Per St John Chrysostom:http://www.newadvent.org/fathers/220109.htm
5. “If any man build upon this foundation, gold, silver, costly stones, wood, hay, stubble.” For after the faith there is need of edification: and therefore he says elsewhere, “Edify one another with these words.” perhaps 1 Thessalonians 5:11; 4:5 For both the artificer and the learner contribute to the edifying. Wherefore he says, “But let every man take heed how he builds thereon.” 1 Corinthians 3:10 But if faith had been the subject of these sayings, the thing affirmed is not reasonable. For in the faith all ought to be equal, since “there is but one faith;” Ephesians 4:5 but in goodness of life it is not possible that all should be the same. Because the faith is not in one case less, in another more excellent, but the same in all those who truly believe. But in life there is room for some to be more diligent, others more slothful; some stricter, and others more ordinary; that some should have done well in greater things, others in less; that the errors of some should have been more grievous, of others less notable. On this account he says, “Gold, silver, costly stones, wood, hay, stubble—every man's work shall be made manifest:”— his conduct; that is what he speaks of here:— “If any man's work abide which he built thereupon, he shall receive a reward; if any man's work shall be burned, he shall suffer loss.” Whereas, if the saying related to disciples and teachers, he ought not to “suffer loss” for disciples refusing to hear. And therefore he says, “Every man shall receive his own reward according to his own labor” not according to the result, but according to “the labor.” For what if the hearers gave no heed? Wherefore this passage also proves that the saying is about actions.
Now his meaning is this: If any man have an ill life with a right faith, his faith shall not shelter him from punishment, his work being burnt up. The phrase, “shall be burned up,” means, “shall not endure the violence of the fire.” But just as if a man having golden armor on were to pass through a river of fire, he comes from crossing it all the brighter; but if he were to pass through it with hay, so far from profiting, he destroys himself besides; so also is the case in regard of men's works. For he does not say this as if he were discoursing of material things being burnt up, but with a view of making their fear more intense, and of showing how naked of all defence he is who abides in wickedness. Wherefore he said, “He shall suffer loss:” lo, here is one punishment: “but he himself shall be saved, but so as by fire;” lo, again, here is a second. And his meaning is, He himself shall not perish in the same way as his works, passing into nought, but he shall abide in the fire.
6. He calls it, however, “Salvation,” you will say; why, that is the cause of his adding, “so as by fire:” since we also used to say, “It is preserved in the fire,” when we speak of those substances which do not immediately burn up and become ashes. For do not at sound of the word fire imagine that those who are burning pass into annihilation. And though he call such punishment Salvation, be not astonished. For his custom is in things which have an ill sound to use fair expressions, and in good things the contrary. For example, the word “Captivity” seems to be the name of an evil thing, but Paul has applied it in a good sense, when he says, “Bringing into captivity every thought to the obedience of Christ.” 2 Corinthians 10:5 And again, to an evil thing he has applied a good word, saying, “Sin reigned,” Romans 5:21 here surely the term “reigning” is rather of auspicious sound. And so here in saying, “he shall be saved,” he has but darkly hinted at the intensity of the penalty: as if he had said, “But himself shall remain forever in punishment.” He then makes an inference, saying,