Skimming – The art of flat walls.

It’s a nice meaty blog for you this time at MrFixingIt.co.uk, all about plastering and techniques to do so.
Some people consider plastering an art that you must go to college to learn or to study. But I always think if you can’t offer the information to everybody, how is anybody going to carry on learning if they didn’t go to college just for plastering? A skim is a coat of two very thin layers of plaster placed upon each other to create a very smooth and flattened out finished layer. Whilst this sounds easy in concept it is more difficult in practice.
Preparing is always the very first thing that must be done before any task is taken to hand. The wall must be coated in a watered down PVA, a mixture of five parts water one part PVA can be sufficient, but other people prefer a 3-1. Use which ever seems better to you, even though the lower content of water is essential to high suction backgrounds. Use a large brush and begin at the top when applying your new mixture, the reason for starting at the top is that the mixture will drip down and you must catch up with it with the brush to make a nice even coat of PVA. Don’t be afraid to apply the PVA generously. This preparation step ensures there is good connection between the plaster and the wall for application. Wait until the PVA becomes slightly tacky but not full hardened, however if it does harden and hasn’t been left longer than 24 hours this is not a problem as the moisture in the plaster will cause the PVA to become tacky once again.
Now you have moved on to applying the plaster, the first thing you must know is that the first layer of plaster is to ensure that the wall is as flat as possible to then use the second coat as the finish, aim for a thickness of about 2mm on the first coat. Powdered plaster can be purchased at places such as B&Q or Homebase, you can find links to these stores in our affiliation page. Mix enough plaster for one wall, by pouring powder into the bucket and adding in water every now and then until you get a nice consistency, this should be about the same consistency as melted ice cream. A great tool to use to mix plaster is a drill with a paddle fitted, it takes a lot of the effort out of the mixing process.
A hawk must be used to get the plaster from the bucket to the trowel. This process is quite tricky and daunting but it can be made easier by following this procedure. Scoop three generous scoops of plaster upon the hawk using the bucket or any other tool of your choice, that was the easy bit. Getting the plaster from the hawk to the trowel is the more tricky part, its all to do with movement of the hawk and the trowel together as the plaster is designed not to run at an angle. Hold the trowel so the base is facing upwards and tilt the hawk towards the trowel until at a 45° angle, begin scooping and take small layers of plaster at a time upon to the trowel as to not overload it too quickly.
Trowelling is the stage that will make a mess on the floor if you have never tried it before, so its a good idea to protect the floor. To begin with, with a loaded trowel, continue to hold the trowel facing upwards and you may do the same with the hawk underneath to catch any falling plaster. Now gradually begin to tilt the trowel to touch the wall until there is contact. Now you are contacted move the trowel down the wall and then back up again to smooth out and make a nice flat layer, continue to do this in the same manner until you have layered the wall once. Remember to brush out your lines as you go with a nice 4″ brush. Continue to work into the wall until you have made it level and flat.
The final layer is the most difficult and takes quite some time to get right as it takes a lot more trowel control. This layer essentially should be much thinner, using less plaster than the first and being only around 1mm in thickness, but being much flatter and flush.The idea with this coat is to not leave any trowel lines, not even faint ones. To do this you need to come down the wall with the trailing edge of the trowel, this will take some practice to get right. The trailing edge is the opposite edge that you use to run the plaster along the wall. The trick, I have found is to go up against the wall at an angle close to 5° and to come down the wall at an angle around 2° , anywhere 2° or more out is just as good. You may leave some lines as you trowel the wall so you must go over them with tighter angles.
Now is where you come into the final finish, the smoothing out stage. Again, like the wait inbetween the first and second layer you want to wait about 10 minuets or more before continuing. Smoothing out and finishing is just trowlling without any plaster, it simply creates a very very fine finish to the plaster. Flicking water off of your 4″ brush will ready the wall for smoothing out, then dipping the trowel into a bucket of water to trowel and stroke along the wall as in the same manner as in the first and second layer.
And here’s to the end of another Mr Fixing It blog, I hope you learned something useful about skimming and finishing walls and you will come back soon for more DIY tips and guides. From your skimming amigos at Mr Fixing It.