Advice requested

[quakerboy]

2. The tile

Was glued directly to the subfloor. The tile is now gone. Based on the very limited location, size, and shape of the damage to the subfloor, I am fairly certain it does not predate the tile. And the dark color of the wood leads me to believe that the damage may extend into the wooden threshold that the damaged flooring area touches. Now the question is what next.

We already have the replacements for the tile flooring, and everything we need to do it correctly this time. However, I wasn't expecting the subfloor damage.

So it seems to me that the first step is fixing the little section of damaged subfloor. A quick online search netted me recommendations to remove the whole section of subfloor and replace it. Which would be financially unfeasable, as it would mean ripping up half my livingroom floor. So I am wondering if there is a simpler way to deal with this 1 square inch damaged section than replacing the whole underfloor.

Given that I believe the wooden threshhold is damaged as well, replacing that seems like a good plan. Its an unexpected cost, but significantly less so than reflooring our entire living area. We were thinking of a metal one as it seems much more likely to last a while than another wooden one, given that we live in an extremely rainy area. I am willing to be persuaded on that, however. I just realized that a metal one might not be the best for temperature insulation purposes. Maybe they have other issues that I am not aware of.