Side-by-Side Double-Hung windows FAQ

Either way is fine. Wherever you order windows you should be able to order them ganged up as a single unit if you want that. Assuming you have a sufficient header, that way would be a little less work.

It somewhat depends an how much space you want between the two windows to g et them to fit easily in the available space witha new header and wall stud s. If you want them close/touching, then you need to figure out what the fa ctory will do for a double vs what you could do with a 1x4 (maybe) between the two windows.

Well, having worked for 2 different window companies over the years, I can say both ways are valid - but you get a better looking installation if you order the pair with the joining moldings included, assembled and sized to fit your rough opening. Makes a neater intall both inside and out, as long as your header is adequate for the span. If the header is questionable, putting a post in between gives you a stronger structure. In your case the header is LIKELY strong enough, unless it was depending on the door framing between the door and sidelight for support (which SHOULD not be the case, but you never know without actually seeing the installation up close.

If I were doing it, I'd order the custom unit for sure.

Absolutely the best way to go.

I don't see why it has to be a custom unit. Just frame it out to the size of a double window that's available.

Thanks everyone for the replies and suggestions. It seems like we could do it either way, but several people suggested that option "1" may be better for aesthetic reasons, ease of installation, etc. We'll check out the support issue, but it probably won't be a problem since there is a lintel in place already across the top of the entire opening, plus we can add the right type of header if needed.

We do want to go with standard size windows, not custom sizes, since we will be framing the opening anyway. So, one advantage to just buying two off-the-shelf standard size windows at Lowes or Home Depot etc. is that we can get them right away without waiting for a special order. We will check just in case to see if Lowes or HD stocks pre-made side-by-side double hungs that would work. We will probably want to do this job this coming week, but I'll also check with a window supplier to see what they have and if they can supply them in a short time frame.

In doing research, I found the term "mullion" or "mullion window" to describe these. The online research also talks some about deciding how to do both the interior and exterior trim, and those issues may point us toward buying them pre-made rather than putting two single windows side-by-side and then doing the trim (inside and outside).

I also found this YouTube video which shows one Bob Vila approach: