Calculating Picket Spacing:
I built sections of fence with pickets that aligned with
both ends of the rails. My initial thought was to install the
fence sections between the fence posts (so the posts
would be fully visible from the front), but as I installed the
fence my approach changed.
There are two basic cases in fence picket layout:
1. Picket quantity exceeds number of spaces. To
illustrate, look at your hand. You have five digits
(hopefully) but there are only four spaces between the
digits. My fence sections had 12 pickets and 11 spaces, which
was not the best idea. But this approach is necessary
sometimes, such as with garden gates.
2. Picket quantity equals number of spaces.
There are two cases within this situation:
- Full space on one end
- Half-space on each end. This is what I should have done.
To determine the exact spacing of the pickets, I had to do
a little math. There were some given quantities: The picket
width (5.5") and the length of the fence rails
(96"). I estimated a starting value for the spacing
distance by measuring the width of the smallest dog, (not a
simple task) which was just under 4 inches. So to be on the
safe side, I chose 2.5" as the starting dimension.
Now I can do this math in my head. I saw that the picket
plus the space equaled 8 inches, which meant 12 pickets and 12
spaces. Had I been thinking clearly, I would have simply
chosen the 8 inch pattern and figured out how to divide up one
of those spaces so half of it appeared at each end of the
rails. But I chose the sub-optimal approach and proceeded to
compute the exact spacing for only using eleven spaces. It
looked like this:
12(5.5) + 11S = 96 where S is the length of
the space between pickets.
Solving this yielded:
- 66 + 11S = 96
- 11S = 96-66
- 11S = 30
- S = 2.727 inches, which I rounded up to 2.75"
Thus, the length of the repeating pattern (i.e. from the
start of one picket to the start of the next picket) was 5.5 +
2.75 or 8.25 inches. This worked great! Once installed, the
pickets were perfectly uniform, square and parallel. The fence
sections really looked professional. Until I installed them.
A general formula could be devised for fences like this:
PX + S(X-1) = L
- X = Number of pickets
- P = Picket width
- S = width of open Space
- L = Length of fence rail
Of course, you can only have one of the four quantities
unknown, that would normally be S, the open space amount.
Here you can just chose a spacing that, when added to the
picket width, is divisible into the length of the rail.
(P+S)X = L
But for the preferred assembly technique (half a space at
each end of the rails), the only complication arises in
determining the starting point for the pattern of picket
layout. And the starting point is simply a distance one-half
of the open space width (S/2) from the end of the rail.