Emulsion over undercoat?

[Bromley86]

We've just sanded down the walls in the dining room. I got a bit carried away leveling the edge of the vertical pipe boxing in the corner, so parts of the batten and the edge of the ply sheet are exposed. The ply face is still covered and the other edge of the ply is in the corner, so no problems there.

The boxing had previously been painted with the same emulsion as the rest of the room and blended in fine, so we'd like to do that again.

Obviously, I'd prefer to just emulsion without undercoat, but is it necessary to use undercoat on the batten and ply edge first? Will that create problems when we emulsion over it? Do I need to sand off all of the old emulsion first?

Thanks.

[Peter]

In my experience, if the area is exposed, in the sense that it is often touched, then prime it. If its out of the way, emulsion should be fine. Emulsion works on most surfaces but is useless when a lot of contact is made, witness areas around light switches etc.