Rendering Staining

Discussion in 'Builders' Talk' started by JohnnyTheKid, Oct 6, 2021.

  1. JohnnyTheKid

    JohnnyTheKid New Member

    Hi

    Hoping I can get some advice on an issue with my new build (purchased 18 months ago) that has been happening for the last 12 months. Every time it rains there is a stain on the rendering below the bay window.

    The developer has said to clean the stain with hot soapy water or micro bacterial wash which I have attempted but with no luck. If it was a stain I would be happy to clean it but its just impossible to remove. Only when the weather is dry the stain seems to fade.

    The window installer reported back to the developer and advised that the window installation isn't considered to be defective and that there is appropriate fall on the cill, which includes a drip detail on the underside.

    Rain seems to be dripping down from the bay window roof in a certain pattern which then falls onto the rendering.

    The developer also suggested that I apply Thompson's water seal to stop the discoloration, but my question would be shouldn't the rendering already have a seal applied that would last a number of years?

    I have never seen this on rendering after rainfall and would appreciate any guidance on how to resolve.

    After rain:

    3.jpg

    Dry weather:

    4.jpg

    Thanks Johnny
     
  2. Jord86

    Jord86 Screwfix Select

    The developer are fobbing you off, open the windows and have a look if there are screws through the bottom of the frame going through into the cill below, do you have a screwgun or hand screwdriver to remove one or two temporarily?
     
    JohnnyTheKid likes this.
  3. JohnnyTheKid

    JohnnyTheKid New Member

    Thanks Jord for the prompt reply, the only windows that open are the side two and I can see two screws in the bottom of the frame, is there something I need to look for in particular?
     
  4. Jord86

    Jord86 Screwfix Select

    I may be wrong but a theory is that the screws are rusting, perhaps due to insufficient drainage holes in the frames, wrong type of screws used, lots of new builds use straps to fix windows in place rather than drill through the uPVC into the blocks but there is no given, nothing would surprise me given the standard of workmanship on the majority of sites today.
     
    JohnnyTheKid likes this.
  5. JohnnyTheKid

    JohnnyTheKid New Member

    Managed to get the screws out of the frame that go into the cill, they are not rusting and look to be correct. Speaking to a window installer chap, he has recommended applying patination oil on the bay roof as he believes the staining is coming from there. Will wait for some rain and see if the staining re-appears.
     
  6. Abrickie

    Abrickie Screwfix Select

    Not convinced patination oil is the answer, untreated lead normally stains white rather than rusty :(
     
    JohnnyTheKid likes this.
  7. JohnnyTheKid

    JohnnyTheKid New Member

    You are right, had some rain last night and the staining has re-appeared :(
     
  8. Tricky Dicky

    Tricky Dicky Screwfix Select

    Just a thought, how has the cill been attached to the wall ? The stains are originating directly below the cill.
     

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