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Q.Why it is that most exterior doors swing in rather than out? I can think of several reasons why they should swing out: (1) It is more difficult for the wind to get around a door that swings out since it is pressing the door against a seal rather than away from it. (2) An out-swinging door can overlap the sill at the bottom so the water can’t get in, and (3) an out-swinging door can be pushed open easier from the inside in an emergency.

A.Gordon Tully responds: There are many reasons for having in-swinging exterior doors on homes. First, let me respond to your remarks.

1) When winds blows over the roof of a house, it creates negative wind pressure on the lee side (opposite the windward side). This negative pressure is just as strong as the positive pressure on the windward side.

2) A door that overhangs the sill would be difficult to seal against air leakage. A properly detailed door has a bulb weatherstrip at the bottom resting on a projecting sill that slopes away from the house. The only advantage of an outswinging door (and it is a real advantage on occasion) is that there is less sill surface exposed to the weather.

3) Out-swinging doors with "panic hardware" are required by commercial codes. But on homes and small offices, most codes allow egress doors to swing inward, because they have few occupants, most of whom use the place often enough that they will habitually expect the door to open in.

Here are a few additional reasons I tend not to use outswinging doors:

1) An outswinging door must either be specially finished at the top, or protected by a deep porch. Otherwise, it will quickly deteriorate in the weather.

2) Outswinging doors can be a hazard and a maintenance problem. It is easy for the wind to rip an outswinging door off its hinges. If the door opens off a small porch or stoop, an outswinging door could tip a visitor back down the front stair, especially if the wind catches it.

3) In many climates, you need a screen door, so you will have one door opening in and one opening out. Since the screen door is designed to shed water, is more transparent to the wind, and has less impact if it should hit a visitor or slam against the wall, it should be the one to open outward.

4) In snowy climates, you can easily be trapped in the house because you can’t open the door against the snow or ice (it has happened to me). I would consider an unprotected outswinging door to be a lethal hazard in a snowy climate (the same can be said for outswinging storm doors).

5) Finally, it is easier to pry open an out-swinging door than an in-swinging one since there is no stop protecting the lock. Also, since the hingepins are on the outside, you can simply knock out the pins and remove the door unless you use special hinges with nonremovable pins.

Gordon Tully is an architect in Arlington, Massachusetts.