mulling two 3x5 windows

johnny331

I'm looking to mull two 3x5 windows together. I was just looking for some advice. Do I overlap the nail flanges completely, will I need special flashing? How does a mulled install compare to just a single window install?

Sammy

You dont want to overlap... Each window should be installed just like it was a single. Check with the window mfg to see if they have a filler for the mullion area.

AtlanticWBConst.

You should not have to overlap any nailing flanges & you should not need any special flashing.
You essentially install the windows 'next' to each other (usually there is at least two 2x4's placed vertically in between, or stock that will help complete the width of your mullion strips) and then install the trim around the windows to make them look like they are part of one large framed window package arrangement.

You see, a ''mullion'' is a vertical strip of wood (or other trim material), placed between the casements or panes of a window. So, mulling simply means to tie the individual windows together using trim work (this is done on the interior and the exterior sides).

Examples:

Factory fabricated mulled windows (one framed unit):


Example of 3 different windows installed, and then mulled & cased on the work site in order to create ''one large framed 3 window unit''.



Example of 5 windows. Two in the middle were mulled at the factory. Each installed seperately, you can see the nailing fins clearly do not overlap in any way:



Finished product prior to painting (note how this now looks like ''one complete window arrangement''):

__________________
- Build Well -

AtlanticWBConst.

Poor interior shot (low light) of the same arrangement above:



Note: Seperate windows now look like one complete set via mulling....

__________________
- Build Well -

AtlanticWBConst.

FWIW - We usually use 1/4" MDF board for our mullion strips (for painted windows). The strips have to be less than the width of the inside thickness of your casing that you plan on using to install around the window - thus the use of 1/4" stock. We cut and rip the MDF to size and install it like casing (leaving a 1/8" reveal on each side).

__________________
- Build Well -

johnny331

so essentially you just install then side by side, seperated by a few inches, and then the illusion of it being one window is all achieved by wood trim?

AtlanticWBConst.

Yes. The key, as already was mentioned by another poster, is to install them each as an individual window in terms of procedure.
Then tie them together using mullion strips and casing.

__________________
- Build Well -

johnny331

excellent, that clears it all up, thanks!