Lime wash, not enough PVA or both?

[mrjoe]

Hi all,

I'm a beginner at this plastering game. Having been on a 4 day course I set out plastering our newly knocked through kitchen dinner, after a few relative successes I've hit my first major hurdle.

Having finally plucked up the balls to tackle the biggest wall, I was pleasantly surprised at how easy it went on. Happy with my work I sat back and revealed in my glory. By 9pm ish I thought I'd go and give it one last polish and was horrified to notice a 1' x 2' section was pushing away from the wall, flexing as I pushed it. With very little persuasion this cracked and started falling off. Thoroughly demoralised I opened a beer (alcohol free, dry January, insult to injury).

This morning I scraped the rest off, well, what wants to come off. As you'll see from the picks, above the old picture rail seems fairly solid on and underneath the RSJ was back to bricks then a bonding coat so this is solid too. To the right of the RSJ was a different wall surface this also seems good. Bits of the wall that now has no plaster didn't come off easily at all and other bits just fell off.

I did two coats of PVA 1-4 but having mixed plaster and started I did notice it was pretty much dry and not tacky. In hind sight, I should have stopped then.

Having done a bit of reading, I'm wondering if what I thought was paint is actually lime wash, any thoughts? How do you identify lime wash?

Planning my next line of attack and wondered if anyone has any advise.

I thinking maybe a stranger mix of PVA and make sure its still tacky when I hit it or - less preferable but possibly safer - somehow get all the paint/lime wash off first. What do you think?

Thanks in advance,

Joe

 

[mrjoe]

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[Micilin]

On the flakes of your plaster that came off, is the lime wash stuck to them?

I am asking if

1- Your plaster stuck to the lime wash and the lime wash came away from the wall or

2- Your plaster did not stick to the lime wash, which is still sound on the wall

Regardless always make sure sibstrate is sound and PVA tacky. If you did not seal up the wall the day before, then PVA is not much good on a high suction background. Was there any crazing/turtling on the plastering during or after completion?

 

[mrjoe]

Hi Micilin,

The back of the flakes were slightly discolours like some of it may have come of with it and if you look at the first photo, the left wall is what it all looked like before and the right wall is after so some of it has clearly come off.

Just google imaged plaster crazing and don't think there was any of this going on. Had the bi-fold door open all day and only about 10deg in there.

Are you saying PVA the day before?

Think I need to get out the sugar soap and a scrubber.

 

[Micilin]

Yes, if using pva, do it the day before then again just before plastering. always plaster on to tacky PVA.

Bondit or WBA are better IMO and easier for the novice.

Sounds like you just need to get any loose stuff off before plastering. The moisture from the plaster may have softened the substrate , helping it to come away. Bondit (or SBR) the day before would have eliminated this problem but still one should always make sure the backgroound it sound.

 

[mrjoe]

Thanks for that,

I've started having a go at scraping it off, softened up a bit when I wet it down but still pretty slow going.

Your saying I don't need to get it all off though? Just what comes off easily then PVA the day before (Bondit or WBA), then again before starting and make sure its tacky.

I was using B&Q cheap PVA before, think I'll upgrade. Is 1 to 4 ratio OK?

Thanks

Joe

 

[mrjoe]

Bit of a side note,

I always believe in using the right tool for the job but having sharpened up my bucket trowel with a finishing file it works way better than any scraper I've got