You've been watching construction over at your neighbor's house, and now you are realizing that they have crossed over onto your property with their project. Now, what do you do?
Make Sure First
Don't rely on your vague notion of boundary lines to make your judgment on your neighbor's building project. Check on your own property deeds or with the council office to find out precisely where that boundary really is. If this information is not available or you simply can't make out the lines on your own, you can hire a professional residential property surveyor to do the investigation for you.
Remember, you have a right to protect your boundaries and that usually also includes a certain amount of space on their side as well. In other words, if your neighbor’s new shed is literally up against the line of the boundary, you still may have a case against them.
To maintain good relations with a neighbor, you may want to consider doing nothing. If his new shed is a foot on your property and it genuinely doesn't impact your own use of the space, you may not want to press the issue simply because you can.
One thing to remember with this choice is that legal action left too long will be less successful than anything you do immediately. If a structure or fence is over the line, but was not a concern for 7 years, then your claim will lose some credibility. If you decide to ignore it, you should expect to ignore it permanently.
Talk to Them
Nobody wants an expensive legal battle so you can try to come to an agreement unofficially between you. If the structure or fence can be moved, that is one option or you can come up with something that works for both of you. Perhaps you can have access to that new pool occasionally, or store your weed trimmer in the new shed. Just make it clear to them that they have crossed the border and you do have the right to legal action if you can't agree on something.
Or you can simply let them know that the problem exists just so that it's out in the open and known to both parties. It might come in handy later to remind them of this infraction when you need a favor or something else has to be arranged between you.
Take Legal Action
Hopefully, you won't simply jump to this option, but it is definitely within your rights to do so. If you take this route, prepare for a lengthy process and plan on having as much paperwork as possible to back up your claim. Your word against theirs isn't going to hold up in court to establish a boundary. You'll need ownership documents as well as an official map or survey of the property.
The specific process will vary by region as the local laws involving property boundaries are not universal. Talk to your council office and they can probably tell you the right steps or help you contact a lawyer that specializes in property disputes.
Take time to consider your options. Creating a permanent rift in any neighbor relationships because you insisted a shed be torn down may not be worth gaining back a few square feet of property.