Iowa Code § 327G.4: Specifications.

1. All fences shall be not less than fifty-four inches high and may be of any of the following types:

a. Not less than five barbed wires, properly spaced.

b. Not less than three barbed wires above and not less than twenty-four inches of woven wire below.

c. Entirely of woven wire.

d. Five boards properly spaced.

e. Any other type which the fence viewers of any township through which it passes may determine as efficient as any of the above types.

2. Each of the above types shall be securely nailed to posts firmly set, not more than twenty feet apart for the first three types, nor more than eight feet apart for the fourth.