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External render going bad?

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  • 15-07-2023 10:55pm
    #1
    Registered Users Posts: 17


    Hi,

    This new build had its external render put on in July 2022. Just recently (this month) we noticed some web like cracks appearing on the render. It is facing south east direction. It's only on these walls that the issue is visible (so far). Anyone have any suggestion what might be going on and what the best solution might be?




Comments

  • Registered Users Posts: 7,125 ✭✭✭10-10-20


    Opinion here, but I'm interested to note that the render was applied in July. We get breezy and hot days in many parts and I wonder of this dried out the render in patches.

    I do see, for example, what i think are the scaffold levels which the builder worked off (the two or so 12" horizontal lines) and then the splash-back line at the path... so its leading me to think that you're seeing drying cracks and that the lack of a paint finish is showing up the difgering absorbsion and slight cracking from wind-drying on a damp day.

    I don't think there's much more of significance here OP, but perhaps this makes sense to you.



  • Registered Users Posts: 17 playitagainsam


    That makes sense. But I don't think it explains the first picture (with window) which I think looks even worse.



  • Registered Users Posts: 7,125 ✭✭✭10-10-20


    You also have practically zero overhangs as well as zero paint... the window looks worse due to the symmetrical patches which appear under the edges of the cill. Was an unpainted finish specified by the architect and then hence understood by the builder? Are there other houses in the vicinity completed at the same time unlike this one? Sorry if I'm being harsh, but Ireland can be meteorologically unkind to bare-render finishes especially if the curing process was somewhat uncontrolled due to wind, heat or rain.



  • Registered Users Posts: 3,506 ✭✭✭Ginger83


    Not sure what is causing the issue but just wanted to say that must have been a heavy cill. I had a 2.4m window with identical cill. I went with 2 half cills and they were still a struggle.



  • Registered Users Posts: 127 ✭✭FJMC


    Possibly a combination of the mix and not enough control on the drying.

    It might be OK with a painted finish. Possible to test an area?

    F



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  • Registered Users Posts: 379 ✭✭munsterfan2


    We had similar and were advised to paint, used a sealer ( https://proudpaints.com/product/masonry-sealer ) and 2 coats of exterior paint ( https://proudpaints.com/product/30-year-smooth-exterior-masonry?paint_type=exterior ). We painted ourselves last August bank holiday and you could really tell over winter. Here is before & after




  • Registered Users Posts: 7,125 ✭✭✭10-10-20




  • Registered Users Posts: 17 playitagainsam


    There was another house done at the same time, but I don't see any issue with that one. I suppose next step is to confirm there is no hollow sound behind the render and if its OK to put some sealer followed by some exterior paint.



  • Registered Users Posts: 7,125 ✭✭✭10-10-20


    It will look as sharp as a tack as long as it's well primed and painted. I'm not sure about sealing, that's not recommended unless there if a specific reason for it such as previously established water ingress, as it can trap interstitial condensation within the external leaf. Painting will allow that moisture to escape naturally as it's semi-porous.



  • Registered Users Posts: 31,074 ✭✭✭✭Lumen


    It will look as sharp as a tack as long as it's well primed and painted. I'm not sure about sealing, that's not recommended unless there if a specific reason for it such as previously established water ingress, as it can trap interstitial condensation within the external leaf. Painting will allow that moisture to escape naturally as it's semi-porous.

    FWIW the datasheets for the proudpaints products posted earlier are:

    https://proudpaints.com/wp-content/uploads/2022/02/PP-30-Year-Smooth-Masonry-TDS-1.pdf

    https://proudpaints.com/wp-content/uploads/2022/03/PP-Masonry-Sealer-Technical-Data-Sheet.pdf

    You're right about the paint permeability:

    Moisture Vapour Permeability 83.45 g/m2/24 hrs. So (m) = 0.533 (at 146 micron dry film thickness). Test Certificate No.2759* Moisture vapour permeable and suitable for modern Natural Hydraulic Lime Render

    and that sheet also says under Surface Prep

    If the surface is chalky or friable: Apply Proud Paints Masonry Sealer Weatherproof Primer/ Sealer

    ...so whilst the sheet for the "sealer" doesn't mention permeability it sounds like it's more of a primer/stabiliser which won't cause issues. The wall in the OP photo doesn't look "chalky" or "friable" to me but I'm not a painter 😀



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  • Registered Users Posts: 7,125 ✭✭✭10-10-20


    I've seen people apply a silicone based waterproofer as a "sealer", that's what was concerning me. But yes, primer/stabiliser.



  • Registered Users Posts: 738 ✭✭✭gandalfio


    Slightly related, can renders, specifically an acrylic render, be applied in the rain? Or if it needs to be applied dry weather, how many hours without rain does it need to set/not get damaged?



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