I think that the ESV in this particular place can be a little confusing. The Greek text literally says, "thus yet as through fire." I think Hodge says it best:

If the materials used by a spiritual builder stand the test of the day of judgment, he will receive the reward of a faithful servant.

If the work is burned. That is, if the materials used by any builder do not stand the test of that day.

The builder will suffer loss. That is, he will lose his reward.

The builder will be saved. Just as someone who has built his house of combustible materials may escape when the fire comes, yet his property is lost, and all his labour comes to nothing. The apostle is speaking here about those teachers who, although they retain the fundamental doctrines of the Gospel, combine them with error. This is clear from verse 12: 'If anyone builds on the foundation.' It is not enough, therefore, for a minister to hold fast to fundamental truth; he must take heed what he teaches in connection with that truth.

—Commentary on 1 Corinthians

Jim

Jud 1:3 . . . contend for the faith that was once for all delivered to the saints.