Plaster and lath repair

[johnnymac1]

I live in a 1930's bungalow that has a roof overhang above the front door, which forms a small external porch. A patch of the rendering on the 'ceiling' of this porch has fallen down, and exposed a plaster and lath construction, part of which has obviously rotted. I don't yet know the extent of the rot, and whether I can patch it with mesh or need to replace it entirely with plasterboard - the whole area probably isn't more than about a square yard. Anyway, what I'm uncertain about is how to finish the surface once I've repaired it. As it's an external area, although under cover, can I just use ordinary ceiling plaster, or do I need something else? Also does the finish depend on the type of repair ie mesh or plasterboard? Any advice would be gratefully received - as would any tips generally about doing the repair itself, before I start hacking away. Thanks very much.

[demoman]

Hi Johnnymac1 the first thing i would be concern with is why the laths had become rotten. There could be a roof leak that need sorting out before you think about any cosmetic work. I am finding it hard to picture the location of the rotten laths. It sounds like your talking about the eaves of the roof. I would recommend screwing up a finished moisture resistant board. British Gypsum do a 6mm and 10mm glasroc board it is ideal for exposed areas and can be painted. just countersink the screw holes and fill them. I dry lined my bathroom with them as i couldnt be bothed skimming the walls and 6 years later they are still perfect.