Maz
Guru
Thanks.Your house is cavity - you tell by looking at the stretcher bond to the gable end wall in the loft (not the shared wall with the other semi). The age of the property may mean that your wall ties are on the way out. The first sign will be horizontal cracking to the external leaf of brickwork. The cracking is normally about 18 inches apart, and usually most obvious on the elevation which is most exposed to the prevailing winds and rain. There are plenty of companies that will do boroscope surveys but beware the ones that do it for "free" because they make their money by selling you wall tie replacement. D
Re cavity wall insulation - this is great in new houses where it is built into the construction - but NB there is almost always some form of cavity left. Retro fitting CWI is not an ideal solution as it fills the cavity. The cavity is there for a reason - air is not a bad insulator and the cavity also prevents transmission of damp from the outer leaf of the walls to the inner leaf. If you fill the cavity you have bridged this gap making it far easier for damp to penetrate to the inner leaf.
There are many instances where CWI works fine - but there is a risk involved. The risk increases if you are in an elevated or exposed position.
What is the risk in an exposed or elevated position?