Whom does our verse discuss?
Rashi: Verse 18 reveals that it discusses Yehoyakim, who was a Rasha. Radak - after verse 12 explained the "Holech" (mentioned in verse 10), our verse explains the "Mes".
In what sense did he build his house and upper stories without Tzedek and Mishpat?
Radak: They were from theft and extortion.
Malbim: His workers were Kablanim (hired for the entire project). According to Mishpat (letter of the law), he need not pay them until they finish. According to Tzedek (beyond the letter of the law), he should have paid them first 1 . When he built the Aliyah, the house was already finished. This was without Mishpat.
Surely he means that he should have paid them according to the amount of work they did. There is no reason to pay for the entire house before it is finished! (PF)
What is the meaning of "u'Fo'alo Lo Yiten Lo"?
Radak: Fo'alo is [the value of] his work (he does not pay it). This is like "v'Es Po'al Hashem Lo Yabitu" (Yeshayah 5:12) and "Lo Salin Pe'ulas Sachir" (Vayikra 19:13).
Radak citing his father: Po'alo is his worker; he does not pay him 1 .
Malbim: Schar is based on what the employer and worker agreed on, e.g. Schar Sachir. Pe'ulah is based on what he did, even if they did not agree to a wage. Not only did he not pay Schar, for they did not fix a wage. He did not even give to him Po'alo (the value of his work)!
According to this, the verse added a word without need. It could have said Lo Yiten l'Fo'alo, or ul'Fo'alo Lo Yiten! In any case, this entire phrase repeats the previous matter. Radak (7:4, and throughout Nach) says that verses do so to strengthen the matter. (PF)