(a) Construction plans. Except as provided in Secs. 4211.11(b) and 4211.21(b), a plan that primarily covers employees in the building and construction industry shall use the presumptive method for allocating unfunded vested benefits.
(b) Section 404(c) plans. A plan described in section 404(c) of the Code or a continuation of such a plan shall allocate unfunded vested benefits under the rolling-5 method unless the plan, by amendment, adopts an alternative method or modification.