Can you paint over gloss without sanding it first

You can, but only if you replace the sanding with something that does the same job: an adhesion primer, or a liquid deglosser. Paint applied straight onto unsanded gloss will look perfect for a few weeks and then lift off in sheets the first time something knocks it.

Sanding is not a ritual. It is one of three ways to solve a specific problem, and there are situations, particularly in older Wellington houses, where sanding is the worst of the three.

Why does gloss reject paint?

Paint holds on in two ways. Mechanically, it keys into microscopic texture in the surface. Chemically, it bonds to what is underneath. A cured gloss enamel offers close to nothing on either count: it is hard, closed and slick by design, which is exactly why it gets used on doors and skirtings that are handled every day.

So a new coat sits on top like water on a waxed car. It dries, it looks right, and then it fails at the join. The tell is peeling in sheets that come away clean, with the gloss underneath still shiny and undamaged. That is adhesion failure, not a paint quality issue, and it happens with expensive paint just as readily as cheap paint.

What are the three ways to get grip?

Method	What you do	Best for	Watch out for
Abrade	sand to a uniform dull finish with the abrasive grade the paint's data sheet asks for, then remove all dust	most sound gloss on trim, doors and joinery	dust everywhere, and not suitable dry on paint from the 1980s or earlier
Deglosser	wipe on a liquid deglosser, or wash with sugar soap and abrade lightly	intricate mouldings and spindles, and rooms where dust must be controlled	the surface has to be genuinely clean first, and recoat windows are short
Adhesion primer	clean thoroughly, then one coat of a bonding primer	slick surfaces you cannot abrade evenly, and mixed substrates	costs more, and still fails over grease

All three work. The mistake is doing none of them, or doing one badly and assuming it counts.

Sanding by hand is also faster than people fear. A room's worth of skirting, architraves and one door is roughly an hour with a sanding sponge, and a sponge follows a moulding profile where flat paper cannot.

What is the step everyone skips?

Washing. Old enamel joinery in a kitchen, a hallway or around light switches carries cooking grease, hand oils and years of airborne residue. Sand over that and you drive the contamination into the scratches you have just made. Prime over it and the primer bonds to the grease rather than to the paint.

Wash with sugar soap or a proprietary pre-paint cleaner, rinse, and let it dry. Do it before you sand, not after. It takes twenty minutes and it makes more difference to whether the job lasts than any choice of primer.

Does it matter what the existing gloss is?

Yes, and on Wellington villas and bungalows it usually turns out to be old solvent-based enamel. That matters twice.

First, aged oil enamel goes brittle and yellow, and it can be chalky under the shine. Waterborne enamel over prepared oil enamel is entirely normal and works well, but the preparation has to be right: clean, dulled, and primed with something intended to bridge the two systems.

Second, waterborne enamels stay soft for longer than they look. They are touch-dry in hours but take considerably longer to reach full hardness, and in a cold Wellington winter that period stretches out further. Door edges and window stops closed too early will stick and tear, which people blame on the paint when the real problem is the calendar. Leave doors ajar and put a strip of clean paper between the stop and the door for the first few days.

When is not sanding actually the better choice?

Any house built in the 1980s or earlier. A large share of Wellington's villas and bungalows fall into that period, their older paint layers can contain lead, and a test is the only way to know. Dry sanding lead paint produces fine dust that settles into carpet, ends up on hands, and does not vacuum out easily.

In that situation the deglosser or bonding primer route is not a shortcut, it is the correct method. If you must abrade, wet-sand so the dust binds into a slurry, catch it on sheeting, and dispose of it properly. Do not run an orbital sander over painted villa joinery on the assumption it will be fine.

The other case is intricate work. Deep mouldings, carved detail, balusters and pressed panel doors are close to impossible to abrade evenly, and a bonding primer gives a more uniform result than an hour of frustrated scuffing in the corners.

How do you check before doing the whole house?

Do one small area. Prepare a patch about the size of your hand using whichever method you have chosen, apply the topcoat, and leave it a full week, longer in winter. Then cross-hatch it with a blade, press packing tape hard over it, and pull sharply. If the paint stays, your preparation works on this surface. If it lifts, you have learned that on a patch instead of on a hallway.

A week feels slow. Redoing every door in the house is slower.

Is this a job you can do yourself?

Repainting glossy trim is one of the better DIY jobs. The areas are small, materials are inexpensive, access is from the floor, and mistakes are recoverable. If you want somewhere to start, start here rather than on a ceiling.

Bring someone in when the house was built in the 1980s or earlier and you would rather not manage lead dust yourself, when there is enough joinery that you want a sprayed finish rather than a brushed one, or when the existing coating is failing for a reason nobody has identified. If the current gloss is already peeling off the timber, adding a coat over it solves nothing. That is a stripping job, and it belongs with the rest of your interior painting rather than being treated as a quick fix.

If you want the joinery done properly and you would rather not spend three weekends on it, get in touch for a quote.