teignbee,
No, solid floors are not that bad. They have their uses. Can't think of many off-hand, but I'm sure they do....
Seriously, you could make them much more ventilated by cutting/drilling holes in them and covering with mesh. Maybe not ideal, but as long as the boards are not totally cut through, it could be an option before saving up for OMFs, or getting around to making some, or awaiting the winter sales or....whatever.
They were used without too many problems(?) for about a hundred years, or more, before OMFs became an option. Not seen too many WBCs with OMFs. But my WBCs didn't have a condensation problem either!
I had condensation problems in Nationals when I started and also lost a colony because of too much top ventilation (I thought at the time). I just found OMFs so much less of a problem - like I did away with top ventilation and it remained dry in the hives. So they are almost universal now on my hives.
Oh yes, my bait hives are always with solid floors.
Even my nucs are generally on part-mesh floors - but they are deep, and do have 'nuc supers' on too!
Regards, RAB