(ShareCast News) - RBC Capital Markets downgraded Barratt Developments and Taylor Wimpey as it tempered its view on housebuilders ahead of a potential interest rate rise.The Canadian broker maintained that the structural demand drivers and land-buying trends are positive, and that the sector has become more disciplined regarding capital allocation. However, it said margin expansion, cash-flow generation and potential shareholder returns were now reflected in sector valuations.It cut Taylor Wimpey to 'outperform' from 'top pick', saying the stock has now re-rated considerably, but lifted the price target to 220p from 190p.RBC said Wimpey has been the strongest performer in the sector, outperforming by 10% year-to-date."We see 2015 as the end of its investment programme, with Taylor Wimpey moving to land replacement mode. We believe that this has been a catalyst for the shares, driving outperformance."The bank downgraded its stance on Barratt Developments to 'sector perform' from 'outperform' but lifted the price target to 680p from 575p.It said Barratt has successfully shifted from being a volume housebuilder and it is now focused on the expansion of return on capital employed, with capital discipline supported by cash returns to shareholders."We believe that the improved mix is now largely being reflected in the share price," the analysts said.At 1018 BST, Taylor Wimpey shares were down 2.3% at 189.20p while Barratt was 2.2% weaker at 597p.