Strange Joist on top of (non-load-bearing) kitchen/dining room wall

[WoOt]

Looking to DIY remove the wall between our kitchen and dining room, and from what I've read and can see it's not load-bearing. Just looking for a second (third, fourth,...) opinion as I'm a little confused by the fact that the joist on top of it is different (smaller) to the other joists.
Quick plan of the house for reference:

Steps I took:

1. Checked the floorboards:
   1. They run perpendicular to the wall
2. Went upstairs and lifted a floorboard on top of the wall
   1. Joists run parallel to the wall
3. Looked at the joist that is directly on top of the wall, which is where I'm getting a bit confused:
   1. First thing I noticed was that the joist on top of the wall is different to the adjacent joists (or at least the two I can see).
      
      The red line always shows where the wall below it is
      
   2. Looking at the joist on top of the wall, I can see four layers (in this exact order, starting from the wall below):
      
      1. Foil backed plasterboard (I think)
      2. What looks like a single tongue and groove type plank (floorboard?)
      3. A joist with less height than the adjacent ones
      4. Another piece of timber that is laying flat on top

 

[WoOt]

Not sure how clear these pictures are now I look at them online. I can try and get some better ones if it's not clear!

 

[johnny2007]

Looks like a packing job to me.
If other joists are spaced correctly you can simply remove it, however i expect that piece of timber to be nailed to the floorboards.
Open up the ceiling downstairs to have a better look, there might be cross members.
Cut a line of the ceiling parallel to the wall, about a foot so to have easy access.
Any walls upstairs?
Built in wardrobes?

 

[WoOt]

Looks like a packing job to me.
If other joists are spaced correctly you can simply remove it, however i expect that piece of timber to be nailed to the floorboards.

Looks like the joists are approx. 340mm apart (measured from the center of each). The floorboards have indeed been nailed to the piece of timber sat on top of this "strange joist".

Open up the ceiling downstairs to have a better look, there might be cross members.

There are no cross members I can see. In fact, it looks like this "strange joist" isn't a joist at all, as it doesn't run the length of the wall and doesn't seem to be sat on the outside walls.

On the image above (to the right) you can clearly see the bricks and mortar from the wall below. Looks like the plasterboard does not run underneath the wood as I initially expected. This is looking towards the hallway.

This is the other side of the "strange joist", still facing towards the hallway.

And just to be complete, here is one of each side of the "strange joist" looking towards the garden:

Any walls upstairs? Built in wardrobes?

Yes, some built in wardrobes above. The red line once again shows the approximate position of the wall.

 

[johnny2007]

Ok, the 2 wardrobes might be supported by this wall, unless they span across joists.
I take that they're not made of bricks, but just timber.
The 2 wardrobe walls i marked in blue should be completely independent of the wall downstairs, make sure of that.
If that's the case, you can remove the wall and the packing (strange joist).

 

[WoOt]

I take that they're not made of bricks, but just timber.

Some ventilation gaps between the two cupboards reveal they are made of concrete blocks. As is the airing cupboard

The 2 wardrobe walls i marked in blue should be completely independent of the wall downstairs, make sure of that.

The vertical blue walls are approx. 460mm away from the red line which marks the "strange joist" and the wall underneath. The two horizontal green walls depict the sides of the cupboards, which do cross the wall (and at least two proper joists). These two joists are 175mm by 55mm as far as I can tell.

Is it worth taking out more floorboards to see if there are joists directly underneath the cupboard walls? The (175mm by 55mm) joists that are visible are approx. 340mm apart. If they are all spread out like this, then the next batch would not sit directly under the vertical blue cupboard walls, but approx 50mm past them.

 

[johnny2007]

You need to investigate what is supporting the 2 blue walls.

 

[WoOt]

Ran out of batteries on the multi-tool (cheap aldi junk). Will try again tomorrow.

 

[WoOt]

Finally have another picture (life got in the way). Joist 1 sits near the blue line depicting the built in cupboard wall in bedroom 2, but isn't exactly underneath it.

• Distance from Joist 1 to Joist 2 is 400mm
• Distance from Joist 2 to Joist 3 is 340mm
• Distance from Joist 2 to the "strange joist" is 160mm
• Distance from "strange joist" to Joist 3 is 180mm