The following provisions shall have effect in substitution for the provisions of section ninety of the Lands Clauses Consolidation (Scotland) Act, 1845, that is to say, no person shall be required to sell a part only of any house, building or manufactory, or of a park or garden belonging to a house, if he is willing and able to sell the whole of the house, building, manufactory, park or garden, unless the tribunal by whom the compensation is to be assessed determines that, in the case of a house, building or manufactory, such part as is proposed to be taken can be taken without material detriment to the house, building or manufactory, or, in the case of a park or garden, that such part as aforesaid can be taken without seriously affecting the amenity or convenience of the house, and, if the tribunal so determines, the tribunal shall award compensation in respect of any loss due to the severance of the part so proposed to be taken, in addition to the value of that part, and thereupon the party interested shall be required to sell to the acquiring authority that part of the house, building, manufactory, park or garden.