say you borrow 90% of your market value RM300k in year2010, the loan amount = RM270k

come yr2013, market value(#) become RM500k, you can borrow 90%(*) of the market value = RM450k minus the outstanding of your previous loan. If you still owe RM250k from the previous loan then you can borrow RM450k minus RM250k = RM200k

(#) market value is determined by the bank's valuer
(*) margin of finance is different for every bank
- Top up only allowed from the same borrowing bank because the property have been charged to the bank
- you'll need to pay for the legal fees, stamp duty etc based on the new loan amount
- the new loan tenure can be different with the original loan because it is a separate facility
- approval still depends on your credit eligibility
so on