Weak PVA?...hairline eggshell crack fix??

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Ky12

Member
Hi guys, did a job for a mate yesterday and plaster (multi over PVA old wall that had been stripped of paper) started crazed look as it dried. It's only hairline stuff and the plaster so far is sound and sticking.

What's the fix chaps?
Sand?
Reskim?
Filler?
Paint will hide it?

Thanks in advanced
 

choppa

Well-Known Member
Won't be able to put my option in as I can't see how bad it is. Was your pva to weak to start with?
 

plasjack

Active Member
I've recently had this on one of my property's and it was an overskim

The wall might of blown underneath mate
 

choppa

Well-Known Member
I see I had a friend who had the same problem few weeks ago thought it may be you but not haha. I'm from sunny old Surrey :asadito:
 

kgreigh

Well-Known Member
It could be your pva was to strong,on high suction surfaces like old plastered walls you need as @leebo02 said a 5:1 and 3:1 the 5:1 primer soaks into the substrate filling any air pockets,if you go straight in with a 50:50 it sits on the surface and doesn't fill the tiny voids and pockets so when you skim it means the water can be pulled into the substrate through these holes.
 

zombie

Private Member
It could be your pva was to strong,on high suction surfaces like old plastered walls you need as @leebo02 said a 5:1 and 3:1 the 5:1 primer soaks into the substrate filling any air pockets,if you go straight in with a 50:50 it sits on the surface and doesn't fill the tiny voids and pockets so when you skim it means the water can be pulled into the substrate through these holes.[/QUOTE

what a load of tosh!!!
 

kgreigh

Well-Known Member
Care to explain your theory,i don't claim to know everything and I'm always open to learning something new,especially if I have said or doing something wrong.

I have had it happen to me before on old s&c and lime when using 50:50(2 coats),the couple of times it happened was on different jobs and the skim pulled in quick like there was to much suction,i was chasing it and the next day it crazed all over.both times in the same set I skimmed different surfaces ie board,hardwall and paint so ruled out any rapid drying due to heat or dodgy finish etc,the only theory that I believe can explain the crazing was what I explained above.
 

S a plastering

Private Member
Was the old plaster well stuck to the wall if not this will cause cracking dosent matter how many coats of Pva you give it the substrate will still move
 

Ky12

Member
Great replies thanks guys.

I changed brand of PVA and let it almost dry and hit the other walls well today with no problems.
I reckon my crazing was too weak + poor quality PVA, combined with super hot room. I learnt today he had been steaming paper from the walls half hour before so they might have something to do with it.

Out of interest, should it happen again.... What do you do to fix it once it's dry? Assuming it's adhered sound
 

Ky12

Member
When do you go on with your second PVA coat when throwing on a pissy mix? When the first has fully dried?
 
Great replies thanks guys.

I changed brand of PVA and let it almost dry and hit the other walls well today with no problems.
I reckon my crazing was too weak + poor quality PVA, combined with super hot room. I learnt today he had been steaming paper from the walls half hour before so they might have something to do with it.

Out of interest, should it happen again.... What do you do to fix it once it's dry? Assuming it's adhered sound


Could it be the paste still on the wall?
this happens with paint too if put on the wall with paste still on.
 

leebo02

Well-Known Member
Oh

Oh ok...that's not to bad just a ball ache on time. Was dreading you saying it's got to be fetched off.
Could you just redo the affected areas patch repair style?
its just as quick to uni bond the wall again ( at least 2 coats ) and reskim, no need to take plaster off if its adhered well, you could try easifilling the crazed areas but probably just as quick and a better job to redo wall
 

leebo02

Well-Known Member
When do you go on with your second PVA coat when throwing on a pissy mix? When the first has fully dried?
the first coat of pva needs to be fully dry before you apply second coat . i like to give it the first coat the day before,
 

Ky12

Member
Cheers for the knowledge dude.

Some say just one coat of quite strong, some say 2 coats always, some say the second PVA coat loosens and reactivates the first?? Any rules of thumb here to go by?

Quite a science to a tub of glue haha
 

Ky12

Member
Could it be the paste still on the wall?
this happens with paint too if put on the wall with paste still on.
Could well be that too....I sprayed a little water on the raw wall (without putting anything on) and rubbing my hand over it, felt kinda gloopy. The 2 coat PVA stop this too or there a smarter way?
 
Could well be that too....I sprayed a little water on the raw wall (without putting anything on) and rubbing my hand over it, felt kinda gloopy. The 2 coat PVA stop this too or there a smarter way?
Spray with water and scrape off.
Wash wall with sugar soap when you've done that.
then pva and skim
 

jamesthefirst

Private Member
I had a similar issue recently on a very high suction wall, i used weak pva as i had run out of microgobetis/betakontakt. Same as you it crazed but was solid.
I put on another pissy pva when the crazed wall was fully dry and 2-3 hours later put on a slightly watered down micro. Trowelled in a treat.
 
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