Bees don't build in lower box

I have a Warre hive.  The colony is 3 years old now.  I have harvested honey once; this year.  The colony has swarmed twice.  They have had 3 and 4 boxes for the last 2 years.  They never build in the lower box?!  For lack of any other solution I'll just keep an extra box down there at all times.  


Any ideas?

Hi,

Is the entrance at the bottom of the hive?

If so I would move the empty box to the top, then they will start using it.  Bees usually build upwards not down.

Give that a go and report back....Gary