Plastering a wall to perfecton

Posted at 10:47

So at long last, I have finally got around to doing some of the promised plastering. And in order to do this, it meant that the wallpapers and dado rails would have to be stripped off first and unlike many road recovering processes, any prior alterations to the walls like moving electrics, adding extra sockets and the like would be done first, leaving us with perfect un-patched walls in the long term.

But for now, let’s go back to the stripping for a moment. There’s not much to be said here, I know it’s a pain in the ass job but it has to be done otherwise any wet plaster added above it would simply blister and ruin the whole point.

There’s no real method to stripping walls and many of the so called trade secrets I have come across in my time have proved to be less than effective. All I can suggest is hard labour and a patient and methodical approach to it. Oh, and a steam stripper is a big help too.

Once the walls are stripped, leave them to dry off and then, for best results, give the walls a quick light sanding. This is to rid the walls of those tiny little blobs of paper often left behind, which cause bumps under fresh papers or can lead to serious drag marks when plastering.

That done, now is the time to consider the changes you wish to make if any. In the case of the wall I have chosen to showcase, I had to move the light switch which was now concealed by the re-hung door. That would mean chasing the wall to reposition the cables feeding the light switch and removing the switch and back box. While at it, the whole affair was properly fixed to the correct wall.

So, are we finally ready to plaster? Well not quite...

Only a couple of things left to do now and they are to first backfill the chases we created for the electrics and any other holes in the wall. We do this because it means that the substrate of the wall is more or less level and ready for a top skim coat.

Without going too deep into the whys and wherefores of home electrics, I will state two things here. First off, it is a trade standard that all cable runs should be made either vertically or horizontally across walls. The reasoning behind this is to make it easier to trace cables avoiding the inevitability of nailing into them when hanging pictures etc.

Secondly, I’m going to mention cable capping. Contrary to popular belief, these are not for cable protection or even to provide a means of trunking for later cable additions or removal. Believe it or not, they are only there to aid the plasterer when base coating. They simply hold the cables together and prevent them from being dragged across the wall while the plasterer spreads. Needless to say, with a clean cut chase and only minor back filling required, these cappings will not be used here.

Re-positioning of the light switch. Note the vertical cable run.

And now finally, we give the wall a coating of PVA (poly-vinyl acetate) adhesive. This will help seal in the old plaster substrate, kill the suction of the wall (which would lead to too quick a drying time and subsequent cracking) and help key in the skim coat.

Now we are all set to go... Let’s start mixing.

For our backfilling exercise, because we didn’t need the additional cost of a whole bag of base-coat plaster we will use the same skim coat plaster, but it will be a stiff mix which will harden faster. This will be mixed to the consistency of hard butter and simply pressed into the chases and other holes. If it is too hard to work with, you can always let it down by adding a little more water. The stiffer a mix it is, the faster you can move on though.

And for the major skimming task, we start with a clean bucket filled with one third capacity of cold water. Generally speaking, all plasters will take one third water to give just under a full bucket of mixed plaster.

To mix the plaster you can use either a stick or a paddle in an electric drill. With the stick method, you simply sprinkle the plaster into the bucket while constantly stirring. We are aiming for a consistency of an easily spreadable margarine without any lumps so the stirring can become quite a vigorous task. Meanwhile with a mechanical paddle, the plaster can be added en-masse and the paddle will do all the work for you.

Try to get the right consistency. Too hard, and the plaster will set too quickly and be harder to spread. Too soft, and it will simply pour or drop of your trowel and hand-board. Only experience will tell you what quantity of plaster you will need but a general rule of thumb for skimming plaster is one bucket for an average 12 foot wall.

Now we are set to go...

It is worth mentioning here that it makes sense that when plastering two adjacent walls, it is better to let the first one set before you begin on the second, although when you become more accomplished and confident, it is possible to do them concurrently.

So... that’s one wall down, and only another 19 to go for this place.

Plastering a wall to perfecton

   

2 Comments:

1. stephie said...
   21 February 2011 at 10:59  
   only another 19 to go lol! I better come over and help then! any other volunteers?
   dokan sam said...
   17 April 2013 at 14:20  
   h as forming a layer of plaster on an interior wall or plaster decorative moldings on ceilings or walls. Very impressive post! I love these updates! Thanks for sharing wonderful info!
   Plasterers Merseyside

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