I have a 35 foot aluminum light pole that has 4 bolts holes in the base of the pole. I need to know how deep and wide should I pour the concrete into the ground. I'm not going to use the light pole for a light, I'm recycling it to make a flag pole. The base bolts holes are 8 inches apart in a square. The base bolts measure 11.5 inches diagonally. I want to be able to fly two flags from the pole and I want to make sure that I have enough concrete in the ground to support the pole, two flags, high winds, ect. I live in western Kentucky.
How deep of concrete base do I need for a 35 foot
lightpole
Related Solutions
You may want to consider one of the various style of commercial bracket assemblies designed to mount antenna masts onto chimneys and concrete columns. Here are some examples:
My estimate from the information given so far is that the nearly 18 foot high pole is not adequately anchored just by embedding the end of it in smallish block of concrete and a couple of U-bolts into a plank at ground level. (The block and u-bolt locations are smallish when you consider the overall pole lever arm length).
This thing should have a set of three guy wires coming down from about the 13 or 14 foot level that come down at angles to the ground and are anchored to their own piers of concrete in the ground. The bottom end of the guys would want to be out 13 to 17 feet from the bottom of the pole and spaced radially around the pole at 120 degree spacing.
This procedure will ensure that a high force wind will not take down your bat house and crash it upon someone or some other property.
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Best Answer
There are lots of variables that really need to be evaluated by a Registered Engineer but you can use this site for a quick evaluation:
Flag Pole Calculator
Of course you'll need some details to figure the lateral force at the top of the pole, this comes from the size of the flag and the expected windspeed it will encounter. You'll also need a figure for the soil characteristics.
Again I encourage you to consult an engineer since the last thing you want is for this thing to come crashing down and injure or kill someone.