Today as I drove home from work, I spotted a line of about twenty brand new streetlights, in gleaming aluminum, installed along the side of a certain stretch of highway. Something odd caught my eye: a few of them were definitely out of alignment with the rest – tipped this way and that by a degree or two. Of course, it makes sense that unless they are installed perfectly true, any small error in alignment at the base will be exaggerated at the top.
I have never seen proper highway streetlamps that weren’t all perfectly vertical.
So my question is this: How do they straighten an errent lamppost?
Do they:
a) Use shims at the base.
b) Use the boss’s pickup truck to gently persuade it into alignment.
c) Dig it up and re-plant it.
d) Do it right the first time (i.e. these were the evidence of drunken workers.)
or
e) None of the above.
In cold regions, anything not set 36-48" (or more) into the ground will “heave” when the ground freezes. “Frost heave” is why fences, foundations, walls, posts, etc need to be set down as much as four feet. When the ground freezes, it squeezes the post and heaves it up…or over, etc.
The might not be able to get straightened out.
Now, they might be driven 48" deep or more AND still heave, especially if the post is smooth with nothing odd shaped at the botton to anchor it, like a ball of cement would do. With many light posts, they are driven in and even though are very deep, can still be squeezed up by frost heave.
And next time you see some crooked ass fence, or something tilting oddly and can’t believe someone built it like that, chances are they built it straight, but didn’t put in into a proper footing that won’t be heaved by freeze/frost.
If these lightposts are tall and massive enough, they almost certainly have a sizeable concrete foundation, meaning that any brute-force attempt to straighten them will probably snap the pole from the foundation.
IIRC, many highway lights are specifically designed to break away from their bases when sufficient force is applied. This safety feature prevents serious injury to vehicle occupants in cases of wrecks.
Philster, I live in Joisey. I suspect that if freeze/thaw were such a problem for new light posts, I would have seen many crazy-angled posts in my Michigan days (I’m talking about the tall aluminum ones; not lights attached to telephone poles).
I figure that Carnac is right about the presence of a burly chunk of concrete belowdecks. Now I have a new question – if they plant the base first and then bolt on the post, how do they get even remotely close? I can’t see a bubble level being sufficient for the task.
Most posts like that have a four bolt flange base. Four threaded studs come out of the ground. On each is a nut, the flange of the post and another nut plus appropriate washers. This makes it fairly straightforward to tweak the verticality of the post if they need to.