Mitered Windows

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Mitered Windows

Post by Thewes »

Does anyone have any information on where to purchase mitered corner windows? All of the architects I previously worked for would build their own, but those projects were always high budget and in most cases, were being built in house.
Is there a lower budget alternative that anyone uses?
Thank you for your help.

outside in
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Post by outside in »

Both Marvin and Pella manufactured corner windows - Marvin was first, I think, and used bent glass at the corner to create a tight seal and prevent the insulating gas from escaping - then Pella came out with a mitered corner a few months later. I believe both have now dropped the glass from their product line. They were extremely expensive, had limited sizes, and one ended up designing the house around the sizes they made (if the client could afford them) - so I think you're stuck with a custom-made window. You could call Pella or Marvin directly, I'm sure they would make them if you paid them enough - but a local millwork shop could probably make them for less money.

Paul Ringstrom
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Post by Paul Ringstrom »

I saw an interesting solution to the pillar-less corner window by John Randall McDonald. He used two pieces of acrylic about 3/4" thick and joined them with clear silicone sealant. Another alternative would be to use polycarbonate.

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Post by pharding »

In my opinion the term mitered glass corners is a misnomer. I believe that the term butt glazed is a more appropriate term. The butt glazed corner windows in FLW Usonian Houses were done with single glazing. Insulating glass was available starting about 1945. FLW did not like it for whatever reason. If a client requested it, FLW would talk them out of it. With insulating glazing the butt glass corners take on a different, slightly heavier appearance. Obviously insulating glazing is desirable from an energy conservation perspective. The look of butt glazed insulating glass corners is not offensive in my opinion, if it is detailed properly. However it is more expensive than single glazing. For some projects a hybrid approach may merit consideration with insulating glass throughout except on the corners, which would be single glazed.
Paul Harding FAIA Restoration Architect for FLW's 1901 E. Arthur Davenport House, 1941 Lloyd Lewis House, 1952 Glore House | | LinkedIn

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Mitered glass windows

Post by dkottum »

FLLW often created his own vocabulary to describe his innovations, and he liked to be somewhat poetic. I can understand why he would not choose to call his corner windows butt glazed. Mitered glass seems to be an accurate description as the glass was to be ground to a mitered corner. I recall one story where glazers said they could not miter the glass. He asked them if they ever tried it, and they said no. He challenged them to try it, they did, and the client had mitered glass windows.

We have used this in our own house, but I could not find anyone who would attempt mitered glass. So we butted the corners and sealed them with silicone. They look perfect from the inside, but on the outside you can see the edge of the overlapping glass panel. Okay, but not elegant. They are also not as strong a joint as mitered glass, because a really strong wind could bow one side of a long butted corner, but not a mitered corner.

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Post by peterm »

We have a true mitered glass corner in our bathroom addition here in Altadena. The framing had to be extremely square and exact, and the glass was cut at a true 45 degree angle. The result is that when looked at from the right vantage point, the corner virtually disappears and there is only a hint of a crisp line. I'll try to take a photo and send it along.

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Post by ozwrightfan »

I would think that the outside edge of the mitre would be like a knife edge and thus be quite vunerable to chipping.

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Post by Thewes »

Thank you very much for the replies.
What Mr. Harding suggests is exactly what we did on previous projects in the offices I worked - both in the cold weather of Chicago and in the mild weather of Albuquerque. Double glazed on all of the windows except the corners, where we used single pane and siliconed it together.

I would love to see some pictures of your addition peterm, but I was thinking just like ozwrightfan... doesn't that create a razor sharp edge on the outside?

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Post by DRN »

The glass does get razor thin at the outer edge and can be chipped. If it is not chipped, there is no discernable edge to the sheets as they have a clean tight fit, though I wouldn't press my finger to it and slide either. The dining area at the Sweeton house does have a small chip; the other original windows have not chipped in the 58 years they have been in place. As a precaution, I mow the grass myself and always in a pattern that directs clippings away from the house.
At the main entry, there is a full height reverse corner of mitered glass (directed into the house) which I was told was broken in the 1970's. The replacement glass was mitered, but also rounded slightly to prevent a razor edge indoors. From the corner's inside view (in this case from the exterior porch) there is a slightly more pronounced line at the joint, but not detrimental. A more noticable issue at this location is shifting of the glass in the sash ( about 1/8") due to slow deterioration (cell membrane compression, bugs, some rot) of the sash itself. Painted pine was used by Taliesin for the sashes at Sweeton in an effort to control costs... the result is greater vulnerability to deterioration of the sashes than some of the other houses.
Of note: in Wright's time, the full height glass and glass in doors was not tempered. If these pieces are to be replaced today, the glass must be cut and mitered prior to the heat treating. Mitering already tempered glass will break the glass unit.

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Post by JimM »

Mr. Hardings approach worked perfectly for us. The windows are insulated except at four corner areas that are 1/4" glass butt glazed with silicone sealant.

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Post by peterm »

Here are photos of the mitered window in our bathroom addition: ... 951729599/

Upon closer inspection I realized that what the builder did was to cut the two pieces of glass at a slightly larger angle than 45 degrees making the outside opening a tiny bit larger allowing a bead of caulk to be inserted. The contractor wanted to "butt joint" the glass, but the architect and myself persuaded him to give it a try. He was relieved that it worked.

Also note how the glass was notched around the ceiling joist...

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Post by flwright »

Here is a detail I have referred to on a few occasions on this forum that adds a second layer of glass to the mitered glass window and provides marginally better thermal performance. ... 278948450/

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Post by Wrighter »

Here's an option, from Taliesin, that no one has mentioned yet. It solves the difficulty of the mitering, but not, I'm afraid, the energy efficiency issues. ... 4787615010

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Post by peterm »

My favorite, especially in February...

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Corner windows

Post by Healeyjet »

I just found some corner windows by a manufacturer that I am not sure people have seen.
Ward ... orner.html

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