The number of lenders tiering their mortgage interest rates according to the loan-to-valuation ratio has grown strongly over the past couple of years and is likely to continue growing.Comparison site Canstar has 18 lenders offering tiered rates on 32 owner-occupier products on its database.Those lenders include Adelaide Bank, Click Loans, Firstmac, Freedom Lend, Homeloans, Homestar Finance, iMortgage, Liberty Financial, loan.com.au Macquarie Bank, Mortgage House, MyState, Northern Inland Credit Union, Resi Mortgage Corp, State Custodians, Summerland Credit Union and Victoria Teachers Mutual Bank.Canstar said the average standard variable rate on a mortgage with an LVR of 95 per cent or more was 12 basis points higher than the average rate on a mortgage with an LVR of less than 80 per cent.The average standard variable rate on an owner-occupier mortgage with an LVR of 80 per cent is currently 4.78 per cent, while the average rate on a mortgage with an LVR of 90 per cent is 4.87 per cent and the average rate on a loan with an LVR of 95 per cent is 4.9 per cent.Canstar group executive for financial services Steve Mickenbecker said that a couple of years ago there were only "one or two" lenders tiering their mortgage rates.Mickenbecker said there were a number of other lenders that had made changes to their product set ahead of a move to tiering, adding that "we are going to see more of this." Virgin Money has announced that the mortgage it will start selling next month will have a tiered rate structure, with discounted rates based on the size of the loan and the LVR.Mickenbecker said tiered rates were one form of pricing for risk and were a response to a number of factors, including increased competition and regulatory pressure for lenders to be more prudent in their underwriting.