Finding ceiling joists

[sunshinewelly]

How do I locate my ceilings joists. My living room is rectangular. I bought a cheap joist finder and think I have found some running parallel to the longer sides of the room. However the closest one to the internal wall next to stairs is around 20 inches away but there is no other one close to the internal wall. I am trying to mount a projector near to the wall but can't find a joist

 

[Tigercubrider]

Can you access the floor above?

 

[sunshinewelly]

 

[sunshinewelly]

I have marked the 2 joists with tape on ceiling. The wall behind is hollow and there are then stairs behind going upstairs.

 

[sunshinewelly]

 

[Tigercubrider]

How are you going to cable this?

There are (ugly) dual wall/ceiling brackets
You could find two joists, screw a piece of timber between them, paint it white, and mount to that
Depending on projector weight -lifting a board(s) above and putting a largish slab of timber above the ceiling, possibly to th joists as well.
Then screw through the ceiling and timber, which acts as a load spreader

 

[sunshinewelly]

Planning on running some simple trunking down the wall itself. I assumed that there would have to be some closer joist nearer to the wall or is the old 16 spacing not always accurate