On 23 Feb 2005 02:04:26 -0800, (jacob)
wrote:

No need to seal the back - just paint the visible bits. One universal
rule of trad joinery is that nothing unseen is ever painted - its
cheaper and allows the wood to "breathe".

Hi,

IMVHO there is some value in treating and protecting the hidden end
grain of outdoor joinery, so it's less likely to suck up water and rot
spores into the timber at the first opportunity.

OK in an ideal world the timber would be finest quality and painted
every year without fail, but that doesn't always happen, and doesn't
help once problems start.

cheers,
Pete.