A hole in the cavity

bpj

neilmcl said:

Davesnave said:

Is it a log? Doesn't make much difference, as I'd change it anyway, but I have a few thousand and it doesn't look very 'loggish' to me on the full size image!

Agree, it looks more like some sort of coping stone. Possibly chose it because it matches the hole shape and size of the old flue.

I think it looks like the core removed from the flue hole. There's no pilot hole which is a bit odd, and not sure why it would be thicker than the other bricks (left the render on perhaps?) - but the mortar pattern and straight edge at the bottom look right.

Polin_ka

So I'm having someone hopefully coming to brick up the internal part of cavity and make the outside render neater. 
As the rest of the wall is insulated with mineral wool, is it necessary to fill this gap with insulation? The guy said that it's a small gap so no. I was thinking about buying some mineral/rock wool and cut a bit and fill it anyway. Do I need any special kind of wool for this job? 

stuart45

The insulation that goes into a cavity is different from what you use for your roof space. It's designed not to allow moisture through. If you don't insulate you might have some condensation form there as it will be a slightly colder spot. 
However as it's rendered outside you may well get away with it as it's only a small area.