Changing a door to a window

I know this sounds idiotic but the previous owners of our home are the real dum dums. On the 2nd floor we have an east bedroom that for some reason had a door put in it so you can go out onto a rickety deck (and peer straight down into 4 neighbors' yards). The room has literally hit 90 deg. already (not all the doors fault but it's not helping). My dh wants to get a new door even though we'll be taking down the unused deck at some point because he thinks the cost of turning the door back into a window will be too high. Anybody have an idea how expensive that could be? We have vinyl siding on the outside and the window would be about 3'X4'. The door will be a temp fix.

 

Retrofitting a window into a door space is alot easier than the opposite, and since you have the materials to match the outside, you are already halfway there. Once you remove the door, you will need to determine the height of the window header in order for it to match similarly to nearby windows. You don't want one window sticking 6" higher than an adjacent one. So build down the header if necessary, determine the rough opening for the window and build a cripple wall at the bottom, fill in the side to fit the window RO, and have materials on hand to build out the exterior portion of the wall to the existing one. You may have a layer of OSB, insulation board or some other material covering the framing, so it needs to be the same depth. If you purchase a window with a mounting flange, installation will be alot easier, as you just screw or nail it from the outside and seal it with window tape along the edges. Place a piece of metal flashing above the window to run off potential rainwater, and install your siding. You will have to cut back on every other run of the siding to keep from having a vertical seam at the bottom of the window. Finishing the inside will require an identical wall finish as you have already. Post back if we can help further.