Undercoat over gloss

Alanp

Hi, in the home where I work I’m about to start decorating one of the older rooms, it has sash windows which will require painting, the guy who fitted the new flooring said they just use undercoat over the old gloss and then gloss over that, I’ve always given the old paint a light sand before glossing, but if I can save time and effort with undercoat first, then I will, the old paint isn’t in too bad a condition nothing flaking/rotten, just a few bits of minor filling, so can undercoat first be the way to go…?

Silvertabby

I'd still rub them down first.

Who was it who said that good decorating was 80% prep and 20% dec?

Murmansk

Yes, you'd be better giving a quick sand to the current gloss paint both to clean it and to provide a "key"/increased surface area at a microscopic level for the undercoat to stick to. 

Gavin83

There are several primers which claim to be OK straight on gloss, I believe Zinsser 1-2-3 is one. However saying that were it my house I’d still give it a sanding, it’ll still give you a nicer finish and remove any doubt.

Alanp

Cheers guys, I think I’ll stick with light sand first