Shares in the FTSE 100-listed firm fell 6% after Wolseley said like-for-like revenue growth dropped to 1% in recent weeks, down from 2.8% in its third quarter.
The building supplies group said it had “committed to further restructuring” as part of an overhaul announced in March that will see 14 branches closed and around 300 jobs axed.
Its bill for the restructure will increase to around £20 million this year, up from £15 million previously.
The additional revamp efforts are not impacting further on branches or jobs, although there are fears of more cuts to its 6,200-strong UK workforce as it carries out a root-and-branch review of its British business.
It said it aims to complete the UK review by August.