You need to also consider 1 Corinthians 3 to understand what Paul is teaching there.
For those who are saved build upon Christ the rock of their salvation, how they build is key to whether or not they receive a reward.
Building with the wood, hay , stubble leads to destruction but not of their salvation.
1 Corinthians 3
5 Who then is Paul, and who is Apollos, but ministers through whom you believed, as the Lord gave to each one? 6 I planted, Apollos watered, but God gave the increase.
7 So then neither he who plants is anything, nor he who waters, but God who gives the increase.
8 Now he who plants and he who waters are one, and each one will receive his own reward according to his own labor.
9 For we are God’s fellow workers; you are God’s field, you are God’s building. 10 According to the grace of God which was given to me, as a wise master builder I have laid the foundation, and another builds on it. But let each one take heed how he builds on it. 11 For no other foundation can anyone lay than that which is laid, which is Jesus Christ.
12 Now if anyone builds on this foundation with gold, silver, precious stones, wood, hay, straw,
13 each one’s work will become clear; for the Day will declare it, because it will be revealed by fire; and the fire will test each one’s work, of what sort it is.
14 If anyone’s work which he has built on it endures, he will receive a reward.
15 If anyone’s work is burned, he will suffer loss; but he himself will be saved, yet so as through fire.
