Each and every co-owner/joint owners are entitled to claim deduction of interest u/s 24(b) payable against capital borrowed . Each co-owner/joint owner can claim deduction upto a maximum of Rs. 1.5 Lakh per annum, if loan is acquired for construction/acquisition of house property or Rs. 30 K per annum, if loan is acquired for repair of house property.
If the house property is let-out, then the deduction aforementioned is without limit, subject of course, limited to the amount to be paid to the bank.
Thus in the present context, both Husband and wife can claim the deduction of interest paid/payable against the loan availed, since both are entitled to such deduction. However, if the wife cannot avail deduction for certain reasons (assuming that she does not have any taxable income earned during the year), her husband can claim his share of deduction subject to the limits as mentioned above.
To make the above simple, consider the following example:
Interest Payable/Paid during the previous year Rs.2,00,000
Entitlement of deduction to both Husband and Wife Rs.1,00,000
(Having equal share in property)
As per your query, if wife cannot claim the deduction, then:
Her husband can claim Rs. 1,50,000 (if not let-out)
or Rs. 2,00,000 (if let-out)
P.S.: In addition to interest deduction, they are entitled to deduciton u/s 80 C of principal repaid during the previous year.