Cavity wall insulation

[diyholiday]

We have a 1930's house with an extension in middle of rear.
Extension has cavity wall insulation. Main house doesn't. Had guy in to see about grant for filling cavity. He drilled a hole and measured the cavity but he says the cavity is too small to fill
Is this the case? Can cavities be too small? We have dormer windows at the front, and it is these walls to the front that seem uninsulated.
What, if anything can I insulate these with please? Or should I be looking at internal insulation

 

[stuart45]

Most CWI companies won't fill a cavity of less than 40mm. There were quite a few houses built in the 20's and 30's with stretcher bond but solid walls. These were sometimes mistaken for cavity walls and insulated, with problems of damp following. Nowadays they drill into the walls and put a camera in to be sure they ae suitable for filling.
It might be that internal insulation is your only option.

 

[diyholiday]

Thanks Stuart45,
I have taken off a windowsill in the kitchen and noticed the cavity being rather small, BUT it is full or rubble! May need to empty that incase of damp?
Smaller rooms may be in order then

 

[stuart45]

You might find that the cavity is filled in most places. It could have been built as a solid wall in stretcher bond rather than a cavity wall. Although there should only be a 10mm gap the bricklayers at that time would often increase this to about 25mm to make it easier to build the inside skin. As it was a solid wall they threw mortar and brick rubble in to fill the gap.