Loan-to-value, usually shortened to LTV, compares the mortgage balance with the property's assessed value. As the balance is repaid or the property's value changes, the LTV can change too. This may affect which products and lenders are available.
An online estimate or estate-agent appraisal is not necessarily the value a mortgage lender will use. The new lender may arrange an automated, remote or physical valuation and apply its own criteria. If the valuation is lower than expected, the LTV and available options may change.
Having equity in a property does not by itself demonstrate that additional borrowing is affordable or suitable. Income, expenditure, credit commitments, property type, mortgage term and lender criteria remain important.