Anyone have any tips for skimming onto old plaster? Managed an almost perfect skim onto plasterboard but finding that old walls are much more difficult. Any slight lumps and bumps mean that the you are more likely to miss bits when trying to get a good finish.
I primed the surface first with PVA which I think helped to increase the working time. Total thickness of the skim was about 2-3mm. Can you go thicker than this on old walls to help cover up any imperfections ? Applied in two coats, the second applied just as the first was begining to set.
Also found that there were a few grit marks. Badly mixed plaster ?
When ironing out the trowel marks as the plaster is setting does anyone have any tips on which way to work across the wall. Should you go top to bottom or left to right? Are long sweeps, short sweeps better ?
Done this also, but waited for the first coat of plaster to dry out. Not always possible but it stops the second skim coat being "pushed" into the first skim, if that makes sense.
Maybe a dirty bucket containing left-overs from a previous mix? It pays to keep *all* equipment including buckets / mixing paddles spotless. I used to use a piece of 2x2 but invested in a paddle to mix the wet stuff as its easier to keep clean.
Whatever is the comfiest. I find that at first the sweeps are longer with greater pressure, gradually diminishing as the bumps and curves get flatter.
HOT TIP: Stellas Law :- I *NEVER* skim without at least 1 can down my neck, then I got something to blame when SWMBO spots a flaw ;))
============================================= There's no golden rule to Plastering if you feel comfy the way You apply it then settle for that. One tip I can give instead of having a large pasting brush in hand to dampen plaster as your Polishing it, use a spray bottle.
Thanks for these tips. Another question though. If you are skimming a largish wall e.g. a hallway or stairs is it possible to split the job into two sections ? Skim dries out quite quickly and I don't think I could get a 4m wall done in time. Is there a standard technique to get a good join between the two or is it time to call in a pro who can work at a decent speed ?
It is a bit tricky to skim a large wall. Make a slightly sloppier mix to give yourself a bit more time. If you start at one end & as you work across, you'll find you're skimming one area whilst polishing another. You'll need someone to mix as you will be quite busy working the plaster. Give it a try. If it ends up a mess, you can always get a plasterer in to skim over it. As Grouch said, use a spray bottle. The 1 ltr garden sprays are ideal.
================================================= Get your Missus to do the mixing. :o( this will give you an edge over covering the wall in one fell swoop, make sure the Mix is sloppy try to get in the knack of sweeping the Plaster in large sweeps, either up the wall or across. I'm no Master plasterer and have to Mix the stuff & apply it. Two of my walls are ten foot high by twelve feet across when I first started I thought Jesus! I'll have to work lig a pig but when I actually got into the swing of it they where both done in no time. pant! :o) I'm only 5 foot 2 inchs/9 stone. But got the stamina to tackle and finish.
Yes. Pick a join line, plaster slightly over it, and before the plaster has gone fully off, cut back the edge to a clean step, and not feathered, as you can't feather in a join. If you know where the join is, you will always be able to see it on the finished work, but a good join won't notice unless you look for it. On many houses, you will spot a join on the wall where the staircase is, as the plasterer probably didn't do it in one go.
Hum -- skim normally takes a day to dry out IME, much longer than it takes to go off (set).
Remove any obvious lumps above the surface. The first skim coat goes on normally as thin as you can but should leave the plaster level with the most proud bumps remaining on the wall. i.e. you tend to scrape the trowl edge over the rough surface, but it should leave you with a flat surface. The reason for the second coat is that you can't polish this first coat because of the background coming to the surface in places. So the second coat is then put on ~2mm thick to give you clearance over the most proud bumps on the background, and that's enough to enable you to polish the surface.
Yes. The issue is that plaster finish coat shrinks when it sets. A thin coat shrinks by getting slightly thinner which doesn't notice, but a thick coat may crack.
Possibly. Check you aren't leaving unmixed plaster up the sides of the bucket, only to fall in when you pour the plaster out. Other sources of grit are from the wall (PVA should have stopped that) or from adjacent walls/ceilings. I had fun plastering a wall up to a ceiling artexed with small stalactites. The trowl edge would keep breaking them off and dragging them into my plasterwork ;-)
Generally inwards from all the edges. Keeping the edge of the trowl parallel to the wall edge, start the sweep along the edge but in a circular motion which sweeps out and ends a quarter turn later in a direction perpendicular to the edge, but without turning the trowl. When you aren't near an edge, it doesn't matter.
Thanks for the tips. Do you complete the whole wall with the first coat following this method and then the second coat or are you applying the second coat on the earlier sections as they begin to set as you work along the wall ?
Put another way - do you have to follow the second coat quickly after the first as you are moving along the wall or can you complete the whole wall 1st coat and then go back and do the 2nd coat.
Thanks for these tips. One thing I have noticed is that you polish up the plaster and think you've done a great job. However, when the plaster dries out and goes a lighter colour you see small areas (no bigger than 10 pence piece in the worst places max) where it looks like the plaster has not been polished up properly. I have seen this to a lesser extent in pro's work too and can't figure how why this happens.
This never happens to me on plaster board so I can only guess that maybe the wall I am going over is not perfectly flat. As you polish up with the float you are missing tiny dimples in the wall as the float is passing over them. Anyone else come across this ? Anyone got a fix?
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