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New(ish) Sash Windows - Advice on refurb / repair

Hi all. 
I have lots of Sash windows installed about 10 years ago - hardwood frames / sashes with double glazed 4/16/4 units in a 30mm rebate with a 6 x 16mm external bead.  Seems like the design was badly flawed because the sealing between the bead and the glass has failed on most windows, allowing water to sit on the bottom stile causing algae and mold to grow on the glass and soak around the glass onto the inner of the sash and also distort the stile.  What is especially interesting is that there are no spacers between the sash and the glass unit - it sits tight in the rebate on all edges. 
So 1st question - is the lack of a 5mm spacer at the bottom (and gaps at the sides / tops) the root cause of the sealing failing?  If so, I'll need new units (~5mm smaller each edge) and may well have problems with it affecting the sight line (cost and complications).  If not then maybe it's a case of cleaning and drying it all up and rebuilding and resealing.  Any suggestions on how to seal?  What i suspect makes this tricky is that the bead is so small (only 6mm wide) and the front of the house is VERY exposed south facing - so lots of baking sun and rain like its from a fire hose.
Any advice appreciated.
D

Replies

  • DIY_Ex_spurtDIY_Ex_spurt Forumite
    3 Posts
    First Post
    MoneySaving Newbie
    Being a newbie, I’d not realised adding pics was easy. This is external view with 6x16 bead removed. 
  • greenface2greenface2 Forumite
    139 Posts
    100 Posts First Anniversary
    If you have failed units you need to change them . when you do reduce by 10mm and reduce spacer bar down from 16mm and increase the bead thickness . possibly increase the bead shape too . use something to seal the beads in and on . decent silicone or butyl putty the glass should be on packers and treat the rebates if water has been lying on them . wooden sashes are not cheap

  • DIY_Ex_spurtDIY_Ex_spurt Forumite
    3 Posts
    First Post
    MoneySaving Newbie
    Thanks Greenface2 for your reply and helpful comments. 

    The DG units are not currently failed - no condensation in the units -but the foiling along the bottom edge is in a very bad condition.  If the lack of a spacer / gap between glass and frame is not the issue then I'd prefer not to change them just for the sake of it (and cost).  

    Are you suggesting that if I do change the DGUs to reduce the spacer in the units?  So go from 4/16/4?  If so, what would you suggest?  What are the standard sizes?  Doing so would help as I could use a bigger bead, as you suggest - but all this is dependent on a decision to replace the DGUs.

    Is it also possible to reduce the height of the spacer, so it'll fit within the rebate, even with a 5 mm gap at the edge?

    Thanks again!
    D
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