Doom 2 - Double door activated by switches

[SaintsRLFC Tom]

Attempting to use two small doors next to each other, when one switch is activated one of the doors open however both must be open for the player to advance. Have connected both doors to their individual switch however when the switch is activated the door dosen't open.

[Simomarchi]

When you open a door, the ceiling of the door is raised to the height of the lowest nearest ceiling minus 4 map units.

Having that your doors are connected, both have the nearest lowest ceiling at the same height, therefore they cannot raise because they are already at the height of your lowest ceiling (the one of the other door).

In order to solve your problem you simply have to place your doors at a distance of 1 map unit from each other, with the 1 mu sector that has a ceiling height equal to the one of the next room

[Empyre]

Another idea is to have the "doors" start with the floor at the ceiling height and have each switch lower the "door" to lowest floor, so they open down, instead of up. This would be useful if you want the room behind the two-part door to be completely sealed until one of the doors is open.