Wealth tax on house property

Dear Experts, please help.

A House property was under construction during AY 2011-12. But the Owner of the house got notice from Wealth Tax Department saying that it is subject to wealth Tax and valued it at FMV basis & Accordingly charged to Wealth Tax.

But the Assessee contended that House under construction is not subject to Wealth Tax. And to have less burden of Wealth Tax, he computed wealth Tax using Net Maintenable Rent Method.

Now I want to know whether the Assessee is right doing so?

Whether use of Net maintenable Rent Method is legal or valid?

Please kindly suggest.

Also give any notification, case law if you have