Building a wardrobe over stairwell

[Rs82uk]

I want to maximize the space in my sons small bedroom by creating him some storage utilizing the large stairwell that protrudes into his room.
I am aware I need to maintain head clearance on the stairs so the bottom of the wardrobe will be a couple of feet off the floor in the room, but that's fine.
I am pretty much fine with what I need to do to create the new wall. What I am not sure on is the base, as there is a chance that a kid might climb in I want to make sure the base can take some weight. The stairwell is brick one side and stud wall the other. How would be best to create the base of this storage space.

Thanks in advance

 

[^woody^]

4x2 and 18mm ply or mdf

 

[Rs82uk]

Thanks alot and in terms of anchoring it I guess screw into the existing studs on two sides?
And then what would you recommend to secure the 4x2 to the brick wall?

 

[dontbelieveawordofit]

frame fixings.

 

[dontbelieveawordofit]

can we see a picture of the large protruding stairwell?

 

[^woody^]

Screws and brown plugs for both.

 

[Rs82uk]

Here is the stairwell in question

 

[Tigercubrider]

What I think is a version of your situation in my house is that the stairs ceiling is continued, at the same angle as the stairs for headroom, the inside of the cupboard is also sloped but boarded. There is a horizontal shelf at the base of the cupboard (if you have a kid make sure it would take his/her weight) the small sloped area's handy for shoes.

Not that I have tried, but the structure would probably take an adult's weight. The back of the cupboard is brick.

 

[Rs82uk]

Thanks this is exactly my plan as advised above I'm making the base out of 2x4 and ply to give as much strength as possible to take some weight if needed