How to repaint window sill & mailbox?

aaronkhoocy

Hi there! I'm looking for advice on repainting the window sill and the top of my mailbox.

Some questions in my mind

1. Assuming I need to sand them first, do i need to strip the existing layer of paint out completely?

2. To strip the paint, a combination of sand paper and paint scrapper will do the trick?

3. Does it require a primer? A colour that closely resembles the current colour?

4. A regular exterior paint would work?

5. Does it require a top coat?

Thanks!

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Comments

MitchellMc

Great questions @aaronkhoocy, and you’re definitely thinking about the right things before diving in. From their appearance, these are very likely glazed tiles or thin bricks with a glazed coating. The darker areas are the remaining glaze, while the lighter patches are where the glaze has worn away and you’re seeing the raw material underneath.

This is where it gets tricky. Glazed surfaces are non-porous, which means paints generally can’t bond to them properly outdoors. Interior tile paints exist, but they are not designed to handle UV exposure, temperature changes, or moisture long term, so they tend to fail outside. Paving paints are also not suitable unless the surface is porous. A simple test is to drop some water on the surface. If it beads up and doesn’t soak in, which is almost always the case with glazing, then paint will not adhere reliably.

In terms of your specific questions, sanding and scraping alone won’t be enough unless you completely remove the glaze back to a porous substrate. Glaze is extremely hard, much harder than normal paint, so standard sandpaper won’t cut through it effectively. You’d be looking at aggressive grinding, and even then, getting into corners and edges evenly is difficult, so the end result is often patchy. Because of that, stripping the surface back far enough to make paint viable is usually not practical.

Primers, exterior paints, and top coats won’t solve the underlying adhesion problem if the surface remains glazed. Even the best primer will eventually let go if it’s applied over a non-porous exterior surface like this.

Realistically, there isn’t a reliable paint system for exterior glazed tiles. If the appearance is bothering you, one option is to leave them unpainted and accept the natural variation, or possibly try a masonry or brick sealer to even out the look slightly. Even then, adhesion can still be hit and miss on glazed areas, so expectations need to be realistic.

I know that’s probably not the answer you were hoping for, but it’s better to know upfront than put in the effort only to have the coating peel later.

Please let me know if you have any questions.

Mitchell

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