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Hanging a gate on a living tree

 
steward
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Is this a bad idea? I want to move my driveway gate in from close to the road down the driveway maybe 20 or 30 feet. While I haven't taken a tape measure to things yet, I see a cedar tree on one side of the driveway, and a much older oak on the other and the two trees are as such that using them as gate posts might work. They're right across from each other in such a way that the gate would sit practically perpendicular to the driveway when closed. I am considering hanging the gate from the cedar, and a latch would be on the oak.  The cedar is somewhat middle aged, and has a diameter of 9 or 10 inches and can certainly bear the weight. I understand that adjustments would need to be made as the trees grow over the years, and maybe this is reason enough not to do it. Perhaps I may get it working now, but in ten years things might be all out of whack and then I'm digging holes and setting posts anyway. I don't know, just thinking and tossing this idea out there. Has anyone done this or seen it done?
 
pollinator
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I did this with a ~ 12" spruce a couple years ago, using the sort of hinge hangers that screw in, so I hope that I may be able to unscrew them to adjust to tree growth. Gate is a 14ft tube and wire style cattle gate.

It hasn't appeared to bother the tree so far and sure saved some time setting a post in shitty rocky ground.


I secure it with a chain and padlock, so there is no problem if it shifts around a little bit... but I do not think it has budged so far.
 
James Freyr
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Cool, thanks for the reply. Is the gate still operating like it did at the beginning?
 
steward
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Look at a pintle hinge.  Either the screw in style or the long carriage bolt type.  Not sure which would be easiest to adjust.  

 
James Freyr
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Thanks Mike, that's what I was considering for a hinge. I may even be able to reuse the pintle hinge that the gate currently hangs on.
 
pollinator
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I would be concerned wind would affect function or security of gate - but of course that would depend on how windy it is there, or if these are stand alone tree's or buried in a forest.
 
D Nikolls
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James Freyr wrote:Cool, thanks for the reply. Is the gate still operating like it did at the beginning?



Yup; it's hung low and has a wheel on the end to keep it from dragging, all seems exactly the same as when installed.

Wind has not caused any problems, I don't see a lot of bending going on so low in a decent sized tree. This tree is at the edge of a 40-50ft wide belt of scrubby forest, on the wind-ward side.

Hinges are the lower of the two styles Mike posted.
 
pollinator
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Sort of a side-ways note here.

The issue with trees of course is that they grow and get wider, and absorb bolts and nails and such.  The fence lag bolts are relatively short and will eventually be absorbed entirely and then become the bane of anyone with a chainsaw or chipper.  How quickly they will be absorbed depends on species and conditions ... I have redwood trees with 3/4" growth rings which would render a lag bolt useless in as little as 5 years.

The folks at https://www.treehousesupplies.com found another problem ... that the sheer forces on bolts used for tree houses (much heavier than gates!) could deform the surrounding wood and pop the bolt out.  So they came up with TABS  https://www.treehousesupplies.com/Treehouse_Bolts_s/41.htm.  These are fancy things with a wide flange and long shafts and are designed to be absorbed by the tree (and thus become REALLY strongly attached).  

TABS are complete overkill for a fence support, but they are a great illustration of the issues we face when using mechanical fasteners on live, organic structures.
 
pollinator
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Eliot Mason wrote:The issue with trees of course is that they grow and get wider, and absorb bolts and nails and such.  The fence lag bolts are relatively short and will eventually be absorbed entirely and then become the bane of anyone with a chainsaw or chipper.


Wise advice. I refuse to use a chainsaw on the bottom 8 feet of a tree that is on the inner portion of a yard because of people putting in nails/screws/wire to hang things and the tree overgrowing them. I use a sawzall, even though it's a pain. Lessons learned the hard way.
 
Lorinne Anderson
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As to the tree "absorbing the bolt"; could it not just be "backed off" a bit every year? I know the gate screws I use are a good 4-6 inches long...
 
Douglas Alpenstock
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The bolts/lags certainly could be backed off every year.

The only thing I worry about is the effect on the tree. Does opening the wound every year open the door to disease or insects? I don't know.
 
Eliot Mason
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Douglas Alpenstock wrote:The bolts/lags certainly could be backed off every year.

The only thing I worry about is the effect on the tree. Does opening the wound every year open the door to disease or insects? I don't know.



Arborists tell me that the sample cores they like to take don't bother the tree.  Sample cores are significantly smaller than a 1/2" lag bolt, but they also go much deeper.  I think the larger issue is the time of year... if the bolt is adjusted when the sap is running, the tree has no problem filling the void.  In the dead of a frozen winter... probably not.  I think the other caveat is "healthy tree" - a sick tree might be pushed over the edge, but you won't know how sick it is until its dead...and then you just put in a post.

 
Eliot Mason
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Mike Haasl wrote:Look at a pintle hinge.  Either the screw in style or the long carriage bolt type.  Not sure which would be easiest to adjust.  



My reaction to this is "you HAVE to use the lag bolt style", but it really depends on the tree diameter.  A lag bolt goes into a relatively short hole you've drilled and then your adjustment is limited to one full twist of the threads.

the bolt and nut type ... whereas the lag bolt use threads to hold on, the bolt style effectively squeezes the post between the nuts.  On a tree you'd have to drill all the way through, then tighten it down..  At that point it would behave almost like one the TABS for tree houses...the tree would do its best to grow over the washer and then the nut, and any adjustment would require hacking at the tree to free up the washer and nut.   I think that would be hard on the tree.

Also, the long bolts get pricey.  If the tree is larger than 12" you might not be able to get one of these off the shelf...
 
pollinator
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> adjust bolt....

Well, when one side of a gate moves (you adjust it at the hinge) the other side will move too (at the "latch").  That OK?   How big do you think that tree will grow?

My take. Adjusting it may be possible, but it might not work as planned. IOW, a hassle. And a hassle that is like a "balloon payment" - everything nice for a couple  years until... The other shoe falls. By which time you have forgotten your ingenious Plan. And by that time lots of things may have changed and "adjusting" may not be quite so clean and clear.

The more I think about the more I think it would be much better to use the tree as some kind of lateral support but not as the main structure for the gate post. That should allow setting a bi-pod (w/center post to mount the hinges) on the ground with relatively little penetration; then use the tree to take the torque of the hanging gate with a long rod, lag or bolt. Well, there's need for a force diagram and anchor design. But because of the speed w/which trees can "move" and the ease w/which we forget and stuff like that, my inclination is to keep that gate post away from the tree.

A note on those pintle hinges. They _really_ like to rotate (after installation). So keeping the bolt oriented in the plane of the closed gate will help keep the gate hanging more or less where it started out.  As opposed to installing the bolt (into something) at right angles to the plane of the closed gate. That gate will sag instantly as the bolts rotate. Yes, I've done both. There is still sag when the gate is opened, but... Well, take your choice. I guess an argument could be made either way.

That other thing is cut one of the hinge pins 1/4-3/8" shorter than the other so you don't have to get them both in at the exact same instant when hanging the gate. OR set the top pintle that much higher than "right". That will let you set the top pin first, but it also means that top pintle carries _all_ the weight - and the bottom pintle is just there as a guide. Both the gate frame and the hinge post have to be ok with this.


Cheers,
Rufus
 
D Nikolls
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Rufus Laggren wrote:> adjust bolt....

Well, when one side of a gate moves (you adjust it at the hinge) the other side will move too (at the "latch").  That OK?   How big do you think that tree will grow?

My take. Adjusting it may be possible, but it might not work as planned. IOW, a hassle. And a hassle that is like a "balloon payment" - everything nice for a couple  years until... The other shoe falls. By which time you have forgotten your ingenious Plan. And by that time lots of things may have changed and "adjusting" may not be quite so clean and clear.

The more I think about the more I think it would be much better to use the tree as some kind of lateral support but not as the main structure for the gate post. That should allow setting a bi-pod (w/center post to mount the hinges) on the ground with relatively little penetration; then use the tree to take the torque of the hanging gate with a long rod, lag or bolt. Well, there's need for a force diagram and anchor design. But because of the speed w/which trees can "move" and the ease w/which we forget and stuff like that, my inclination is to keep that gate post away from the tree.

A note on those pintle hinges. They _really_ like to rotate (after installation). So keeping the bolt oriented in the plane of the closed gate will help keep the gate hanging more or less where it started out.  As opposed to installing the bolt (into something) at right angles to the plane of the closed gate. That gate will sag instantly as the bolts rotate. Yes, I've done both. There is still sag when the gate is opened, but... Well, take your choice. I guess an argument could be made either way.

That other thing is cut one of the hinge pins 1/4-3/8" shorter than the other so you don't have to get them both in at the exact same instant when hanging the gate. OR set the top pintle that much higher than "right". That will let you set the top pin first, but it also means that top pintle carries _all_ the weight - and the bottom pintle is just there as a guide. Both the gate frame and the hinge post have to be ok with this.


Cheers,
Rufus




My gate gets around 3 of these problems. My solutions will not work in all cases..


1) The latch is a chain, no precision fit needed.

B) There is a wheel supporting the latch end of the gate, so hinges don't have a turning force on them.

III) The lag-bolt portion of the hinges were installed in the tree, with the top one upside down; the upper socket side of the hinges was left loose on the gate, and tightened after placing the bottom socket on the pin, and adjusting the top socket to fit.
 
Mike Haasl
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It might hinge upon how fast your cedar is going to grow.  If it puts on 1/8" of radius each year, you could set the business end of the lag 2" from the bark and then not worry about it for 16 years.  Or back it off a turn every other year to stay ahead of it.  As long as it doesn't "stick" to the lag extremely tightly, I'd think that backing it off each year wouldn't do much ongoing damage to the tree.

The long threaded bolt would still work if you are ok with it becoming permanently embedded in the tree, and if it grows slowly.  You said it was a 9-10" tree.  So you could drill through it, just barely tighten the nut on the far side and snug it down on the gate side.  If it's a 12" threaded bolt you'd have 2 inches sticking out the gate side.  The tree grows over it and you're fine until it puts on 2" of radius.  If the tree grows slowly enough, that might be just fine.  Or weld an extension on the bolt so you can have it stick out 4-6" on the gate side.
 
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