The Verroa mite was first found in the UK in 1992 and soon spread throughout the
Country. It devastated the honeybee population and lots of bee keepers were forced to give up.
It is well documented that Verroa mites drop off the bees and some will eventually reach the floor. If this is of the solid type the mites can easier climb back onto the comb, but given a mesh floor they fall through to be eaten by ants and the like. Open mesh floors are simply a floorboard where the solid wooden section is replaced with a sheet of wire mesh. It is documented that as many as 40-60% of the mites can be removed from the hive using this method. This method is promoted in the latest UK Ministry of Agriculture leaflet titled ‘Managing Verroa’ where they emphasis this is a method which can be used throughout the year.
An example of a bee hive floor construction
Kindly reproduced from https://website.lineone.net/~dave.cushman/natomf.html
Open Mesh Floor to suit National Hive, in America they call this a "Screened Bottom Board"
The Grain should run along the longest dimension of any part.
The under rim should be made first, gluing and screwing the corners.
The mesh should be stapled in each corner and along the exposed front edge,
then the upper rim parts are added using 38 mm Csk twin thread woodscrews through the bottom rim into the top parts so that the heads of the countersunk screws are underneath.
An entrance block of 421 mm x 21 mm x 21 mm (Thorne's size) will suit the 22 mm timber version or if 21 mm stock is used the entrance block needs planning down to 20 mm square to suit.
The version as drawn above is simple to construct. If petroleum jelly is used on the upper surface of the top rim and linseed oil is used on the other wooden parts, (take care that the linseed oil does not block any of the holes in the mesh panel, as it will dry to a rubbery consistency).