip to much, but wet enough to spread.
Stage 3, Just Before You Start Plastering
Before attempting to get the plaster onto the wall, touch the PVA should be slightly tacky to nearly dry to the touch.
If you are right handed, you will be starting on the left side of the wall. For left handed people, start on the right side of the wall. This sounds strange but it works very well.
Use the bucket trowel to get the plaster out of the bucket. Start with about 1.5 dollops onto the hawk board.
Whilst holding your float before putting plaster on it, put your arm outwards towards the wall. Hold the float so as the face ( the bit where the plaster will go onto ) is parallel to the wall with the back of your hand facing the ceiling. This is the way you are going to plaster most of the wall.
Stage 4, Getting Plaster on the Wall
Get about half of the plaster from the hawk onto the float. If you are new to this, most of it will end up on the floor for the first few attempts. Hold the float at an angle of approximately 45 degrees. Begin to spread the plaster up the wall.
Allow the plaster to spread easily. There needs to be 3mm depth or less on the wall. Spread in a candy cone shape as far up the wall as you can easily reach. DO NOT go over it again with the float, not yet. Put some more plaster onto the haw and repeat the process. BUT.. this time, allow the float to part overlap the plaster from the first stroke.
Congratulations, you are now a fully qualified plasterer, sit down and have a cup of tea. NO, DON'T.
Once you have done two strokes with the float and got some plaster on the wall, use the trowel with no plaster on it and lightly go over the two strokes you have done. Do not worry if there are holes or lines left in the plaster on the wall. The main purpose of this first coat is to get the plaster onto the wall.
Continue along the wall in the same fashion until you are approximately 24 inches from the end of the wall.
Stage 5, The Corners
You are now only 24 inches away from an internal corner and the bottom 3/4 of the wall has been smeared with plaster. Have some plaster on the float, and start from the corner of the wall going horizontal ( side ways ). Do this is the same method as applying the rest of the plaster, but across ways instead of upwards.
Only bring the plaster side ways until it slightly overlaps or touches the upward stroked plaster.
Do this all the way up the wall so as the whole corner is covered. No get onto the step ladders and get ready to plaster / skim the top part of the wall. This is to be done with little plaster on the float, but in downward strokes. Again only do until you reach and slightly overlap the end of the upward strokes.
All trowels, hawks and floats etc, should be wet before the plaster mix touches it.
Different plasterers find different methods that suit them best after a few practices.
Stage 6, Second Coat
This is not a proper second coat. It is merely a small amount of plaster on the float which is only for filling in any holes in the first coat. Start from where you originally began and continue this pattern until the second coat is on. First touch the plaster, if it is still tacky, wait a while. if you do not leave a fingerprint, then it is time to add the second coat.
The second coat is to lose any lines and fill hollows left by the first coat. Try to get it as smooth as possible. But if not, at this stage, do not worry to much, just a little.
Stage 7, Wet Troweling
Use the brush to add water to the edge of the wall, or use a spray gun and add a few sprays to where you will be working. Do not add too much water as it may leave streaks.
Take the empty trowel, which you will now systematically wash with plain water every few strokes or so. Trowel along the plaster from left to right, the whole length of the wall. This will smooth out bumps and what is called 'fat' will be left on the trowel. This 'fat' is no good, just wipe or brush it off. ( although some people use it to fill in small dents ).
Wet trowel the wall twice, leaving about 4 - 5 minutes between each one.
Plastering Over Paint
First remove all loose and flaky bits of paint from the wall or ceiling using a scraper. Coat the wall with a PVA solution.
Once the PVA has become tacky (nearly dry) then begin skimming over the paint with multi finish plaster.
You have just plastered your first wall. You may find most plaster is on the floor, clean this up before your partner goes nuts. Wash all tools and put in the loft or shed for ever or until you have a clear out and sell them on ebay.
If you have any questions, or need advice or help on plastering, please use the comment box below and leave an email address so as I can message you back. The email address will not be shown on this site.
Free links to:
Dry Lining - How to plasterboard walls and ceilings easily.
Rendering - How to render internal and external walls
billericky (author) from Plymouth on October 04, 2012:
Hollows are relatively simple to obliterate. Use a very small amount of finishing plaster, even the 'fat' can be used, and lightly go over the hollow with the float. The hollow should then be filled.
If the scuff marks are where the trowel/float gently bounces across the wall or ceiling and leaves like small ridges, this is called 'chattering'. Simply float over again adding a bit more pressure, that should remove them. Try using the float at a slightly different angle.
If the scuff marks are made by the edge of the trowel, this is unfortunate, but a little bit of patience and practice overcomes this problem.
dave.f on October 03, 2012:
Hi I keep leaving like hollows or scuffs when skimming any tips please.