exterior varnish

Can I Varnish over Cuprinol Shed Treatment? My shed is painted with Cuprinol Forest Green. I repaint it once a year. I have noticed the Cuprinol around and on the door has been sort of scoured off with the rain. Could I paint varnish over it without stripping back to the wood? Thanks :)

Hi all, as the title asks, I’m looking for a good varnish for exterior hardwood, the property is located on the Norfolk coastline and is in need of some epic sanding, possibly using oxalic acid in places. It’s going to be a 3 to 4 coat job. to get it back to a reasonable coat again. I’m going...