Hi there, I want to paint over stained exterior wooden bifold doors but unsure as to which products to use. I’ve been told that just painting over it is not advisable. Many thanks

Assuming the stained timber is clean, dry, sound and prepared as detailed in the technical data sheet you could consider Zinsser Cover Stain followed by Zinsser AllCoat Exterior (Water Based).

This can be mixed to many RAL, NCS or BS colours in a matt, satin or gloss finish.

We would recommend to test on a small area for compatibility and adhesion prior to full application.