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Exterior wall preparation and painting

Discussion in 'Decorating and Painting' started by ColinHardie, 19 Jun 2020.

  1. ColinHardie

    ColinHardie

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    I (like many others during lockdown :)) have been undertaking various DIY projects that otherwise would have probably been left undone for another year. One of these is painting exterior wall(s) of house. The attached pictures show the current state of these....

    wall2.jpg wall1.jpg

    The paint prior to scraping was badly bubbling/flaking and there are a few areas where the render has blown. I am in the process of filling these areas and prepping for painting. The paint that remains is resistant to being scraped off so seems OK to paint over(?)

    Can anyone give me an idea of what I should do to ensure a good paint job that won't just bubble/flake again and need re-done (at least for a few years). My internet searches seem to have conflicting advice in various points i.e
    • Stabilising solution required, yes or no?
    • Mist coat first?
    • What paint to use...any recommendations? Currently thinking Sandtex Plymouth Grey
    • Smooth or textured paint...any thoughts on either?
    Thanks
    Colin
     
  2. ColinHardie

    ColinHardie

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    No advice?
     
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  4. JohnD

    JohnD

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    Is it rendered stonework? Is it in Scotland?
    (edit - yes, I see you are. Rendered stone is not common in my area and I am not familiar with it. The render is probably to hide a defective or unsightly wall).

    I use Dulux masonry paint but no doubt Sandtex is good. Textured is less economical, I find. Standard colours are cheaper than special mix. "This Year's Colours" may be impossible to match in future. Reputable own-brands seem OK but avoid any "basics" or "essentials" value brands as they will be watery.

    The render towards the foot of the wall looks in poor condition, perhaps due to water, either drawn up from the ground or spilling from the roof. You need to rectify that, before patching the defects in the render. Do not use a bituminous or waterproof coating in a doomed attempt to hold back the damp. You can have an unpainted lime-mortar plinth if you want.

    The old render may be lime mortar, in which case use the same. Cement mortar is poor for allowing walls to dry out.

    You need to remove all old paint that is defective or poorly adhering. A scraper and wire brush will do that. Paint that is sound does not need to be removed.

    I like to apply two mist coats, diluted with water, because render is very absorbent. You will probably find the first mist coat disappears into the surface. The second may be enough. You'll know when you have misted enough, because the wall will no longer suck the moisture out of your brush. Because the mist coat will not be seen, you can use up any left-over masonry paint on that.

    if you intend to work off a ladder, don't over-reach, and try not to fall off. A scaffold tower will make the job quicker and easier, as well as safer. Inspect and if necessary repair the gutter while you have it.
     
    Last edited: 9 Jul 2020
  5. ColinHardie

    ColinHardie

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    Thanks for the really detailed response John. Yes it is rendered stonework. My main confusion was around how to treat the exposed render...some saying use stabilising solution, others not. As far as I can gather a few mist coats before painting proper should give a sound base to work with. I have currently filled all crumbling areas, stripped back all loose paint and am feathering in any of the existing paint to try and get as good a finish as I can.
    Again, thanks for your advice and I'll make a point of not falling off the ladder (y)
     
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