plaster on wood

Hi,DIY PLasterer here.
i am dropping the height of my door frame down about 5cm.
i am gonna do this the easy way by screwing some wood from underneath into the top of the existing door frame.

question is. When i skim the wall. Do i just PVA the wood to get the plaster to stick to it when i skim or will i have to put some mesh or scrim on the wood ?.
Paul.

I'm only a DIY plasterer too but plastering over wood is probably a mistake.

Plaster is a hard, brittle material whereas wood will expand and contract with changes in temperature and humidity. Result - one day the plaster will crack.

My advice would be to face the wood with a layer of plasterboard and skim that. It might also help to feather the edges of the existing plaster so that you can scrim the join, before skimming.

I prefer screws to nails to fix plasterboard as nails tend to pop when the skim doesn't adhere properly to the nail heads.

Make sure you use proper rustless plasterboard screws with trumpet type heads.

Exactly what Ratter said above.