The largest housing price decline ever, the Great Recession, had a 34% decline from 2005-2009, when it ended and housing prices began to rise again. (Case Schiller Price Index) In the 7 years from 2009 to 2016, housing prices reached the pre-recession peak.
Prices will probably drop in a recession, but just like we haven't seen stock prices drop like the Great Depression, it is highly unlikely that we see drops again in housing like the Great Depression-especially given the factors that lead to that drop are not currently present in the market.