How is the Zakat calculated for a house that was built over ten years, and no Zakat was paid on its construction expenses during that period, and it began to be rented out this year?

Zakat is obligatory on money spent on building a house if the conditions for Zakat are met: namely, reaching the nisab (the value of 85 grams of gold or 595 grams of silver) and the passing of a full lunar year (hawl) before it was spent on construction. The amount due is a quarter of a tenth (2.5%). However, if the money did not reach the nisab, or a full year did not pass on it before construction, then there is no Zakat on it. After the house is rented out, Zakat becomes obligatory on the rent if it reaches the nisab and a full year passes on it.