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Salts from new render ?

Discussion in 'The Pit Stop - General Paint Trade Discussion.' started by Waynetta, Jul 26, 2020.

  1. Waynetta

    Waynetta PPS Master Craftsman PPS Painter Bar Member

    Painted this property 3 summers ago. Two walls were re render due to hairline cracks. Old render still looks great but new parts look like this. customer isn’t happy and asked if I can sort out.
  2. ahenrypd

    ahenrypd PPS Master Craftsman Bar Member

    Not sure on this, but I would have thought you would be good to just repaint.
    Bobbones and Puma like this.
  3. Puma

    Puma PPS Master Craftsman Bar Member

    Looks like the paint might have been over thinned leaving only a little binder in the paint so it has quickly washed away in one area, or the paint was past its sell by date leading to the same effect. Salt bleeding can look similar but is streakier. I would double check the paint in the faded area for strength and sand back if needed. Otherwise I would repaint as normal.
  4. Tomcio

    Tomcio Brush Navigator Bar Member

    It looks like alkali burn I would jet wash (in ideal world all paint should be removed) alkali resistant primer like 123, followed by masonry.
    Sprayandrun likes this.
  5. Wayners

    Wayners Happy to be alive. Bar Member

    Tint coverstain to match (well not that deep but something green) and apply. Give it a weekend to dry...

    Paint over.. Done

    Just unfortunate and it happens and who knows why. Just sort and move on...
    Sprayandrun likes this.
  6. Waynetta

    Waynetta PPS Master Craftsman PPS Painter Bar Member

    New render had a thinned coat of Sandtex smooth masonry (30% water) then two coats un thinned. Paint was mixed for me at crown as not a off the shelf item. New render was a few weeks old weather was great leading up to me coating and sunny weather when applied. Started showing signs of stains within a year But now looking unsightly. Annoyingly for customer the hairline cracks are back too!
  7. Wayners

    Wayners Happy to be alive. Bar Member

    Was metal mesh applied over? Maybe you don't know but cracks should not be back so soon
    Sprayandrun likes this.
  8. Tomcio

    Tomcio Brush Navigator Bar Member

    Curing new cement render take one day for 1mm thickness in perfect conditions. I was using alkali resistant primer if going over new render after less than 3 months of curing never had probs with it other than higher initial cost for the client.
  9. Sprayandrun

    Sprayandrun PPS Master Craftsman Bar Member

    Im going to ask as im from other side of the country is plymouth like how some places in cornwall are where bits of old metal were thrown in when building?
  10. ahenrypd

    ahenrypd PPS Master Craftsman Bar Member

    Oddly BMs metal primer is good for new masonry surfaces. Stops any iron oxide bleed which seems a common sight.

    ( Haven't tried it yet, but Craig mentioned it for a job I have coming up with iron oxide stains. Not sure about alkali resistance).
    mistcoat, Sprayandrun and Waynetta like this.
  11. bobajob

    bobajob PPS Tradesman Bar Member

    One problem I’ve had going over new renders is when the plasterer has put a load of waterproofer in and the paint has a real problem in binding to the surface and it looked a lot like yours
  12. Jason Gunter

    Jason Gunter Sea Fish magnet Bar Member

    @Waynetta ,Is the render cement based(portland ) or a lime based?
    Looked at one similar recently although not as bad has this one i must admit
    Sprayandrun and Bobbones like this.
  13. Bobbones

    Bobbones PPS Master Craftsman Bar Member

    Very good point...
    No two spreaders mix up the same ratio when rendering.. one may larap in a load of plasisiciser..(soz spelling) another a nice limey mix.. So we are asking the old masonry paint to
    Cover a lot of different scenarios.
    ARP to bond and or Bedec to get over the cracks..
    If that render is just hanging there as
    wayners asked about EML screwed into brick work to help with a mechanical key, if that prep stage is missing or a Brittle limeless render was applied then it will crack till the cows come home imo..

    But scratch the above..!looks like two more coats and job doneded...:biggrin:
  14. Waynetta

    Waynetta PPS Master Craftsman PPS Painter Bar Member

    I wasn’t there when render applied so have no idea what went on . thamks guys anyway.
    Jason Gunter and Sprayandrun like this.
  15. crj

    crj PPS Master Craftsman Bar Member

    Just out of interest, has he got the renderer out to look at the hairline cracks do you know?
    Gary scott, ahenrypd and barry like this.
  16. Waynetta

    Waynetta PPS Master Craftsman PPS Painter Bar Member

    On their ‘to do’ List.
  17. Puma

    Puma PPS Master Craftsman Bar Member

    I've been on decorating forums for ages and it is the first time I've head about alkali bleaching. So out of interest I had a look on line and found out that it can happen where moisture gets into cracks. Due to the way it the water dries out the paint around the cracks stays the same colour and the patches in between get bleached. I cannot really tell if that is happening everywhere on the photo but definitely in places. It's a bit clearer with the photo in the link.


    Anyhow I hope that is of some help with the problem.
    mistcoat, Waynetta, Tomcio and 8 others like this.
  18. crj

    crj PPS Master Craftsman Bar Member

    Who's , the renderer's or customers?

    Only ask as it's just as much the renderer's problem as it is yours, if not more so his. Especially if Puma is correct and these cracks are on the new render as you say .
    ahenrypd and barry like this.
  19. barry

    barry PPS Master Craftsman Bar Member

    A great find @Puma .... I’m sure everyone would be better informed by reading your excellent link.
    Jason Gunter, Waynetta, Puma and 2 others like this.
  20. 3 spires

    3 spires I like the no nonsense approach me Bar Member

    To cover your arse @Waynetta email Crown and ask for advise on treatment for this, as if its a reoccurring problem its out of your control just make sure you send the client a copy.

    It goes a long way to show you do everything right I have had a couple of jobs over the years I have been unsure with so I showed the customer what is specified and adhered to, so when it goes Pete Tong the blame isn't aimed at you.

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