Note 6 at 1 Cor. 3:15: This whole parable of Paul is about Christians. He makes that clear in verse 11 when he reveals that the foundation of this building is Christ. Therefore, when he speaks of those who used the wrong building materials suffering loss, he is not speaking of them being damned. He goes on to say in this verse that they themselves will be saved.

So, he is describing Christians who lost their rewards because they acted from the flesh (see note 3 at Rom. 7:18, p. 790) instead of the Spirit. Does this mean that there will be some second class citizens in heaven? No! (see note 6 at Mt. 10:42, p. 228)