The short answer is this: Utah building code allows only 2 roof layers on a home. A third layer is not allowed and the roof will need to be stripped down after 2 layers.
We recommend tearing off the existing roof if there has ever been a history of leaking or if the first layer is in extremely poor condition. Covering up a problem will never result in the fixing of a problem.
What roofs are good candidates for a re-roof. We only recommend roofs that are fairly smooth and have never had a history of leaking.