Input On GST

yes u can . . . 

u are constructing the shed so u can take input tax credit 

but 

if a customer purchased the same so he cant take itc as immovable property for the same persn 

No , Input  tax credit  not avaiable  as per section 17 sub section 5(d)  of the CGST act  2017 goods  received  by taxable person for construction of an immovable property used  in the course of furhterance of Busniess .

Fruther  it is mentioned in the explanation - for the clause (d) the expression contruction  includes Re- contrucation , renovation , additions or alterations or repairs  to the said immvoable property .

please confirm  with others also .

No ITC is available, since goods or services or both received by a taxable person for construction of an immovable property (other than plant or machinery) on his own account including when such goods or services or both are used in the course or furtherance of business.

Thus no ITC on goods can be taken.