Cutting out a new internal doorway. Advice needed please?

[MettyMatty]

Hi,

I need to cut out a standard sized internal doorway in a 100mm thick concrete block wall that's supporting the floor joists above.
The wall runs from the front to back of the house which is about 5.5m and there's already a door about half a metre in from the front end that I intend to board over.
The new opening will be at the opposite end from the existing door in a similar position. The ceiling joist ends protrude 5 inches through the supporting wall. The joists are 8" x 2" at 400 centres and are sat on a course of standard house bricks. The concrete blocks below that is where I'd have to cut the lower halves away to fit the lintel.
As haven't attempted this before I have a few questions...
The ground floor is suspended. Is it acceptable to use acro props on a suspended floor if place over the joists?
As I only have 5" of the ceiling joists protruding could I use 'strongboy' brackets directly on the joists so that I have clearance to make the cuts etc..? Acros on their own will be too tight to work.

Any advice please?

 

[^woody^]

You should use a batten on the floor across several joists. Likewise for the ceiling, and not a strongboy - as the joists will hold up the wall. Set the prop back enough to allow you to work between it and the wall

 

[oldbutnotdead]

Usual batten being scaff planks or 6 x 2