Advice Painting Exterior Masonry Window Sills

Discussion in 'Painters' Talk' started by EH11, Jul 31, 2017.

  1. EH11

    EH11 New Member

    Evening All,
    Had some good advice on here previously on a separate project, so thought i'd try my luck again.
    Our external widow sills are pretty scabby looking. The masonry is fine but the paint is warped and blistered. I tried to strip back to bare masonry and realised how long and, in places, near impossible it is to strip back 70 years of paint.
    Using a wire brush and scraper, i've managed to get rid of the flaky paint and what's left seems secure. My problem is, the remaining paint is quite patchy compared to some areas where the paint has been stripped back to masonry. If I paint on it, I reckon I won't get a smooth finish.
    Is there anything I can do to build up the areas that have been stripped back or to apply something thick enough to prevent the rough starting point from showing through?
    Any suggestions / product recommendations / other tips would be appreciated.
    After removing loose paint, I was going to apply a stabilising solution then masonry sill paint - 2 or 3 coats. Will this alone give a decent finish?
    Any help appreciated.
    Cheers
     
  2. Astramax

    Astramax Super Member

    Using a hot air gun often helps shift stubborn paint.
     
  3. Two other options I can think of - one is to use a fine surface filler such as Toupret's products - possibly choosing a 2-part type (mix together and it sets) to fill in all the pits and sections of missing paint. Sand until smooth and level. Then paint.

    The other is to use a high build masonry paint, but they are expensive. Although generally designed to provide a textured finish is used with the correct rollers, I understand they can also be used as a fine filler, perhaps being applied over rough areas using a wide filling blade? But you'd need to check this first.

    If you don't sort the surface first, then it will almost certainly look poor when painted.

    Astra's solution is best, although more work.
     
  4. EH11

    EH11 New Member

    Astramax / DA, thanks for the replies. I tried a heat gun but was a little concerned that I may damage / mark the UPVC double glazing. Ended up using an angle grinder, being careful not to mark the masonry and then wire brushing to get the last of the flaky stuff off. There are large areas where i'm back to bare masonry however in some parts, there remains patches where there is existing paint that seems to be well established. Where there is a significant step, i'll use the tourpets to try and fill / sand back and grade into the masonry to get a smooth finish (this is really DIY hell, but hoping the effort will be worth it).
    Wanted to get your thoughts on next steps. I have bought weathershield clear stabalising primer to apply to the masonry. I noticed the instructions said not to apply it to established surfaces, only to powdery masonry - which the exposed masonry is.
    Does this mean I can't use the primer in the areas where I am priming over the paint patches that appear sound? Seems OTT that I should have to apply the weathershield on the areas stripped back to masonry and another primer / stabaliser for the other areas, Grateful if you could give any guidance?
    Once primed, i'll put a couple of coats of weathershield masonry paint on, anything else i'm missing?
    Again, thanks for any input.
     
  5. Yes, it's hard work - my least fav kind of task. But it should be worth it.

    A number of us are fans of Everbuild's stabilising sol 406 on here, me included. It says "EVERBUILD STABILISING SOLUTION is a specially formulated microscopically fine polymer emulsion which penetrates deeply into dusty/chalky and badly weathered surfaces to leave a stable sound base for subsequent decoration with paint/wallpaper/tiling etc. Suitable for both interior and exterior use over plaster, rendering, pebbledash, stucco, existing painted surfaces, brickwork, blockwork etc."

    This suggests that 406 can be used over existing painted surfaces, which I know I have done in the past and it hasn't caused any issues. However, these products are mainly for stabilising dusty/chalky surfaces, and are not really needed elsewhere.

    NB: I used Wickes' product a number of years ago, again over old paint as well as concrete - that did not work well, and the paint lifted in places afterwards, so I haven't used that product since.

    It sounds as tho' Weathershield's solution is more like Wickes', so I personally would NOT apply it to anything other than bare, porous concrete/mortar/render/stone.

    If you use a small brush - 1/2" or so - you can apply it with enough accuracy. Also, don;t saturate the surface - you don't want it leaving a shiny surface when dry - that's too thick a coat, I understand (certainly true of Wickes' stuff).

    Do a test first - apply a thin coat and see if it's absorbed and how it dries. Then apply the least amount that it'll take to seal the surface, and no more.

    Or else buy 406!

    If the bare concrete is in good, non-porous/dusty order, Astra might even suggest not using it at all?

    Let's see what he says - he's the paining 'pert on here. :)
     
  6. Tishu

    Tishu New Member

    it would be better if you could remove all the paint if possible then make sure it is dry before stabilising then two or three coats of masonry paint should do it.
     
  7. Astramax

    Astramax Super Member

    Ok........strip all paint off, cant see a problem.............fill and smooth off as required.......1 coat of Bullseye 123 let dry, 2 coats of Weathershield Undercoat followed by2 coats of Weathershield Gloss......jobs a goodun, last for years!
     

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