Doors and Windows - Installing storm door on entryway w/sidelights

Hoping someone who's encountered this can steer me....

The jambs for the entry door are too short due to sidelights, so I would need to extend. The thickness of these jambs is approx. 2", so a 2x4 (or 2x6) added on will not match in thickness - but I imagine I could still do that. And the width of the boards needs to be approx. 4" to go to end of sill/header. So how to attach the extension (2x or other) to the jambs? Can't screw thru 4" of board to tie into jamb. Also I'm concerned about the fact that the glass sidelight is behind this jamb - an error or going to deep might hit/effect glass? I was thinking possibly biscuits. I know these extensions have to be sturdy since all the stress of the storm door operation will bear on them, so I don't want to skimp here.

Thanks for any input...

Over your door, you likely have a brickmould, where the top of the storm door will mount. As you probably have already determined, this is the distance your mullions need to be extended.

If you measure the distance between your mullions, I'm guessing that there is 35" between them? If so, you would want to select a nice 1 1/2" board to use as a "mullion extension" on the left and right that is the full dimension (mullion to brickmould... 4" or so), and install it onto the mullions ensuring the left and right pieces will be 36" apart once installed. (leaving a 1/2" reveal on the interior sides of your existing mullion) This will provide you with the right dimension for a storm door to fit. Then, then just add a full width 1/2" stop on the storm door side that will equal the thickness of your "mullion extension" minus 1" (the width of your brickmould where the storm door mounts). You can cut this 1/2" stop out of some nice clear 1x wood. (You would also need to ensure that the 1/2" stop goes across the head of your door opening, if it does not do that already. I would assume that it does.)

I don't think you need to worry about hitting the glass when you mount the mullion extensions, but I can't be sure since I can't actually see your door from my office. (heh heh) I would attach it directly to the existing mullion with screws, taking care to screw directly in the center of the mullion. If this piece is 1 1/2" thick and 4" deep, you would likely want to use a 5/16" lag that is 4" long, but countersink it 1" deep into the face of the mullion extension. You could also use a Kreg pocket hole jig and attach it with short pocket screws and glue on the operating door side of the mullion extension (the side that will be covered up by your 1/2" stop). I suspect that biscuits and glue would not be a secure way to attach these pieces because you still need to use a mechanical fastener of some sort to hold the piece to keep it secure.

In most cases, I cover these extension with a metal brake and aluminum trim coil, so they don't have to look pretty. In your case, you might need to take extra care to sand the pieces, perhaps priming and painting them before they are installed.

Hope this makes sense.

i use 4" deck screws to attach and also some liquid nails, that eliminates any rocking/movement,especially important with some of the heavy " roll screen " storm doors out there now