Skimming etc


Postby Milamber215 » Sat Jun 28, 2008 6:42 pm

hi, have done a 5day courses and purchased a dvd on plastering but they are all telling me different things so maybe you can help me.

1. if skimming over a previous plaster wall how many coats of pva do i use and do i have to wait for it to drybefore applying the skim.

2. do i have to wait for the 1st skim coat to dry before applying the second (final coat) or can i apply it immediately.

3. have practiced a fair bit in my garage, but cannot get the final finish right. For the most part the surface is flat, smooth and glossy but areas appear to have blemishes that i struggle to remove. There is no guidance on the dvd to help me with this problem. The blemish appear as small very shallow shapes (ie as said in previous ) like the various countrys of the world.

My proceedure is as follows

1. pva wall and overskim immediately
2. remove any high points in first skim
3. fill and holes.
4. allow first skim to dry for 20-25mins
5. apply second skim.
6. allow to dry for 20mins.
7. remove high points/ trowel marks using wet trowel and flicking on water
8. paint water to wall, use clean wet trowel to start the smoothing process
9. (at this point my blemishes are appearing) wait 10mins dry trowel 1
10. wait 20mins or so dry trowel 2.

Sorry this long topic but really getting annoyed as cannot see waht im doing wrong.

Darren
Milamber215
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Joined: Sat Jun 28, 2008 6:31 pm

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Postby thedoctor » Sat Jun 28, 2008 7:19 pm

This is the bit that sorts outv tradesmen Miamber. Its why plasterers take about 2 years to get the top finish. Its about timing and "feel". No-one can teach you to get the wall as smooth as a babies bum, it takes practice and more practice. When the top coat is on and it has started to go off and before you start throwing gallons of water at it, is the time to trowel up and keep troweling up until the plaster is pretty well gone,,,,Then its time to flick a bit of water and get the finalpolish but unless the wall is blemish free at this stage this is about as good as it will get. Plastering is a hugely skilful trade. % days will teach you how to get it on the wall, another 360 days will teach you how to get a great finish.
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Postby Milamber215 » Sun Jun 29, 2008 1:11 pm

hi again, thanks for reply, but can u answer the 1st 2 queries i posted for me (don't mean that to appear rude). also what do u mean by trowelling up? dry trowelling? Having, thought lastnite about these marks could they be the plaster drying unevenly?

thanks

darren
Milamber215
Posts: 5
Joined: Sat Jun 28, 2008 6:31 pm


Postby thedoctor » Sun Jun 29, 2008 6:45 pm

If the wall has not been painted 1 coat of PVA mixed 50/50 with water and allow to soak in and dry (30-45 mins) then 1 coat neat PVA which you leave 10 mins to get "tacky" before you plaster. If the wall has been painted then give it a real good scrape to make sure none of the paint is loose or flaky, then paint with 1 coat of PVA 75% - 25% water. Allow to go tack and plaster.

2nd skim coat goes straight on top of first.

Trowelling up is done after you have laid on a coat of skim and got it roughly flat in its original, very wet, state. Its then left for a few mins until it starts to get firm and this is the time you can run the trowel over to take off lumps using the surplus from them to fill the hollows. This is where it gets hard as the plaster is getting firmer all the time but its the only time you can trowel up without leaving trowel marks or the flat spots you have talked about....Yes it can be where the plaster is drying out differently, but this only happens because some parts have been plastered thicker than others. Getting a uniform thickness all over will come with practice.
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Postby Milamber215 » Mon Jun 30, 2008 6:05 pm

many thanks, again sorry if it appeared rude but that wasn't the intention. i get to practice once a wk on an area equivalent 2 plasterboards and just keep re-skimming it. It is getting better its just sometimes 1st coat is drying to quick, even in extreme cases before i get chance to skim the first coat from the bottom up (as i start top left moving to top right then bottom left etc which i assume is correct method) resulting in the plaster being dragged of the bottom of the top half (if that makes sense) when i come up from the bottom left and right.


darren
Milamber215
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Joined: Sat Jun 28, 2008 6:31 pm


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