NEW YORK ( TheStreet) -- Homebuilder stocks lost ground Friday to a greater extent than the broader equities markets, but the poor performance of building-materials sales within the disappointing retail report might not be the only reason for the selloff. It's been a two-day span of schizophrenic trading in homebuilder stocks. On Thursday, the sector as a whole spiked 5%. It wasn't just Thursday's broad-based rally that lifted homebuilders, either -- just as it isn't wise Friday to read too much into whatever weakness was demonstrated by the building-material and garden-supply sub-category of the retail-sales metric. Standard & Poor's released a report on Thursday about homebuilders, arguing that the industry has bottomed out and that it's time for the surviving builders to acquire new land and gain market share. The S&P report garnered some attention from investors waiting for signals that major homebuilders such as D.R. Horton ( DHI) and Toll Brothers ( TOL) will soon move out of a defensive posture and become aggressive with their strategies. On Wednesday, Stifel Nicolaus removed its last remaining sell recommendations on homebuilder stocks -- though it still doesn't have a single buy rating. The firm lifted D.R. Horton, MDC Holdings ( MDC) and Pulte Group ( PHM) to hold. In the market selloff over the past month, the three stocks had fallen below book value, and Stifel Nicolaus said its call was based purely on valuation. Senate Majority Leader Harry Reid (D-Nev.) also announced on Thursday plans to extend the homebuyer tax credit until the end of the summer, but the plan is primarily to make sure homebuyers who did make purchases before the April 30 deadline have extra time for the mortgage paperwork leading up to closing. On Friday, the Commerce Department reported that retail sales in May tumbled an unexpected 1.2%, the first decline since September 2009. One striking data point in the report was the 9.3% plunge in sales at building-material and garden-supply stores.