They resemble the windows on the front of the house we are building which are separate windows but trimmed inside and out to look like one window. The mull called for on the drwgs is 4 inches. When I was bidding windows, everyone said they would have to be separate windows if I wanted the 4" mull. You could get a single window if you mulled them together but you lose the "big" trim aspect of the window which in our house was crucial to the look we were going for. Hope this helps!

sturdy, do you have a link to your house plan. Thanks for the info!

sturdy, I am trying to decide to mull or not to mull, too. Could you explain this trim consideration a bit more? What sort of look is this good for?

This is the house:

This is the house I am trying to mimic:

Our plans call for 1x8 trim but that is HUGE!!!! We are going with 1x6 on the front of the house and 1x3 on the back and sides for trim.

Here are some pictures zoomed in of the house I am trying to mimic. It is close to my current house and I drive by taking pictures all the time. I keep waiting for the cops to come see me regarding "casing of the joint". LOL!

Beautiful home! I am the same way....I finally knocked on two different doors and they were great to let me in and give me details about what they liked and did not like. The house I am building has an impossible stairway and we are changing that. We are also moving the front door to under the large window like your house plan....all because people were kind enough to give me their time and let me see their homes. I am off to see my contractor with your message. Thanks so much!

The short answer is to trim them in the field.

But it depends on the window you want and how authentic you want to emulate the traditional/historic windows shown in most of your examples.

Typical clad windows that are shipped without trim (nail-fin windows) aren't really "mulled" in the old fashioned way; they are attached either tight together or 1 1/2" apart (for a single stud) and a plastic or metal cap is installed to cover the joint. Unfortunately, the cap doesn't make the joint look like a traditional ganged window assembly. Traditional double-hung windows had weight pockets that forced them to be farther apart than modern windows even when there was no structure between the windows. Even before sash pockets, windows in masonry structures had stucture between them and even Palladio's windows usually had columns between the main window and the flanking windows. You don't need to copy the original design perfectly but when something has become so much a part of architecture for so many centuries you should deviate from it with care and respect. Otherwise, you should design something more original.

To make it look authentic you can either order clad nail-fin windows separately and trim them in the field or you can order wood framed windows (with optional metal clad sash) with any authentic mulled spacing you like and the full trim will be installed in the factory. (Marvin is good at this).

For the clad windows it is important to add a sill nosing (usually PVC-see the ATW link) because so few window manufacturers provide a sill that projects or slopes or is deep enough to look right (or keep water out of the siding below). Adding a sub sill also provides the "sill horns" that extend under the jamb trim in a traditional window.

Some aluminum clad window manufacturers will apply an aluminum trim with the appropriate width between windows at the facotry but they are very expensive.

Here is a link that might be useful: ATW trim

Here are some sites about Palladian windows.

Here is a link that might be useful: Palladian window search

mightyanvil, thanks for the details...great website.