If your roof is leaking, in many cases it is safer and can possibly be cheaper to replace the whole roof rather than try to simply fix the origin of the leak. This is due to the fact that if there is a leak, there could be further damage between the multiple layers of a roof that could promote more significant damage such as mold. Whether the entire roof should be replaced due to a leak or not would also depend on the severity of the roof’s leak, and a complete roof replacement may not be necessary.