Sagging bow window


Old 03-11-05, 08:42 AM
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Sagging bow window

I have a 1960's house with an aluminum bow window. I've been in the house for about 5 years, and about a year ago noticed a significant sag in the window. This fall the sag got so pronounced that I couldn't fit the storm windows into their frames.

The house has about a 2-ft deep soffit, so the bow window doesn't have its own roof, just fits under the soffit. The floor of the bow window is a seat, and has no support on the outside. It seems like it's made of relatively thin plywood (maybe 1/2"?), with a thin bottom frame, maybe 1x2 wood. The frame shows some signs of rot.

I did an internet search and found a few bay window installation instructions that mention cables used for supporting the window by hanging the outside corners to the roof framing.

I looked at the window for anywhere a cable might be attached, and nothing was obvious. I have attic access but looking into the soffit is very hard because the gap between the roof sheathing and the top sill is only a few inches. I probably can't see in there but maybe can feel around. My questions:

Is it likely that my window is supported by cables? Is there any way to tell other than opening the soffit from the outside or feeling around from the inside? If I have cables, should I tighten them, and how? Can I jack up the window and build support under it?

What reasons could there be for the sag, other than a slowly rotting window frame?

I'd really like to avoid the cost of replacing the window if possible. If I replace it, I'll probably have to go with a flat window because of the $$$$.

Any advice would be greatly appreciated
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Old 03-11-05, 10:20 AM
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I have no experience with bow windows that old, and I've never seen an aluminum one. But I have installed many bow windows, all of which had cables which are attached to the rafters. The only other place you might look is on the outside, bottom of the window, directly below each mullion. (the divider between each window). If there are cables, there is usually a large washer and possibly and adjustable nut that can be tightened or loosened, as the need may be. But it's also likely that this may have been covered up by another layer of plywood, soffit, trim, something like that. Unless you've got x-ray vision, you're probably going to have to tear something apart to tell for sure.

The good news is that your bow window can probably be fitted with cables even if your window does not currently have them. I've done this once with great success. It would probably be much cheaper than replacing it, provided you want to keep it for a few more years.
Old 03-11-05, 01:44 PM
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Originally Posted by XSleeper
The good news is that your bow window can probably be fitted with cables even if your window does not currently have them. I've done this once with great success. It would probably be much cheaper than replacing it, provided you want to keep it for a few more years.
Thanks for the quick reply XSleeper!

I think I looked underneath and didn't see a bolt, but I'll check again. Also, the mullions don't look like there's room inside them for a cable, but I guess it could be pretty thin.

Would bracing the window from the bottom be a better bet? I'm wondering whether the window can take that kind of compression (from bracing or a cable). Can you give me more detail about how you added a cable? Did you run it just inside the home parallel to the mullions, or inside the mullions, or some other way?

Thanks again.
Old 03-11-05, 07:31 PM
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When you said your window was aluminum, I guess I was picturing that the mullions between the windows would consist of some sort of hollow extrusion. That's what the cable would run inside.

The soffit around the bow window would have to be removed to do this, of course. For each mullion, you get a length of 3/16" steel cable, a couple oversized 1/4" washers, 4 cable clamps, a heavy turnbuckle (eyelet on one side, hook on the other) and a 1/2 x 2 eyelet with threads, washer & nut.

Drill a horizontal hole through the nearest rafter tail that is above your mullion. If no rafter is nearby, you have to install some heavy blocking between them, and attach it well. Bolt your 1/2 x 2 eyelet above your mullion. Drill a hole up through the bottom of the bow, and into the mullion. (actually this is step one, to see if it is even hollow). Then drill a hole in the top so the cable can pass through. Try not to drill right through the seat of the bow. ha ha! Use a fish tape to fish the cable through the mullion. run the bottom end of the cable through the oversized 1/4" washers. tighten down 2 cable clamps below the washer. (one is sufficient, but 2 are better). Next, turn your turnbuckle so that it's almost fully extended. Run the cable through the bottom eyelet, hook the turnbuckle into the 1/2 x 2 eyelet you installed in the rafters above the mullion and fold the cable down on itself, pulling it down tightly to take up any cable slack and installing 2 cable clamps below the turnbuckle. Now all you have to do is tighten the turnbuckle to compensate for any sag.

On the bow window I did this on, it was *really* sagged. I had to put a bottle jack underneath it to jack it up, and then as I jacked it up, I'd tighten the turnbuckle so that it couldn't come back down.

Perhaps the bottle jack would be a good idea for you to try, before opening anything up and trying this cable idea. Try jacking directly below the mullions and see if you can even move the window. But please be aware that you can't jack too much or you might break glass- especially if the unit has fixed glass (windows that do not open).

Hope some of these ideas help you.
Old 03-11-05, 07:48 PM
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I guess I never commented on your bracing idea. You could certainly do that, but esthetically it would probably not look very good. We've had iron braces (gussets) custom made, to go underneath windows, but the thing is there is no adjustment to them. You would think they would need to be perfect 90 degree angles, but that's not always the case when things have sagged.

You could also jack the window up, as suggested above, and then frame in below it, (shaped like a roof on a normal bow window, but framed in below the window), and then cover that with plywood and your siding of choice.

I guess I don't want to come off as saying the cables are the only option, but they do give you the ability to adjust and "fine tune" the amount of lift you want on the window. Actually, it might not be a bad idea to do a combination of things. I'm sure you'll figure it out.
Old 03-11-05, 11:03 PM
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XSleeper, next time you retro a cable kit, look into buying one from Anderson. The company I get my windows through uses the Anderson cable kit and it works great. I installed a few bays/bows for a company using the turnbuckles and what a PITA, maybe I was so used to using the normal cable kits I'm used to so I'm partial.

When you jack up the window in the front, we always take a section of 2x4 laterally and place it across the width of the window so it distributes the pressure over a broader area. We've installed a few 12' Bows with 36"-you read that right, 36" projection and it worked like a champ.

I would HOPE that since you dont have any knee bracing right now there is a cable kit/turn buckle type hanger system installed. It may depend on how much projection the window has. I've seen many companies/crew not install any bracing at all on bays/bows with 14" or less projection.

If it were me I'd personally disect the top fascia area of the window first that meets the soffit. You may have to remove the soffit first depending on how they finished it off. Once you get the top of teh window opened up you will be able to tell your next course of action. If there is no bracing up top, you will have to move onto plan B and install from scratch. If there is a turnbuckle system you could jack the window and tighten turnbuckle. Have a level on the seat board and tighten it a little past level so when you release the jack underneath it'll go back to a level position with cable stretch. Also before you close anything back up, make sure your operating windows still operate and seal properly, if your rack the window they will not seal/operate as they should.

If it's a cable system, you will now need to disassemble the bottom of the window since the adjustment will be a squedged threaded end on the cable running through the window. Again, jack up window past level and proceed to tighten nuts. Release jack holding window up and check for window operation.

I'm not a fan of any knee bracing, but that's personal preference, just looks soo 70's and nasty. But if this window is in that bad a shape, knee bracing would be the cheapest easiest solution to this problem since it dont sound like this window has many years left in it.
Old 03-14-05, 07:29 AM
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Thanks for all the good advice.

FYI the windows is about 8 ft wide, 16" deep, 5 panel, the outer 2 ones can open (except the left one has always been bound, and the right one is starting to stick)

I tried to feel for the cables thru the attic but no luck - couldn't reach in far enough

There are no nuts or anything on the bottom of the window.

The mullions look too narrow to contain a cable - they look like the frames of each section just butt up against each other, so the only space would be what is left by the change in angle.

All of the above + your comments about having found windows without cables in the past makes me think there are no cables here.

My wife doesn't like the bracing idea either, but maybe I'll try a little gentle jacking, just to see...

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