The tax credit was only a small reason or as they stated in the article partly due for the increase in spending. The bottom line is that home improvement spending increased 3.5% in 2010 from 2009.
Fitch Ratings expects home improvement spending to increase 3.5% in 2010 over 2009 levels, partly due to an influx of home sales incentivized by the first-time homebuyer tax credit:
Existing home sales are an important driver of home improvement spending, as owner occupants will often remodel existing home purchases and renovate homes before selling.