Concrete, gravel, both?

[JWN]

We are about to erect 2 new K-Series gourd racks with 3-inch square poles and are considering filling the holes with pea gravel instead of concrete. We live on the gulf coast with gumbo clay soil and during times of drought or dry conditions the ground cracks and recedes away from the concrete on the martin gourd poles that we are replacing. The poles remained erect, but at times they were in a concrete sleeve with large gaps around them. Has anyone else had this issue? Should we just stay with concrete? We welcome suggestions and advice.
Thank you!
~Jean

[Conrad Baker]

I would stick with the concrete. Even though you have some settling of the dirt around the concrete, you still want a solid foundation for the poles. The concrete would not allow any movement at the base, but if you only use gravel and you get even a little play, say around 2" at the base, that could mean a foot or two of movement at the top where the gourds are. They get a lot of lateral stress with the side to side motion from the wind, and that will tend to cause a less stable foundation if you only use gravel. Your gourd system is a lot heavier than the S&K plastic houses I use, and you will have a lot more weight that the base has to hold up. After a rain event with some heavy winds, your support might not be enough to keep your poles upright. I dig an 18" X 18" hole, then I put about 3" of pea gravel in the bottom of the hole for drainage, then pour the concrete in around the sleeve. I use duct tape to seal the bottom of the sleeve to prevent the gravel and concrete from entering the tube at the bottom.
I guess that using gravel as a "fill" around the concrete later as the voids appear wouldn't hurt anything.
My back yard is also clay after you dig down about 8 inches, and I also notice some cracking in the soil in the dryer months, but the concrete bases always stay solid and give the poles all the support they need.

[Waydog]

I have the same issue at my place...solid clay.and they form gaps around the sleeve in dry times. Im in agreement with conrad on keeping the concrete and digging a larger hole to accommodate more concrete. My setups are lightweight though, simple tri tels with sk lightweight houses that only stay raised 2 sections. With a heavier setup id go with his recommendation.

[Louise Chambers]

Jean, I've seen that too, at a public site I manage here in Corpus Christi - my thinking is that a bigger, bell-shaped pour of concrete around the sleeve for ground stake would be a good idea. The drought causes ground to shrink way from the concrete, and in a windy location, the slight movement of poles can make it worse. I tried to fill gaps with sand.

A better solution might be to water the ground around poles regularly if drought is ongoing. The pea gravel idea is something I hadn't thought of, I am not sure if it would be a good solution or not - I like the security of concrete.

[4th Gen Martin Fan]

If I read the directions for the K-series gourd rack's standard mounting, then the concrete actually holds a stake. This stake is filled with concrete to strengthen the area where the stake meets the concrete. The 3" pole then slides over this stake. In that case the pea gravel under the concrete would not be necessary.

The exception to that is the K-series gourd rack offers an optional ground sleeve which receives the stake. In that case, the pea gravel under the concrete would be necessary to prevent water from pooling in the ground sleeve. The ground sleeve receives the stake (which in turn still supports the pole.)

None of these options prevents the bad interaction between concrete and aluminum. Concrete makes the aluminum deteriorate faster. Hopefully not a major factor with the thicker aluminum stake or the optional aluminum ground sleeve of the K-series.
I am not sure if it is a galvanic reaction or if it is chemical corrosion of the aluminum.

I advocate the use of concrete as the support and have always used the bell shaped hole which Louise Chambers advocates.

[Chris Brown]

I'm putting up two North Star houses this spring and was planning on concreting them in. We have very heavy clay soil in the area and desiccation cracks open up when it is dry. They can run as much as ten feet deep and two inches wide. After talking to my mentor he recommended drilling three foot deep holes and just useing good packing gravel. He told me that is all he does now because in a big storm either way the pole can lean. With the gravel he is able to pull on the pole with a rope/truck and retamp the gravel to straighten the pole. With the concrete there isn't much you can do other then dig the whole thing up and start over. If the pole gets loose or the ground shrinks you can just retamp and add gravel the more times you do this the more solid you pole gets. So I'm going to use a T-handle style drill avalable at any hardware store and drill the hole as deep as I can or to the max deplth of my ground stake whitch ever comes first. This style of drill is a lot of back work but the advantages are one person operation and no heavy equipment required. Then for gravel I'm going to use crusher chips or sometimes called reject rock. It is the screenings left over from making crushed rock and gets very hard like concrete when packed. Finally the other advantage I see to this is that if the Martins don't agree with my choice for the location of the house after a couple years I can use a hand jack and pull the stake out in order to move it.
Hope this helps and good luck in 2014.

[JL Murray]

I have a K Series Rack and there is NO WAY i would even consider not concreting the ground stake in..

You bought a nice sturdy Rack so why not give it a nice sturdy Base CONCRETE IT!

[~Ray~Gingerich]

Yes, a nice sturdy base of concrete 10"dia x 38" then if you get a space later on pack it in with crush and run.

[JWN]

Many thanks to all of you for your suggestions and advise. We decided to go with concrete. Below is a photo. Chris please report back about your experience with the crusher chips this year. I am very interested to hear about your results.

[J Getting]

Did you put concrete in the ground tube? This makes the pole stronger.. Jim

[Chris Brown]

I will take some pictures when it tamp in the posts and through out the summer. In the fall once I see how wind has affected things I will post a report with pictures.

[dsonyay]

Yes.. be sure to fill that tube with concrete.

[Jack Gulvin]

Ask your local utility workers how they backfill the base of poles. Around here they use pea stone, not concrete.

[JWN]

Thanks for the tips! Yes, we filled the base of the pole with concrete. I am so impressed with the quality of the K-Series pole. Last year we had 2 pole failures with S & K poles and I never want to go through that again.

[Bernie Nikolai]

I've probably put up around 30 purple martin poles/houses over the last few years, using both concrete as well as well tamped pea gravel. BOTH work just fine! I am surprised the pea gravel does such a good job, but it does.

In our northern climate with frost heaving, etc. both concrete and gravel after a few years shift a bit and the pole can start to lean. But the solution is simple. In the early spring when the ground has thawed but the ground is still wet, just hook a chain around the pole about 3 ft. up off the ground and pull in the direction you want to straighten (very gently and very slowly naturally) with a tractor or a truck with a hitch. Both the concrete and the pea gravel poles straighten up very nicely.

Can't go wrong with either actually…..

[Dave Duit]

There are different types of concrete with varying numbers attached. When you go to buy your concrete, explain your situation. they may suggest a harder concrete that can withstand such weather conditions.

[~Ray~Gingerich]

I use a 5000 psi mix, when it's all mixed up I add a little high early just before pouring. Also when mixing be careful not to make it too wet, that weakens it. It shouldn't slosh off your shovel when you pick it up.

Sometimes when I dig my hole a little water seeps into the bottom but with a good strong mix I don't worry too much about that, especially when I add high early to the mix.

[RedSanders]

Jean,
Looks like your PMs will have a great guard dog. S/he appears to be a pit bull. For 15 years, my favorite walking partner, friend and protector was from a puppy give-away from a local pet store. He was part pit. Oh how I miss him.