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Paint bubbling on exterior retaining wall. What can be done?

Discussion in 'Decorating and Painting' started by andyfr, 26 Apr 2019.

  1. andyfr

    andyfr

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    Hi

    We have a blockwork retaining wall which was smooth rendered then left for a year before painting with Sandtex smooth masonry paint. This was done last summer but a few weeks ago I noticed that it is bubbling in places, so I will be removing the bubbling paint before repainting. Is there anything I can do to prevent this happening again?

    Thanks in advance for any advice.
     
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  3. wwwebber

    wwwebber

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    Did you paint it with a watered down coat first ? if not you should. The last time I used exterior paint (Dulux Weathershield) this is what it suggested for new / unpainted surfaces.

    Plus, this should really be in the painting and decorating section.
     
  4. andyfr

    andyfr

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    Thanks for your reply.

    No I didn't water it down. I will try that.

    I wasn't sure if that was just for interior painting. Do you know if it's possible to get a thread moved?
     
  5. andyfr

    andyfr

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    Hi

    We have a blockwork retaining wall which was smooth rendered then left for a year before painting with Sandtex smooth masonry paint. This was done last summer but a few weeks ago I noticed that it is bubbling in places, so I will be removing the bubbling paint before repainting. Is there anything I can do to prevent this happening again?

    Thanks in advance for any advice.
     
  6. JohnD

    JohnD

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    puncture the bubbles. Are they full of water?
     
  7. andyfr

    andyfr

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    No they are just lifting off the wall. Some are bigger than others.
     
  8. 23vc

    23vc

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    Scrape off bubbles, allow to dry properly, repaint bare areas including mist coat (ie watered down). Issue you’ll have is you’ll still see the edges where the paint thickness is different where the patches were. Being render you can’t sand them away.
     
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  10. andyfr

    andyfr

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    Thanks for your reply. I will do that. Would there be any advantage in using PVA diluted to help adhesion?
     
  11. JohnD

    JohnD

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    Absolutely not.

    PVA is water soluble, so when it gets damp or wet, it will turn to slime and fall off.
     
  12. andyfr

    andyfr

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    Okay, thank for that. Really appreciate all the advice. Will be getting the scraper out!

    Cheers
     
  13. andyfr

    andyfr

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    I am reviving my thread as an update to what has happened and hopefully find a resolution to the situation.

    After the helpful advice I scraped off all the loose paint, gave it a good scrub with a hard brush and went over it with a softer brush to remove any dust. I did a mist coat then waited for it to fully dry before going over it with a top coat, this was fine until 2019 winter when it started to bubble again.

    In spring 2020 I scraped off all the bubbled and flaked Sandtex and this time I used a water based white masonry primer & undercoat before two coats of Sandtex. It looked fine for several months until late autumn and winter when it has started to completely flake off. I will try to post some photos to show the extent of the problem.

    I’m not hopeful that anything can be done as it’s obviously the fact that the concrete blocks and render are allowing the water to penetrate the retaining wall and then get behind the paint, but I would be grateful for any suggestions.

    20210110_103245.jpg 20210110_103232.jpg 20210110_103209.jpg
     
  14. freddiemercurystwin

    freddiemercurystwin

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    If the retaining wall has been I'll thought out it will just permanently allow moisture to seep through and will fail with respect to this time and time again.
     
  15. andyfr

    andyfr

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    I thought that may be the case. :(
     
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