Going to put up Rohn tower and need advice

mtand73

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I picked up a Rohn tower and plan to cement the base in.
Its a 24G 40 foot tower next to my house and I'm looking for advice on how big to make my hole for sure.
Thanks
 

n0esc

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Here is the tower guide from Rohn. Looks like you are looking at a 4x4x4 hole to allow for the proper sized drainage base, anchor and above grade clearance.

 

buddrousa

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My old Tower Manual list Rohn 25G 3x3x3 one cubic yard.
I have put these up with no more than 30 foot above a Rohn house bracket or guy wires every 30 feet per the manual with the max height of Rohn 25G being 180 feet. All 50 plus I have put up dating back to the late 70's are still standing. I still have my factory Rohn Gin Pole I bought in 1975.
 

n0esc

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My old Tower Manual list Rohn 25G 3x3x3 one cubic yard.
I have put these up with no more than 30 foot above a Rohn house bracket or guy wires every 30 feet per the manual with the max height of Rohn 25G being 180 feet. All 50 plus I have put up dating back to the late 70's are still standing. I still have my factory Rohn Gin Pole I bought in 1975.
Seeing that mtand73 is in Iowa, I'd definitely err on the higher end of the guidelines, maybe being able to get away with less if the tower is anchored to the house properly at height, but true freestanding in a northern state, unless at the far southern border of IA, there are some challenges we see up here that you don't fortunately have to contend with in your neck of the woods. Most of IA has a frost line that is 4ft deep. Frost heave and associated damage and pressures can be a very real problem. And the obvious enemy here in winters are ice and snow loading which will greatly affect the wind loading on the tower and any antenna structures. Something something ounce of prevention pound of cure. I'd rather dig a hole once than have to fight an insurance claim for a new roof and anything else a tower damaged on the way down. Especially if it ends up on someone elses property.
 

mtand73

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And with that info in mind whats your suggestion/recommended hole size?
I am thinking it will be attached to the house towards the top also.
 

mtand73

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Seeing that mtand73 is in Iowa, I'd definitely err on the higher end of the guidelines, maybe being able to get away with less if the tower is anchored to the house properly at height, but true freestanding in a northern state, unless at the far southern border of IA, there are some challenges we see up here that you don't fortunately have to contend with in your neck of the woods. Most of IA has a frost line that is 4ft deep. Frost heave and associated damage and pressures can be a very real problem. And the obvious enemy here in winters are ice and snow loading which will greatly affect the wind loading on the tower and any antenna structures. Something something ounce of prevention pound of cure. I'd rather dig a hole once than have to fight an insurance claim for a new roof and anything else a tower damaged on the way down. Especially if it ends up on someone elses property.
With that info in mind what is your suggested hole setup? I am planning to attach to house towards the top but I have VERY limited ground to guy it.🤔😬
Thanks for that insight by the way!👍
 

n0esc

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I don't want to stray too far outside my wheelhouse and give you an answer that isn't going to be correct. Couple questions I have is I guess I missed or assumed wrong. Is the tower you are getting a guyed version or freestanding. I originally linked you to the freestanding recommendations. The guyed guidelines are here in the catalog: http://www.rohnnet.com/files/2015_Rohn_Full_Catalog.pdf#page=26

How high is the anchor point you'd have available on the house? Guying guidelines for a 40ft tower anchor at 35ft. Engineered layout for wires are 32ft out from the base. Definitely not a tower or structural engineer so I can't give you a recommendation beyond take all of that into consideration before making a decision. The guyed tower uses a smaller hole and less concrete, but keep in mind that's assuming you have the proper three anchor points in place. Each change or omission will change the associated loads.

If you take a look at page 40/41 of the catalog, there are the house anchor and base section options as well. http://www.rohnnet.com/files/2015_Rohn_Full_Catalog.pdf#page=41

All of their engineering recommendations are online as well: https://www.rohnnet.com/files/25G_110MPH_B090091_ASSYPKG.pdf

All that being said, as I mentioned before, just take a look at the spot you are putting it, walk 50-60ft away and get an idea of what this thing could crush if it were to come down. First thing an insurance company is going to do in a contested claim is send a structural engineer to determine whether it was installed properly. Not trying to rain on a parade, and I'm as guilty as the next person for digging a 4ft x 18in round hole and tossing in a few bags of quickcrete to anchor a telescoping mast bolted at 20ft to the house and calling it a day. That was probably 25 years ago and as far as I know it's still standing, but in soft peat dirt we have here in MN, if the house anchors let go in the wind, someone would have been buying the neighbors a new car or gutters and roof at least. Good enough is only good enough until it isn't.
 

mtand73

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I don't want to stray too far outside my wheelhouse and give you an answer that isn't going to be correct. Couple questions I have is I guess I missed or assumed wrong. Is the tower you are getting a guyed version or freestanding. I originally linked you to the freestanding recommendations. The guyed guidelines are here in the catalog: http://www.rohnnet.com/files/2015_Rohn_Full_Catalog.pdf#page=26

How high is the anchor point you'd have available on the house? Guying guidelines for a 40ft tower anchor at 35ft. Engineered layout for wires are 32ft out from the base. Definitely not a tower or structural engineer so I can't give you a recommendation beyond take all of that into consideration before making a decision. The guyed tower uses a smaller hole and less concrete, but keep in mind that's assuming you have the proper three anchor points in place. Each change or omission will change the associated loads.

If you take a look at page 40/41 of the catalog, there are the house anchor and base section options as well. http://www.rohnnet.com/files/2015_Rohn_Full_Catalog.pdf#page=41

All of their engineering recommendations are online as well: https://www.rohnnet.com/files/25G_110MPH_B090091_ASSYPKG.pdf

All that being said, as I mentioned before, just take a look at the spot you are putting it, walk 50-60ft away and get an idea of what this thing could crush if it were to come down. First thing an insurance company is going to do in a contested claim is send a structural engineer to determine whether it was installed properly. Not trying to rain on a parade, and I'm as guilty as the next person for digging a 4ft x 18in round hole and tossing in a few bags of quickcrete to anchor a telescoping mast bolted at 20ft to the house and calling it a day. That was probably 25 years ago and as far as I know it's still standing, but in soft peat dirt we have here in MN, if the house anchors let go in the wind, someone would have been buying the neighbors a new car or gutters and roof at least. Good enough is only good enough until it isn't.
Long story short plan to bury the tower base section in concrete and as added precautions attach to the house as high as possible. Live in two story so should be close to top.
 

mmckenna

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Long story short plan to bury the tower base section in concrete and as added precautions attach to the house as high as possible. Live in two story so should be close to top.
Don't do that.

Purchase the correct base mounting hardware. You don't want to bury the base directly.
Even though the tower is galvanized, it'll corrode if buried, resulting in premature failure.
There are also weep holes in the bottom section that allow any moisture that condenses inside the hollow tower legs to get out. If you bury the section in concrete and block those holes, water will build up over time and corrode the tower legs from the inside out.

Contact Rohn and get the correct parts. Your life may depend on it.
 

prcguy

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A tower would be considered an additional structure and it may not be covered under a home policy unless you contact them and add it, paying an additional premium and possible inspection. Every insurance company is different and don't assume you are covered.

All that being said, as I mentioned before, just take a look at the spot you are putting it, walk 50-60ft away and get an idea of what this thing could crush if it were to come down. First thing an insurance company is going to do in a contested claim is send a structural engineer to determine whether it was installed properly. Not trying to rain on a parade, and I'm as guilty as the next person for digging a 4ft x 18in round hole and tossing in a few bags of quickcrete to anchor a telescoping mast bolted at 20ft to the house and calling it a day. That was probably 25 years ago and as far as I know it's still standing, but in soft peat dirt we have here in MN, if the house anchors let go in the wind, someone would have been buying the neighbors a new car or gutters and roof at least. Good enough is only good enough until it isn't.
 
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