Several one-off costs saw interim pre-tax profit decline at residential company Grainger.The FTSE 250 group posted a pre-tax profit of £9.1m for the six months to 31 March, down from £49.8m in 2014 as the company fronted a host of exceptional costs, including an £18.2m impairment related to the failed sale of a home reversion portfolio subsidiary.Grainger was also hit by a 312.7m reduction in valuation gains as well as a 313.9m negative movement on derivatives.However, the group said that excluding the three one-off charges, its recurring pre-tax profit climbed 13.4%, boosted by a contribution from the Macaulay Walk development and strong sales of vacant space.Profit from sales rose 5.4% year-on-year to £45.1m, while net rents declined 2.6% to £19m and gross fee income fell 17.6% to £4.2m."In the first six months of our financial year we have continued to see strong margins on sales of our assets and encouraging levels of activity in both the transactional and rental markets," said group chief executive Andrew Cunningham."Our portfolios have again outperformed the general market for the fifth year, demonstrating the quality of our assets and our management capabilities."Grainger said it was encouraged by its sales pipeline, which rose 15.3% to £151m in the period from 31 March to 8 may.Analyst at Numis said the results were in line with estimates and that the growth in the group's pipeline was encouraging."In our view as Grainger's market rented portfolio grows and net rents benefit, it has the potential to increase shareholder distributions and achieve a valuation more in line with wider commercial property sector," they said in a note.Grainger shares were up 0.28% to 214.00p at 10:56 on Thursday.