Since the windows are side-by-side, treat this as one shade, not two. When I do outside mounts, I tend to line up the shades with the far edge of the window casing on either side, and from the top of the casing above the windows. Alternatively, you could mount the shade from the ceiling.

Floral Linen Kitchen Valance · More Info

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Note the really simple valance at the top of the window treatment in the second photo. A good way to hide the mounting hardware.

Thank you, Sabrina! When you say "treat it as," are you suggesting just buying one wider shade to cover the whole window? And, if not mounting on the ceiling, you would not mount a few inches higher than the window casing? I guess I'd always heard that was a way to add height and avoid blocking light when the shades were raised.

Yes, one shade for the full width of the two windows together.

Okay, that's something we'll definitely consider. I'm still curious about the height. I found this example going all the way up to the ceiling. I like it in this photo, but our ceilings are low and our rooms are not necessarily large or grand. Would going to the ceiling look proportionately weird since our windows don't go as close to the floor, either?

In this photo they don't go all the way up.

I would do 2” above the window, 1” wider each side, and two shades on one headrail.

I agree with Sabrina! It will look at lot better with the one continuous piece across the top. If you really want the function of the two shades tho you could do a split headrail (1 headrail with 2 operable shades within it) and have the valance go all the way across. For outside mount it is always ideal to have it end at the edge of the trim. Otherwise it could look out of proportion and not very custom finished.

You need them slightly wider at each end for overlap. You could do 1/2" each side if you're concerned. It will not look out of proportion. It's really not that much that anyone would notice. I used to make custom, so they will look custom.

I would do one blind with a wrap at the end of the top valance to cover the mounting hardware. Just think...can you ever imagine yourself ever lowering just one side of the blind or the other? Probably not.

Thank you so much! I think we will go with one long shade instead of two, per your suggestions. As I'm looking at options, I also can choose to have a valence or no valence (some lift options don't require the valence). Any opinions there? I guess I feel like the valence makes it feel a little formal (I don't want too formal), but I don't know if it would feel too plain without.

If you're having fabric shades made, a flap out of the fabric, can be made and attached at each end to hide the hardware, so you won't need a valance.

I would be concerned about the weight of a single Roman across a double window. Those get heavy really fast and wear out the hardware as well as your arm. While I love the look of a single shade across the double window, I think you d be happier with 2 shades on one head rail.

Thanks, blubird! I was concerned about that, too. However, I'm seeing an almost $200 price difference between just one long shade (less expensive) vs two on one rail. :-/ Unfortunately, we moved into a house with zero window coverings, and it's adding up fast. So the price may hold weight, here!

I realize I am late to this post, but I have a very similar situation in a bedroom where I need to outside mount. I'm trying to decide between one roman shade over both windows or two separate shades on one headrail. My problem is that the fabric will have to be seemed in two places, if I chose one shade. Won't that look strange? Help please.