Originally a bungalow, room in roof added in 70s. Wall between room and loft space is single skin clay perforated block.It would be interesting to know what you're doing.
Because of an extension on the front, we are losing the loft hatch. I've decided to replace with a concealed access door through the wall. Probably one of the these at about 600w x 750h.
Insulated & Air Tested Fire Rated Access Panels | Picture Frame
Insulated and Air Tested Fire Rated Access Panel with Picture frame 1 Hour Fire Rated - Tested to BS EN 1634-1:2008 (wall) and BS EN 1634-2:1999 (ceiling) • 36dB sound reduction on UKAS test• BS EN 1634-3: 2004 Smoke Test (15 times better than the required standard)• Insulated and Air...
www.jupiterblue.co.uk
When I've made the opening I'll think about whether it needs a softwood casing or similar but I'm hoping I can foam the hatch straight into the rough opening and then tidy the rough edges with a bit of 50mm angle trim.
I'm also insulting the wall with 100mm foiled celotex foamed onto the block on the cold side.