Do I need primer and then undercoat before i use a gloss paint?

If you are painting bare wood? first treat the knotts then use a primer/undercoat 2 coats is best then top coat of gloss. if painting wood that is already painted you can just rubb it down a little then gloss if you are using a good gloss but of course one coat of undercoat would be best first.

If the wood is bare you will need to use a knotting solution on all knots, an acrylic primer will be fine, then undercoat and lastly a gloss. If wood has already been painted, then you will only need an undercoat and a gloss coat. If painting outside, it would be ideal to apply 2 coats of gloss due to weather conditions. You should also lightly sand down between coats. The reason they suggest not using an acrylic primer with oil based paint is because the oil based paint takes longer to dry than acrylic which could cause cracking of top coat, but if acrylic is dry properly it will be fine, I've never had a problem.

We tend to use the Dulux Weathershield System. On previously painted timber we use x2 undercoats and x1 gloss coat. On new timber, we knot, sand and fill, and then x2 undercoats, x1 glosss. Chris Foster.

Definitely use a primer / undercoat Think of it, as painting your car the topcoat is the nice shiny finish but to get that there are several layers of paint under it to help attain that finish. There are many primer undercoat paints on the market so you need only use two types of paint rather than a Primer - Undercoat - Gloss solution You should also use a Knotting solution before painting Do not use an acrylic paint with Oil based Gloss

SBS Ltd has pretty much summed up the process that you should carry out.It can vary slightly depending on the current woodwork finish but all i can add is to make sure you rub down between coats with suitable grade sandpaper reducing down to a 240 grit paper before glossing,hope that helps,Gary