Foundation for Flag Pole or Purple Martin House

[bookman51]

This only slight off topic, but I am thinking of putting up a purple martin house. I used to have one where I used to live. I used the pipe that used to hold the big satelite dish the previous owner had. I had not idea of the foundation. So what do folks recommendation for the foundation for purple martin house. How deep in the ground for the pipe and how much concrete? We get pretty good winds where we are located.

Thanks

Bookman

[Torque1st]

Just dig a hole deeper than the frost line with sides straight up and down at least 8" in diameter. Get a piece of pipe that will accept the pole 6" longer than the depth of the hole with a bolt thru it 6" from the bottom end and drive it into the bottom of the hole so water has somewhere to drain to. The bolt thru the pipe gives your pole somewhere to bottom against. Then pour the hole full of concrete. You can also notch the pole on the bottom where it sits on the bolt to keep it from turning.

[bookman51]

Thanks, I think frost line is about 36" here. Looks like I need a good bit of concrete. Good idea about the bolt and the notching.

Thanks again.

Bookman

[Torque1st]

Depending on your diameter it is not bad. An 8" hole 36" deep will hold just a bit over 1 cubic foot (1810cu-in). 1 cubic foot = 1728cu-in. The pipe will take up some volume. I believe the bags of sackrete are marked for how many cubic feet they make.

[bookman51]

Thanks, A big help. Next step is hoping I can attack some purple martins. I enjoy watching them. I guess the reviews are varying in how much they help with the mosquito problem, but still enjoyable to watch.

Bookman

[Torque1st]

Good luck!

[krooser]

I built a 20' flagpole back in '87 for my racetrack... moved it when I closed the joint. It's still in front of my old house, The pole sits in 18" of concrete about 1' in diameter. no need to worry about a frostline since it will simply "float" like a concrete slab...

[Torque1st]

If the concrete does not go below frost line the frost heave will "float" it resulting in a leaning pole especially if there is a side force on a pole due to wind. There is a reason for code requirements on footings etc to go below the frost line.

[krooser]

Originally Posted by Torque1st

If the concrete does not go below frost line the frost heave will "float" it resulting in a leaning pole especially if there is a side force on a pole due to wind. There is a reason for code requirements on footings etc to go below the frost line.

Well I'm not so sure there are code requirements for flagpoles but maybe there are where you live. I can snap a pic of my old flag pole and it looks like it's mounted in viagra... stands straight and tall and was installed in 1989.

Even here in chilly Wisconsin a frost heave MIGHT be two inches... c'mon this ain't a building it's a flagpole. Next thing you'll have to get an OK from Washington and use stimulus money to build it.

[hawkeye2]

Originally Posted by bookman51

Thanks, A big help. Next step is hoping I can attack some purple martins. I enjoy watching them. I guess the reviews are varying in how much they help with the mosquito problem, but still enjoyable to watch.

Bookman

I assume you meant Attract

[buening]

I can design and detail it to withstand hurricane force winds

It is up to you if you want to put it at frost line or not. You really aren't looking at that much more money to put it down 3'. Consider the headache trying to fix it if it were to heave from freeze/thaw action. I'd recommend some compacted gravel at the bottom of the footing, which is common with any kind of concrete on grade construction.

Two inches of frost heave on the outer edge of a small 3' deep footing for a 20' flagpole would result in the top of the pole moving roughly 3.5', to give you an idea of the magnitude of movement at the top compared to a small amount of frost heave at the footing. The taller the pole, the more obvious it will be that it has moved.

[Gary S]

I cheated when I put up my flagpole. I had a 65 ft Spruce tree that I had to get removed. After the tree was gone, I simply drilled a hole down into the stump about 10 or 12 inches and stuck the flag pole in it. Then I shaped the stump with a chain saw and stained it with deck stain. I figure it will last 10-15 years before it rots and at that time it should be much easier to remove so I can pour a cement pad to replace it.

[Torque1st]

Do it right the first time...

[Bevis]

...so should he put a ton of rebar in the hole too.

[Torque1st]

Originally Posted by Bevis

...so should he put a ton of rebar in the hole too.

Not really, there is no need with that small diameter.

[bookman51]

I talked today with a local fellow (74 years old) with probably half a dozen purple martin houses. He went down 2 and a half feet here and used two sacks of concrete. The poles stayed up during the bad winds and hail last spring, but he had some damage to the houses. I probably will do 3 feet and perhaps a 12" diameter holes.

Might as well do it right the first time, and we do get some pretty high winds here in Nebraska, along with some pretty cold weather.

The fellow said the martins are here now, so I better get going now if I am going to "attract" them.

He also had a sparrow trap and he said he kills 400-500 of them a year. Perhaps that is that I need to attack.

Thanks for the help.

Bookman

[Steve in Mi]

The martin houses left by the PO were mounted on 4"X4" wood posts. The post base is maybe 200 pounds of concrete with 2 - 3"X3"X3/8" angle sticking up out above ground level. There were two large bolts holding the post to the angle iron and removal of one bolt allowed the post and martin house to be lowered for maintainence (paint, clean out nest boxes). A rope and a pole made it easy for two people to raise and lower the bird house but in a pinch, one person could manage.

The 16 hole martin houses are gone now after 32 years but I dug up one post anchor and saved it hoping to obtain another martin house or perhaps a TV antenna to mount in/on it.

[bookman51]

I put in the base of the purple martin pole today. Local Menards had 60 pounds sacks of concrete mix on sale for 4 for $9. So I got 4. I dug down four feet, put two or three inches in coarse gravel in. Then I had a railroad tie plate so I put it down there. I put in the pipe on it and then put in another five or six inches of coarse rock. I any water in the pipe should drain out in the coarse gravel. Then I used three of the sacks of concrete. I continually checked it with a level to see if it is vertical. Probably pretty hard to get it exactly vertical, but it tried. However, any slight variation down low will result in a lot of difference at the end of a 15 foot pool. I will wait for couple of days for it to cure before I put the house up. Supposedly the scout purple martins are already here, but I will probably be getting the younger ones who do have a nesting place to which to return.

We do get pretty good winds in central Nebraska with 40 or so mph gusts recently. The pole probably will handle it, but the house might not.

Thanks for the help.

Bookman

[Torque1st]

You will have a HD foundation that will last for many years. -Congratulations.

[Bevis]

Originally Posted by Torque1st

Not really, there is no need with that small diameter.

I just put that as a joke...with all the engineering talk over this simple project.