(1) Expenditure to which this section applies is to be treated for the purposes of section 33A as expenditure on the replacement of an integral feature.

(2) This section applies to expenditure incurred by a person on an integral feature if the amount of the expenditure is more than 50% of the cost of replacing the integral feature at the time the expenditure is incurred.

(3) Subsection (4) applies where—

(a) a person incurs expenditure (“initial expenditure”) on an integral feature which is not more than 50% of the cost of replacing the integral feature at the time it is incurred, but

(b) in the period 12 months beginning with the initial expenditure being incurred the person incurs further expenditure on the integral feature.

(4) If the aggregate of—

(a) the amount of the initial expenditure and

(b) the amount (or the aggregate of the amounts) of the further expenditure,

is more than 50% of the cost of replacing the integral feature at the time the initial expenditure was incurred, this section applies to the initial expenditure and the further expenditure.

(5) Where section 33A (applies because of subsection (4), all such assessments and adjustments of assessments are to be made as are necessary to give effect to that section.