Pva?

[ad26]

Help,

I ve plaster two walls this week and had a few problems with them, they seem to have small cracks in places and some bad cracks (only in a small area).

I ve not done any thing different from any of the other walls i ve plaster and they have all came out fine. one wall the plaster didnt take once dried so i chipped it out and there was some small bits of paper still on the wall, so the other walls i really made sure i got all the paper off, but still some what look like cracks once dry?

i ve used a wickes pva should i get a better quality pva?




I done a 3-1 mix on the pva night before and then again and plastered once tacky?

Am i doing the pva to strong? or any idea's on whats going wrong?

Also now the wall has been plastered does it need to be pva'd night before or can i re-skim once tacky today ?

I ve uploaded some pictures so you can see what im trying to explain

 

[trowelmonkey1]

drying out too quickly that is mate, suprised though as you PVA'd the night before, 3-1 is stronger than the 5-1 recommended but it still should have been fine.

i have to say i'm dubious about the quality of wickes OVA for plastering, had trouble with some a while ago, stuck the tub in the bin and only use unibond red now, can't go wrong with that stuff.

in answer to your question , yes you need to PVA the night before again before re-skimming, be generous with it and try it at 5-1.

 

[ad26]

drying out too quickly that is mate, suprised though as you PVA'd the night before, 3-1 is stronger than the 5-1 recommended but it still should have been fine.

i have to say i'm dubious about the quality of wickes OVA for plastering, had trouble with some a while ago, stuck the tub in the bin and only use unibond red now, can't go wrong with that stuff.

in answer to your question , yes you need to PVA the night before again before re-skimming, be generous with it and try it at 5-1.

Thanks TM will give that ago got some new pva today!

 

[NickB_99]

i have to say i'm dubious about the quality of wickes OVA for plastering, had trouble with some a while ago, stuck the tub in the bin and only use unibond red now, can't go wrong with that stuff.

I'm about 3/4 through a 5L tub of Wickes PVA and all has been well so far.

I'm thinking I should probably change to unibond at some point soon, given your advice and that previously on the forum.
Meanwhile to extend the knowledge....
did you have a problem with it from the start or just one time?
In fact does the stuff go off, because it's been in use for about 8 months, at various times.

 

[roy c]

You will be surprised the difference that using different brands of PVA
makes. Use quality brands all the time and you shouldn't go far wrong.
4or5-1 should be sufficient, if you are coating 24 hrs before put it on with a roller, start at the bottom and load your roller so you are pushing the pva up the wall and it is coming off the sides of the roller. when you have done it go back and give it another pass over,when you skim it give it another pass over before you knock your mix up. I would make sure that you are knocking your "muck" up to the right consistencey and once its on don't play around with it. Beginners (I take it you are a beginner,if not I apologise) tend to want to play around with the plaster on the wall I have found this to be one of the main problems lads have when teaching them to skim. Timing is the essence

 

[ad26]

I ve learnt not to play with the plaster too much and gained alot more speed im no longer racing to get the lines out from trying to get it on flat from the start, now i just get it on the wall fast as i can, come back take the line out knock a fresh mix up for second coat. just two walls out of the 11 i ve now plastered have done this.

just pva'd the walls now for a re skim tomorrow so 4-1 pva plaster once tacky ?

 

[roy c]

Yes.
You say you are getting it on "as fast as you can" Why? Get it on the wall its not a matter of getting the lines out. What you are doing is laying the plaster down,(Flattening out getting it ready for the next coat) speed will come as you progress. Also I have had a close look at them cracks, and it looks like they may be on the surface of the wall you skimmed. I would check the walls and see if there are any visible cracks, if so put a bit of fibre-tape over them before you skim them...

 

[ad26]

Yes.
You say you are getting it on "as fast as you can" Why? Get it on the wall its not a matter of getting the lines out. What you are doing is laying the plaster down,(Flattening out getting it ready for the next coat) speed will come as you progress. Also I have had a close look at them cracks, and it looks like they may be on the surface of the wall you skimmed. I would check the walls and see if there are any visible cracks, if so put a bit of fibre-tape over them before you skim them...

i ve only really been taping large cracks do i have to do every hair line crack ?

When i say fast its still most likely slower then most but quick enough to still be able to flatten the wall out i used to spend so much time messing with the first coat that it was nearly set by the time i got back to the start...

 

[roy c]

Any crack that is visible to the eye will open up at sometime or other, as you have now found out .

 

[ad26]

Oh great some of the walls have loads of hair line cracks its gonna take longer to tape then it is to plaster

 

[roy c]

You must be plastering on to old "float and set" plastered walls then mucka is that right? If the walls are "float and set" then the trouble with cracks is usually that the wall has gone "boxy". Give it a tap with your knuckle and see if you get a hollow sound. If the walls are lath and plaster then put your hand on the wall and push gently and see if there is a slight movement. If any of these occur then you are going to get cracks...The only remedy's are taping cracks where there only a few cracks, or more seriously hacking off and start again, or dot and dabbing over the existing ...A crack is a crack and it will turn up like a bad penny (As we used to say)............

 

[ad26]

yeah i think your right (its a 1940-1950's bungalow)

 

[roy c]

Just edited my last post have a look at it....