The old fence is like a part of a house, and part of the landscape. The problem is that the old fence can be very dangerous, unstable, and if the fence is really old, it's hard to repair it to things like good standards.
They also tend to be surprising if new neighbors want to replace them, so it's a good idea to talk to your local fence contractor before you need to enter damage control mode. Are you looking for the fencing in Sydney, you can check out via the web.
Signs of a fence that needs to be replaced
The signs are not always clear. Some fences are so hard that they look OK-ish, but there are structural problems that you need to check:
Supports loose: If the fence moves, it's a sign that the entire fence is under pressure from gravity. The fence can be completely revoked overnight. They can also carry a lot of garden soil, leaving weeds and parasites.
Wet area: If the support becomes moist, they can also move, which can draw parts of the fence and affect other parts as well.
Mushrooms, algae and foul marks on a wooden fence: The fence treatment has reached an expiration date. These factors will progressively damage the wooden fence section.
Cross beam out of position: Arching is unusual, but if the cross beam is not parallel, something else has moved. This is a structural problem that may be corrected or not. Note: On steel fences, nothing should be out of alignment.
Termites: Signs of termites mean the fence is really in trouble. This may be very old, and this pesky insect can do great damage quickly. Try to identify a specific area, because you need at least a replacement fence in the area.