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Double paned custom window install details

Muddytyres | Posted in General Questions on

My contractor has partially installed double paned glass ‘windows’ in our remodel. These windows come as double paned glass, nothing attached to them (no metal no nothing, just double paned glass. Is there a detail on how these type windows are usually installed? I can see the minimal flashing and beads of caulk that are supposed to ‘weatherproof’ these windows and I am VERY skeptical of the install. I don’t know what to call this type of window to look up the installation procedures.


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  1. jberks | | #1

    Hi Sara,

    Can you post a few photos?


  2. Expert Member


    it's unclear from your post whether your contractor is just replacing the insulated glass in your existing windows, or whether they are intending to site build frames for the new glass in the existing openings. If it's the latter, it's a bad way to proceed. Window frames are fairly complex with a number of purposes, including isolating the window from the surrounding framing. Site-build window can work, but are usually not something you want on a remodel.

  3. gusfhb | | #3

    My whole house is this way, all the fixed glass is bonded into frames that are essentially part of the house

    A bead of silicone sufficient to seal a possibly uneven frame. It should be of the type deemed compatible with the IGU[insulated glass unit, the proper name for unframed glass]

    The silicone should ideally be applied on wood surface that touches glass, not where the seal of the IGU is.
    There should be 2 or 3 strips of rubber set on the bottom horizontal surface of the frame so that the IGU is not sitting on the wood, and potentially in a puddle of water.

    Stops get installed on the periphery of the IGU, screwed or nailed to the frame. The only silicone on the outside was a small bead on the bottom stop where the IGU meets the top of the stop, so that water does not run down the pane and behind the stop.

    When I did this I screwed temporary stops to the frame and shimmed them while the silicone set.

    I concur that this is not the way things are done in a 'normal' house, but my house is not normal, maybe yours too

  4. Muddytyres | | #4

    It looks like they’re held in from the outside by the trim, bead of caulk around the glass, there about a 1/2 inch gap between the glass and the sides, bottom and top have short metal flashing but nothing on the sides. The interior isn’t trimmed yet, so it’s held in place by the wood pieces you see in the pic.
    Looks sketchy to me but there are several other much older windows in the house done in a similar fashion.
    They all leak but they’re from early 80’s too.

  5. ohioandy | | #5

    Sara, like Malcolm says, these appear to be "site-built" windows--essentially going homemade with wood where most people are content with prefabricated plastic. These can be done VERY well or VERY poorly. Like everything in a house.

    If you're just now replacing glass from the 80's, and the wood surrounding the windows is generally in good shape, then I'd say the underlying construction and design is good. Rebuilding the windows as they were, only with today's more modern sealants, seems like a sound choice. That's IF you have confidence in your contractor. It sounds like you don't. The details will make or break this installation, and hopefully you can extract some kind of a warranty from your contractor.

    It's hard to judge the details from the photos you gave. You reference some basic flashing--that's good. I can see what appears to be adequate waterproofing on the inside sill--verify that this can drain any stray droplets to the outside. It's not visible in the pics, but the IGU's need to resting not directly on the sill but on small rubbery "setting" blocks, both layers of glass supported. It's also not typical to use caulk for perimeter sealing, which may void the IGU warranty. Better to use a non-curing glazing tape.

  6. mtbphoto | | #6

    Hey Sara, My early 1970's hour has 19 of these double pane glass panels or IGU. They were installed very poorly and the house leaked water and air through the gaps. They put the trim on the outside, then set the window in the opening, then nailed the interior trim to hold the window in place.
    I came in and put backer rod and caulk all around the window to air and water seal. My work should last a few years, but I feel like a true picture window with nailing flange taped properly would be much better.

  7. gusfhb | | #7

    IMHO they are backwards, but maybe they were to begin with
    Any water that penetrates the silicone will end up inside the house

    Mine are the other way round, window installed from the outside

    there is one window installed this way [I think it was a mistake in building the frame] and it will occasionally leak

  8. Muddytyres | | #8

    Update on this- all these windows are going to be removed and replaced with traditional framed Windows. Since installation they have leaked almost every time it rains. My contractor is going to "work with me to make it right".
    The glass/window company that came and set the Windows does not accept any responsibility for the fact that they leak or that there is one that was defective.

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