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Leaking skylight repair advice

mikeysp | Posted in General Questions on


I live in Zone 4a and the pic below shows a skylight on the roof of my neighbor’s house. It leaks when it rains. 

We are trying to buy him some time. 

We used some “through the roof” on flat areas around the skylight, over the tar; however, I think it is leaking through a dry rotted gasket where glass meets metal.

This was tarred over some years back as seen in pic. I thought to put some “through the roof” around the frame and onto the glass and tar along the edge: but, “through the roof” is not good for puddle locations/submersion and that is the reality at the bottom edge of the skylight/glass panel 1/2″ deep puddle which can last for several days at a time in this location.

I had considered a good sealant, but, the ability to adhere to tar, glass, and metal is an important quality it would need.

Thanks for any advice. 


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  1. Expert Member


    I really looks like it is done. I would screw a piece of plywood over the whole thing to limit the damage to the roof until they can afford to have it replaced or removed.

  2. mikeysp | | #2

    Really? Can't it just be resealed with an appropriate sealant?

    1. Expert Member
      MALCOLM TAYLOR | | #3

      Anything is possible.
      Skylights in metal roofs don't typically rely on sealant at all. They sit on a curb that is flashed to the roofing panels, and the glazed portion is factory installed in the frame. It should never need re-sealing.

      Can you just cover everything with more goop and sealants until it stops leaking? My best guess would be maybe.

  3. jberks | | #4

    That is one hell of a skylight!

    I'm with Malcolm, replace it.

    If you're determined, Try tremco dymonic 100 around the glass. Essentially creating a new gasket overtop. Make sure all loose stuff is off and wipe everything down with xylene or another solvent, let it dry, apply Dymonic and tool it in (use painters tape if you want a cleaner look) Dymonic is my fave for most applications, I used it to detail all my siding panels and flat roof penetrations and it's held quite well so far.

  4. mikeysp | | #5

    I wall call Tremco this morning. I had called them yesterday about using Vulkem 116 which I swear by after using it on a tubular skylight several years ago. Straight through a metal roof and 5 years later looked like the day it was installed except for a little algae where the water pools between the ribs and the 21" metal tube. However, the Vulkem 116 was no good for this situation because it is not clean metal, but Tar covered. Since Vulkem 116 and Dymonic are bpth polyurthane advanced, high stretch sealants, I wonderif the same situation exists. Also, I did not ask, but do these high stretch poly sealants work on contact with glass?

  5. mikeysp | | #6

    I called Tremco and they said that the Dymonic 100 and the Vulkem 116 are unsuitable for glass surface sealing. They said the only sealnt would be there silicone based Spec 1. I do not want to even think about silicone in this situation as I have not seen silicone hold up well in the elements, but maybe I am wrong. I think I may apply some through the roof to slow it down this week and tell him all have said new skylight time is here. I called ABC Supply in Nashville and they said new skylight too. I did come across this video about a product called "Turbo Polyseal" but I could find nothing in terms of reviews or contractor discussions about it, so I am a little leary. Looks cool, but where are the users?

    1. Expert Member
      BILL WICHERS | | #7

      Silicone holds up pretty well, but nothing else will stick to it so you might have issues if you have to layer on more sealant down the road.

      Have you thought of just using pitch if this is just a temporary seal? That stuff is pretty gooey and also cheap. Slather it all over the suspected leaky spots until they don’t leak anymore. If it cracks, heat it up and it will reflow and reseal. Sometimes the old school stuff is still a good way to go.


  6. mikeysp | | #8

    OK, just to update. To give him some relief, I cleaned up the surfaces with acetone and a scraper. Then I applied a good coat of "Through the Roof" It is not for puddling areas, however, it does adhere to tar, metal, glass. I spoke with there tech support and they said it would work ok regardless. We went from drip, drip, drip, to dry as dust. This is certainly not a good fix, but it bought him some relief until it is fixed properly. I contacted a couple roofers in the area with good reputations and they will be visiting his house to give quotes in the upcoming weeks.

    Thank you.

  7. tommay | | #9

    If the water is puddling up on the glass because the frame sits higher, you would have to "pitch" the sealant so it meets up to the top of the framing so it can run off.. If the skylight is in its last days and you are looking to buy some time, take a hacksaw blade and make a couple notches in the frame down to the level of the glass for the water to run out and caulk the rest of the bottom accordingly.

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