Technically you could probably just mull them all together but it would require a header above them which could span 20 ft. which may not be practical.

Could be other issues though and it would be better not to just 'guess' without knowing the exact details.

The minimum practical amount of wood between windows is probably 3"

Thanks Chris!

So three inches as in I 2x4? Or what size wood?

a 2-2x4's would produce an actual 3" x 3.5" or if your walls are 2x6 they would be 3" x 5.5"

But be careful -to do this requires your header to run the entire span. And there are other possible problems for bracing requirements. Your builder should be advising you.

This is a question about structural design rather than framing technique. The wall might be supporting a second floor and/or roof and it might need to provide lateral resistance so it must be designed by an engineer rather than by you or a builder.

You have not even brought wind loads into play, more info is needed and this will need to be figured out by a professional as there are allot of things that have to be considered.

This post was edited by millworkman on Wed, Nov 6, 13 at 8:47

Talk to an inspector to find out how many windows in a row are allowed on one wall. This might save allot of headaches and money down the road.

We have the same scenario in our home were building now. We have 4-28" windows in kitchen (total of 9') were getting them as one unit mulled in between. If you decide to break them up remember to factor in how your molding will look both inside and out.

Would love to know who makes the 48" x 90" windows, aktillery. Aesthetically, I think aluminum fixed windows look much better when they are trimmed out individually rather than factory mulled. We had both in a former house. While you may give up an inch or 2, it just gives a much more finished look. I'll try to post a photo.