Rising house prices and the high number of Tauranga workers on casual contracts are making home loans less affordable, a local mortgage broker warns.

National housing affordability worsened slightly last month, the Roost home loan affordability report has revealed.

The report measured the percentage of a 30-34-year-old's after-tax pay needed to service an 80 per cent mortgage on a median-priced house.

The 30-34 bracket represented the "core" period for home-buyers.


Tauranga home-loan affordability worsened from 49.7 per cent in July this year to 54.7 per cent in August, compared with 52.9 per cent a year ago.

According to latest REINZ figures, the median house price in Tauranga is $347,500.

Tauranga's average weekly pay cheque after tax for people aged 30-34 is $737.42 - up from $722.78 in August last year.

The results come ahead of looming Reserve Bank lending restrictions on high risk mortgages - set to take effect this week.

Rapson Loans and Finance owner Chris Rapson said affordability had worsened thanks to rising property values and Tauranga residents' difficulty finding full-time employment. "Anyone who's on a casual contract, it's very difficult, even with multiple years of income evidence [because] the banks are very reluctant to advance money to those people."

Banks reneging on pre-approved loans ahead of the restrictions' deadline meant most Tauranga buyers who didn't have approval sorted before the end of August had "missed out", he said.

"If you can't take one of the pillars of the community, like a bank, on their word, then who can you take at their word?

"It was pretty poor, actually."

Ross Stanway, chief executive of Realty Services, which operates Bayleys and Eves, said the worsening in affordability roughly matched the slight increase in house prices over past months.

"There could be a correlation there that would flow through. Realistically, house prices in Tauranga and Mount Maunganui have maintained a pretty flat line but in the last five to six months, we have started to see a slight increase, so that roughly five per cent increase would probably be about it."

Nationally, housing affordability worsened from 55.4 per cent in July to 56 per cent in August after national house prices rose $5000 to $390,000.

The median weekly pay for the 30-34 age bracket is $808.54 - up from $794.80 a year ago.

Auckland was toughest for first-home buyers, where it took 92.2 per cent of an after-tax income to afford a house in South Auckland, and 102.1 per cent on the North Shore.

Affordability on the North Shore is the worst it has been in more than three years, the report found.

The cheapest place to buy was still Wanganui, with 27.7 per cent affordability. Banks have already begun tightening lending criteria to comply with the Reserve Bank's imminent "speed limit" lending restrictions, due to take effect on October 1.

Finance Minister Bill English has admitted that up to 8000 families, couples and individuals trying to get into their first home will be blocked by the new rules.

Labour finance spokesman David Parker said the number will probably be higher, with Aucklanders the hardest hit.

Mortgage brokers are working around the clock to process as many pre-approved loans as possible to reduce the number of house hunters who will miss out.

However, lending to people with deposits of less than 20 per cent has virtually "ground to a halt" as banks prepare for the deadline, Roost said.

Borrowers with larger deposits were also being offered preferentially low interest rates.

"Borrowers with more than 20 per cent equity are in a much stronger position to negotiate good deals with banks and that's where a mortgage broker can help," Roost Mortgage Brokers spokeswoman Colleen Dennehy said.

"Banks are taking much less of a one-size-fits-all approach and that means some borrowers are having to negotiate harder to get what they want."