# Window Leak - What is this part of the window called?



## fooyay (Aug 24, 2016)

Hi everyone,

I have an arch window installed directly over two single-hung windows.  I'm not sure if they were installed as a single set originally or not.

We bought the home last March and the arch window had a broken seal, causing condensation inside.  The window was replaced before we moved in contingent to the sale.

A couple months later we had our first heavy wind-driven rains and the windows started leaking from what I can only describe as the "horizontal mullion" but I'm not entirely sure what it's called or the "anatomy" of how it's installed.

I'm not sure if when they replaced the arch window, maybe the screwed up the flashing?  It was a standard replacement -- they popped the old one out, popped a new one in and caulked/sealed.

I've attached a picture of the window, and you can see some of the black gunk/mold that has accumulated there since I caulked it as a temporary fix.

Any information would be helpful.  Thanks!


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## joecaption (Aug 25, 2016)

Post a picture of the outside of the window.


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## fooyay (Aug 25, 2016)

Here it is from the outside.  The water is coming into the interior towards the top right of the window (from the outside), between the arch window and the single hung ones underneath.

I'm not sure about the flashing on the windows, but construction of the exterior is OSB, housewrap and vinyl siding.

Maybe the only way to be sure is to take the siding off.  I can't find any diagrams or information on how windows like this are put together though -- in particular how that "horizontal mullion" is assembled.


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## nealtw (Aug 25, 2016)

It looks like it is 2 windows, with 3" or 4 1/2" between them.
If that is right you will have to pull the top window and install it properly.
Vinyl siding it not water proof so good instillation is a must, this may have been there before the  window was fixed and just made to look good for the sale.
Is there a trim inside and outside between the windows.


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## fooyay (Aug 25, 2016)

From what I can tell, the only thing between the windows (inside and out) is the small divider that appears to be leaking.  I think maybe there is some 1x6 or some similar "scrap" that they're both fastened to.  I'm not really sure on the construction in between the two windows other than that.

I've googled around and can't seem to find much on it.

The windows I've seen installed like this usually are one single window, or they have some space and framing in between them.  But I don't know what the divider is called that the leak is coming from... it feels like it's plastic or vinyl.

Not sure this is something I want to take on myself since storms come and go pretty quickly here, and I don't want to get caught with my pants down (or windows down) trying to fix it on my own.


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## nealtw (Aug 25, 2016)

Whether you do it yourself or have others do it, you want to know everything about window installation so you dictate how it will be done.
So we will educate you on that, but more about your window.
Is the trim on the outside part of the window or something added.
If it is attached to the window is it one piece from the side over the curve or is there a welded joint there.
If it is attached, some of these are made as replacement windows and the trim just covers the siding and would provide a leak almost guaranteed with vinyl siding.
The other type is made with a channel like a built in "J" trim for the siding to go in.


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## Mastercarpenty (Aug 25, 2016)

Likely one single unit. The usual builder's grade method is to fasten the wood frames of the 3 windows together then apply the exterior trim. While they should caulk or glue the wood junctions to seal them they don't. Better grade windows do. 

I'd peel back the siding around the arch and look at how it attaches and seals. If there's no 'soft flashing' there I'd add it. First flash the horizontal tops of the lower windows. Now cut strips about a foot long, and starting at the bottom of the arch go to the top on each side overlapping the strips below about 4" (500mm). one strip at the top a couple inches longer than what it covers below. End of leaks there. If water is still getting in it will be where the arch sill joins the windows below. I can't tell from the pics but there's usually a vinyl "T" molding there or just a flat strip. Caulk the top and sides of that but not the bottom so any water which does find it's way in can drain out. Also check where the pane joins the frame, the replacement glazing may not be sealed in pace properly. 

What I use to caulk things like that is this:
http://www.siroflexinc.com/duo-sil.php
Lowes should have it. It's a paintable urethane/silicone mix which cures quickly and bonds like nothing else yet still has the elasticity you'll need here. Work carefully as it's tacky and smears when 'tooled' with a fingertip so avoid tooling as much as you can. Water clean-up. 

Phil


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## fooyay (Aug 27, 2016)

Awesome info, thank you.

I'm not sure about the exterior trim.  I'm willing to bet it's add-on.  Guess the only option is to take off the siding and see.

I feel like I have a handle on the process.  What I don't have is materials or a truck!  I'm likely going to get a contractor to come out and take a look since they'll have everything on hand.  But at least now I know what to look for when they take everything off and do any repairs.

Thank you again


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