Once the outer layer of your roof has been breached, the water will get in and start to damage the underlying structure. Much sooner than you think the rafters will begin to collapse and you will be facing a large repair bill. Far larger than it would have been had you repaired the leak straight away.
The water that enters your roof space won´t stop there. It will continue to drip and creep into other areas of your building. Eating away at the insulation and allowing mold to develop that will rot anything made of wood and rust metal. Running along with the wiring and damaging your electrics.
If you have family members who have respiratory problems, for example, asthma, the mold that grows could make them extremely ill. It is also not good for healthy individuals.
Once your roof is open to the elements, the rate of damage accelerates. Plus, should there be a fire your roof will no longer contain it as it would do if it were still structurally sound.
As you can imagine, all of these structural issues will harm the value of your home. If a potential buyer walks in and smells mold or mildew, they will likely walk straight back out again. Very few people are prepared to take on a property with a leaky roof. They are only too aware of the fact that far more damage has been done than is visible.
Fortunately, the answer to this issue is simple. Provided you get your roof inspected regularly any leaks can be spotted and repaired fast. Before too much expensive long-term damage is done.