Cavity wall insulation

[clivejo]

There are no weeps, holes or vents.  The outside is pebble dashed and there is no distinction between the solid wall and cavity walls on the outside.

[rhys]

 This sounds like a very unusual construction. Was the upperflor built at a later date?

[clivejo]

The upper floor was solid construction too, but it was knocked down to first floor level.  A concrete rim was put around it and then cavity built on top.  I remember my dad saying he should have knocked it all down and started from scratch, but the people who knew better wouldn't let him.  He wanted to have a wee accident with the digger bucket!   

[rhys]

OK that makes sense, but the earlier comments about weep hole and cavity trays at the bottom of the newer wall, are important. The render is stoping external rain getting into the cavity, as long as its in good condition, but condensation from the house may well be getting into the wall, where is it going to? Perhaps opening up a small area would be worth while just to make sure nothing is getting too damp at the bottom of the cavity?

[clivejo]

I'm thinking of getting the pebble dashed render painted this summer (well the north/west walls as a test),  as an extra precaution to keep the rain out.  The bottom of the wall seems dry to me its the top that gets cold and then condensation appears.  I've been keeping the heat up this winter via the WBS as a kind of test. But these cold mornings I'm seeing damp along the top 2-4 foot.