I have a little different take on this verse. If you look at the verses that precede verse 12, it says this:
“For we are God’s fellow workers; you are God’s field, God’s building”
Also, in the verses following verse 12, it says this:
“Don’t you know that you yourselves are God’s temple and that God’s spirit lives in you? If anyone destroys God’s temple, God will destroy him; for God’s temple is sacred, and you are that temple.”
Considering those verses, look back at verses 11-13:
“For no one can lay any foundation other than the one already laid, which is Jesus Christ. If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw, his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man’s work.”
Notice that the word in bold, “work” singular, not “works” plural. I think these verses refer to the most important “work” we will ever do and that is the building up of ourselves in Christ. How then do we “build” ourselves? Which of these materials do we use: gold, silver, costly stones, wood, hay or straw? I think Paul is saying none of the above! We can build a life based on these “worldly” materials but will they last? The first 3 can withstand fire, but can they withstand the fire of the Judgment? The Bible tells us that nothing of this world will survive that day. Some of those in the church at Corinth, and in the church today, were building their lives on material things. Why else would Paul have compared their wealth versus his poverty in 4:8-13?
If we consider the building materials mentioned as figurative, what then are the things of “gold, silver and costly stone” and what things are “wood, hay and straw”? Look deeper into the entire passage and you will see. This section of Paul’s letter is an admonishment to the Corinthians for causing division in the church by being too “worldly” in that they were putting too much emphasis on one man’s teachings over another. Look at verses 3-4, “You are still worldly. For since there is jealousy and quarreling among you, are you not worldly?“ For when one says “I follow Paul” and another “I follow Apollos” are you not mere men.” There was then jealousy (v3), boasting (v20), and pride (4:6) over who got what from whom. These are the qualities that Paul criticized and would be considered the “wood, hay and straw” Being “fools to the wisdom of this world” (v18-19), being non-judgmental (4:3-5) and living the life of a humble servant (4:10-13, 16) are a few of the qualities that Paul considered valuable and therefore would be considered the “gold, silver and costly stone.”