(a) Except as provided by Subsection (b), an attempted waiver of a provision of this chapter is void.
(b) A written contract between an owner and a contractor for improvements to or construction of a single-family residence may provide that the payment required under § 28.002(a) be made not later than a date that occurs before the 61st day after the date the owner receives the payment request. Notwithstanding § 28.004(b), an unpaid amount under contract subject to this subsection that allows payment later than the date otherwise required under § 28.002(a) bears interest at the rate of 1-1/2 percent each month.