Buy-to-let-investors are set to make steady returns over the next 13 years as rising rents and a house price recovery boost the sector, according to two reports on the property market.

Rents have already increased by 4.3% over the past 12 months and are likely to be driven further upwards by a "scarcity" of mortgage finance and a shortage of good quality properties, the Royal Institution of Chartered Surveyors (Rics) said.

Chartered surveyors predict rents will rise by 3.9% on average across the UK over the next 12 months, the Rics residential lettings survey for the second quarter of 2012 found.

In the three months to July, the number of properties coming on to the market was little changed, the study found. But demand among tenants is continuing to grow and has outpaced the change in supply since the first half of 2009, although the gap has recently narrowed, Rics said.

The study also uncovered strong regional variations. The north-west saw rents increase by the biggest margin, with a 6.9% rise, whereas surveyors in Wales reported that rents had remained at the same level over the past 12 months.

Rics global residential director, Peter Bolton King, said: "While tenant interest is still riding high, what remains to be seen is whether many are willing to meet the increasing rents being demanded by landlords.

"However, it is clear we have seen rents grow steadily right across the UK for some time. This is partly down to the problem of the scarcity of mortgage finance and the large deposits required by lenders.

"These barriers to homeownership need to be addressed alongside the shortage of new stock coming to the market."

Rents have soared in recent months as would-be buyers have remained trapped in the rental sector, unable to raise a deposit or meet lenders' toughening mortgage criteria.

Suggestions have also been made that many people are choosing to rent because of uncertainty surrounding the housing market.

The Council of Mortgage Lenders said yesterday that buy-to-let lending increased by nearly a fifth in the space of a year amid strong growth in the rental sector, although volumes remain at about a third of their peak in 2007.

Those investing in buy-to-let will make capital as well as rental returns in the long term, separate research by PricewaterhouseCoopers (PwC) suggests.

House price growth is projected to average 2% a year in real terms between 2012 and 2025, with a lack of available homes pushing up prices later in the decade once demand recovers from current subdued levels.

The rate would give a more modest return than the growth seen over the past 30 years, with increases of about 4% a year between 1984 and 2007.

Once rents are added, a landlord with a buy-to-let property could expect an average real return of 3% a year before tax but after running costs between 2012 and 2025.

According to PwC, over the next 13 years the return from a property investment is likely to be similar to that from a 50/50 mix of index-linked gilts and equities.

John Hawksworth, PwC's chief economist, said: "Given that housing returns will not be perfectly correlated with returns on equities and gilts, including housing, an investment portfolio together with these other assets could have some advantages in terms of diversifying risk.

"However, any such decisions need to be based on a detailed consideration of individual investor circumstances and needs to bear in mind that housing is a potentially risky asset as recent experience makes all too clear."