Unless you mean something different by single walled hives, most hives in
the US are single walled, painted on the outside.  Unpainted hives may be
more common in England where cedar (weather resistant wood is used).  Most
of ours, with the exception of Rossman's cypress boxes and a few speciality
hives, are constructed from softwoods- pine or fir.  Without paint, they'd
quickly weather and warp.  So, with or without screens, painted boxes are
used by the millions on this side of the pond.

I've also seen lots of unpainted hives in poor, tropical countries.  I
suspect that 1) their slab wood may come from more rot-resistant wood, and
2) its viewed as an additional expense.

Jerry

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