I'm pretty sure my roof has no waterproofing

Went on my roof today. Found a broken tile about 4 feet from the edge. Removed it. There is no waterproof layer. Just exposed plywood and felt. Does the whole roof need to be redone?..

Not yet. Replace the broken tile.

The roof does not need waterproofing?

The felt is your waterproofing. Looks like the tiles been broken quite awhile and the felt deteriorated from exposure.

Were you walking on your roof or did you inspect it from a ladder? Concrete tile breaks easily under foot traffic.

I was very careful not to break tiles. I crawled on all fours. Today, I was the first person to be on my roof since it was built nine years ago.

Tough decision. The type of tile you have uses water channels on the edges. As long as they stay clear and no tiles are broke, they work fine and seldom get more than ‘moisture’ in the roof deck.
In the case of wood decks, the wood could get moist and dry out 100’s of times for 100 years or more and it would never be an issue.
In the case of plywood which isn’t the best material for a tile, metal or slate roof, the moisture can cause problems and delamination at some point.

As a rule for the decision, when the tile keep/constantly break and create numerous leaks, it’s time to replace. Also, when the channels keep clogging and directing more water under the roof than down the roof and causing leaks, it’s time to replace.

It’s going to be a judgement call. Replacing the one tile could solve all your problems for the next 2-20 years. Hard to say from here.

You can call my cell # after 8am, eastern, if you want more answers. I’m not really a typist.

Felt paper is not a waterproofing agent. Felt paper is a moisture barrier.

By the looks of the felt paper in place, it is “dried out” and is curling. Perhaps this condition is particular to only this location where the tile is broken and UV rays are deteriorating the felt paper.

I agree with Tinner. Replace the broken tile and keep an eye on it.