What are you planning on trimming? Taking off some lower branches on your side won't hurt the tree if done properly...it will only annoy your neighbor. However, I would let him know what you are going to do before you do it, even if he won't like it. And I suggest that you model good neighbor behavior by telling him you know your back yard needs to be cleaned up, and then do it.

If the base of the tree is very close to the fence line, I would probably build up to it from either side and leave a little clearance. You can also choose to have the fence jog around it, but I wouldn't recommend that because that will result in your neighbor being able to legally claim that little area as his own some years down the road.

Branches hanging over your property are legally yours to trim in most places.
I think I would take the branches off at the property line to the height of the fance so the fence can be installed.

"If the base of the tree is very close to the fence line, I would probably build up to it from either side and leave a little clearance."

Leaving a partially fenced yard.
Just the thing for keeping dogs (and kids) in or out.

Cut the branches at the property line as needed to install the fence.
The only liability that attaches is if you trim so severely it damages the rest of the tree.

I have found that in instances like you can get all kinds of advice, however most if not all of it is just baseless opinion. This is a situation that requires the knowledge of an expert tree trimmer, they can advise how much to trim and since they probably will be local they will be very knowledgeable about local laws relating to this situation. It may cost a few dollars, but better to pay now and know for sure than to just guess relying on hearsay and end up in court paying for the removal of a dead tree and replacement costs of one of the same size.

How about consolidating whatever is 'junky' in your back yard to a smaller area and putting your 'spite fence' around that, leaving the borderline tree alone. That might lead to a better relationship with the neighbor when you improve his back window vista.

brickeyee-
Cut me some slack! I said "a little clearance." Given the growth rate of trees, one could reasonably infer that I meant a couple of inches, not a couple of feet...

Being a "tree trimmer" from the past( at least in PA)the property owner has legal rights from the ground up, meaning that you could prune back any and all branches that come across the survey mark straight up. You could NOT get on the other persons property when doing the work.

"Cut me some slack! I said "a little clearance." Given the growth rate of trees, one could reasonably infer that I meant a couple of inches, not a couple of feet..."

Obviously you do not own dogs.
Even a few inches with something as flexible as tree branches is a huge hole to a dog.

"I have found that in instances like you can get all kinds of advice, however most if not all of it is just baseless opinion. "

'Tree law' is reasonably constant across the US.
Anything hanging over a property line can be cut back to the line.

when we put up a fence around the back lot at work a LARGE tree belonging to a neighbor was about 25% over the line into our side. we took a chainsaw and cut vertically right down the trunk to the ground, then made a horizontal cut and removed that wedge. our fence butts right up against the tree where we cut it. the tree has a slight slant to it, so at 4' high the cut was skimming the edge, while at the ground it was a good 10" deep. that was 6-7 years ago and the tree is still plenty healthy. this is an old pecan tree though, some trees won't survive that type trimming.

i would cut whatever needed cutting to install your fence. as long as you don't kill the tree or step foot on his property, he cannot say a thing.

brickeyee-
Unless you have a Chihuahua, it's not getting through a 2" gap. You've got your opinion and I've got mine. I often think you give good advice. But you sometimes come across as a person who must be right all the time, and I think that can diminish the value of your advice.
.

...and just to be absolutely explicit, I'm talking about a small clearance around the trunk (or "base," as in my first post) since the OP can trim back interfering branches.

"Unless you have a Chihuahua, it's not getting through a 2" gap."

From the OP
"My neighbor has a tree that was planted perhaps 1 foot from the property line. ItÂs a gigantic evergreen (both height and width) and the branches cross the property line."

Ever seen a large evergreen?

They branches give the tree a decidedly cone shape, wide at the bottom and narrowing with height.

It would appear that that the branches at the bottom are over the property line.
If the fence is erected up to the branches, it will leave a very large gap that any dog will easily get through.

'Tree law' is reasonably constant across the US.
Anything hanging over a property line can be cut back to the line.

Generalized assumptions can end up costing thousands of dollars, a professional tree trimmer maybe a few hundred. Baseless opinion is just that unless you live in that jurisdiction and know their laws. Why advise someone based solely on your strongly biased opinions, some of the others here actually know a few facts, whether or not you are willing to accept anything other than your own "never wrong" opinion!

"'Tree law' is reasonably constant across the US.
Anything hanging over a property line can be cut back to the line."

How many states have you actually looked at?

I have at least 36.

It is reasonably constant with at least 36 of 50 states.

Half the time the tree services have at best a vague idea.

If you want an absolute answer pay an attorney some money, or look it up yourself.

Be warned it is often case (common) law.

It would appear that that the branches at the bottom are over the property line.

Appearances can been deceiving without pictures

I planted a evergreen in my yard about 5 feet from the fence, about 16 years ago. I really should have planted it a bit father away. I cut off branches that hit the fence, not all the way just enough so it doesn't touch the fence and the tree seems to be just fine. Best time to trim is in the fall/late fall. I would send him a nice letter letting him know you need to trim his tree a bit only to the property line to put up the fence and put up markers where the fence will be going up. He may appreciate the fence too since you don't get along well. Have you had a survey done or can you find the property markers? Just to be safe I would clearly mark where the fence will go so your neighbor sees it well before fence is started. Take pictures of the markers, before and after trimming the tree with markers in place.

the biggest difference in "tree" law is who is responsible for parts of the tree on another person's property. in most areas each property owner is responsible ONLY for the portion of the tree on their propery. in others, the "tree owner" is the person whose land the base of the tree is on and they can be forced to trim it back from the other person's property. the other big difference is who is responsible for damages should the tree/a limb/roots cause damage. in most areas again the person whose side of the line is where the damage happened is responsible(except in teh case of a known hazzard from a dead/decaying tree), very few areas have gone to making it the other person's problem.

as to a 2inch hole only letting a small dog thru, i have persoally watched a 75# lab mix chew a 4"Wx 5-6"H hole(1 plank) in a WOOD fence and then sqeeze her body thru it. if they can get there head thru easily, they can usually get their body thru. in the case of a chain link fence that gives some, a dog can easily get under a 2" gap. if ntohing else they will dig a small hole under it to aide in their passage.

Well, good thing that the OP isn't concerned about a dog, then...

The city just removed a huge tree from in front of my home, leaving a plot & said, even though it's a city street, it's my responsibility as the homeowner to repair that part of the sidewalk, out of pocket(will not get reimbursed), then I am worried that the semi-attached neighbor, who has moved in 5 yrs ago, continues to do construction & destruction of my health & home from heavy construction(no permits) & toxic fumes 24/7, with no relief when the police, fire, emts, gas/electric companies, plumbers, licensed contractors are hired to make repairs & I'm under drs' care for irreversible lung & nerve damage, high blood pressure & other ailments due to the stress, that they show no courtesy, common decency, continue to do construction all week & weekends all hours, that they had a back fence tied to my chain linked, aluminum slate fence & hired contractors to replace it with a vinyl fence, without informing me, until the contractors were sawing their old fence without regard for my fence until I spoke to them. Now I noticed these neighbors may be putting in a tree, bushes or fence in their front yard, blocking my air rights, or they're going to put a fence on my property, as my small brick fence around the front garden was moved in about 4 -5 inches from the corner of my brick porch as to avoid the attached neighbors from saying it was hanging over their property, they were measuring yesterday. What are my rights? What can I do?

Didn't you just offer advice on a similar issue on another 10 year old post?

I'm having a little trouble figuring out what the question is. This really should have been posted as its own thread, but in any case, the first sentence is 12 lines long and confusing. Your "rights", well there are a dozen different topics here - property lines, fence attachment, 'air rights' (whatever that may be, I've never heard of it), and noise. "No relief when the police, fire, emts, gas/electric companies, plumbers, licensed contractors are hired to make repairs..." Why are the police and firemen making repairs?

If you can try to boil this down to simpler terms it may help.

One thing I can suggest is that if people are doing work that requires permits and they are not getting them, you can certainly notify your local building inspection department because that's a violation of local ordinances. They should also be able to give you some advice on fence regulations in your area. If these folks want to attach a fence to a fence that is on your property, that is yours and not a common fence on the property line, they can't do that without your permission.

Why don't you clean your back yard of junk as a gesture of goodwill? This is why I live in an HOA. I can't stand looking at other people's crap. Neither can your neighbor.

anything on your side of the property line u can cut.