Finish on painted, custom bathroom vanity?

Question

As part of a bathroom remodel, I've built a custom vanity. For the exterior (face frame, doors, drawer faces) I've painted it with a satin finish latex paint (4-5 coats). The interior is bare wood with polyurethane.

Our contractor is recommending I spray this (the painted vanity) with lacquer, I would have thought paint alone would be a fine finish. Am I wrong?

Should I finish the painted wood with lacquer (or really any film forming finish)?

EDIT for Additional Details:

This is the vanity for the master bath (adult use only). The carcass is made from 3/4" plywood (from a big box store, so poplar layers with a Sandee veneer), the face frame is made from solid poplar. Doors are 1/4" baltic birch panel with poplar frame, drawer fronts are solid poplar. Paint is Sherwin William Duration for the additives to resist moisture issues. The top will be quartz, I would be shocked if there's any standing water (horizontal) on the vanity at all. It's boxed on both sides by a knee wall and a full wall and it's a floating vanity, so there's no risk of water pooling on the ground around it.

Answer 1

As we have no details of the construction, materials, potential for splashing and for water to sit on horizontal surface, and the lifespan you hope for/expect from the project, we can't really advise for your specific case. But the below should help clarify some of the relevant points to help inform your decision.

I would have thought paint alone would be a fine finish. Am I wrong?

Nope.

Although by no means an exact analogy a good starting point is thinking about what's likely used on the skirting in your bathroom, or in any typical modern bathroom in fact..... then think about the walls. Yup, "latex paint".

What we call latex paint¹, although they're all pretty similar, is by no means one, homogenous product however. Obviously there are interior and exterior grades to start with, but even within those two categories they can and do vary — hence the differences in finish, wear resistance, lifespan and so forth².

Should I finish the painted wood with lacquer (or really any film forming finish)?

If you want greater waterproofing than the paint will (typically) provide by itself, yes. Most clear overcoats will also give you greater scratch resistance which could prove a decent bonus in the long term.

The thing about "latex paint" is that while they are 'waterproof' in the sense that they're not damaged by water, they are not water-blocking. This is actually one of the key selling points of the paint type as exterior paints, they allow water that does find its way into the wood to get back out again, which is good for both the wood itself and the paint film in an exterior context.

Your contractor is probably thinking conservatively (no bad thing) and wants your project to have the best chance of enduring in good shape. But whether added protection is truly necessary is a judgment call as much as anything.

• The quality of the paint you've used is one of the two key factors.
• The material type(s) are as important or more important.
• The construction details matter.
• Your use-case is definitely a factor³.

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¹ Note: does not contain latex LOL

² Somewhat reflected in differences in cost, although never discount the unfortunate reality of name-brand premiums.

³ I'd want great built-in reassurance in a vanity intended for general family use than in one that only the adults will use.