Where my washing machine drains out in my basement floor I have an occasional backup.. I have snaked it several times and have even had a plummer come out and snake it... and every time we find nothing.. Any ideas as to why this is occurring.. Appreciate the help..

Sometimes this is caused by too much soap causing a foam that restricts the water flow as it tries to drain. Are you getting suds in the overflow? And [watch this tom] sometimes the pipe is not long enough before it reaches the trap. The code calls for a minimum of 18" drop up to 42 inches. Typically though the pipe is long enough and all you got to do it cut back on the soap.