17th Century Timber framed house - breathability

[Zebra579]

Hi,

I have a 16th Century timber framed house. It has been previously rendered with a cement render, onto expanded metal lath attached directly to the frame.

Clearly, a timber frame ought to be ventilated, and this cement render does not allow the frame to breathe. Moreover, where the cement has cracked, this has been letting water in and not letting it evaporate back out, causing local rot, which I have now cut out.

I am loathe to remove the render throughout, as it is offering considerable structural support to the frame. But I am looking for a way of allowing an air flow around the frame. I am wondering whether I could, for example, drill lots of holes in the render, counter batten and re-render over the top in lime. Or have airbricks or vents in the outer render. Would I use a breathable membrane? In which case where?

Does anybody have any expertise in the area of old buildings, and can anyone advise on how I could allow a timber framed house to breathe, through the cement render, and allow an air flow around the frame?

Many thanks

 

[freddiemercurystwin]

I am loathe to remove the render throughout, as it is offering considerable structural support to the frame

Render does not offer structural support.

 

[thatbloke]

It will do if the frame has rotted to compost.

I have replied in your other post zebra.

 

[freddiemercurystwin]

So render is supporting the walls then?

 

[thatbloke]

possibly freddy, the front of my cottage is pretty much the same scenario , the timber frame had been chopped to put in windows in the 40's/50's and wasnt done properly, it should have had an oak framework build around the windows supported on the sole plate, what they did was bolt a lintel to the studs either side then put the windows in in a 2x4 soft wood heath robinson frame work , they then rendered and plastered in cement.
When the sole plate and soft wood eventually and inevitably rotted the only thing supporting the wall plate is the cement render, the only studs that were left after the window insertion are on sky hooks.

This doesn't mean removal of the render will cause collapse (every situation will differ and usually the corner posts and bay posts are way more substantial than the studs) but it will move considerably and one has to support the frame above the render when removing it to prevent further damage from occurring.

 

[Zebra579]

So render is supporting the walls then?

Yeah, I think so. Where there is rot in the frame, I think its the expanded metal, stapled to the studs, with inch thick cement render surrounding the building on four sides, I think is holding the building in shape and keeping it from warping...

Thanks thatbloke, noted your other reply.