We have replaced single glazed crittall windows that were traditionally fixed onto timber subframes with aluminium double glazed windows in our 1940s cottage style home. As the original timber subframes were deeper there is now a gap on the window surround walls and also the timber window boards. What plaster methods should be used to fill these gaps internally. From what i understand, bonding and finish may act as a sponge and cause dampness around the windows in the future. Will render and finish be the right combination ? Or is there a better method ? I understand that old methods of plastering used lime which made the plaster more porous and so moister could therefore escape and not get trapped. Also how do we repair and blend in the original window boards without replacing them which will only cause more damage to the plaster. Should we splice timber in and then use a 'd' section timber trim to cover the gaps ? Followed by stain where window board is stained and paint where painted ?
