Mdf or k plyfa for floor hatch?

[olofh]

I am planning to cover over a brick-lined pit that previously served as a pantry. The pit functioned as a sort of cold storage. I'm considering what type of board to use, MDF or K plywood. I'm thinking of using approximately 19mm MDF or 15ply. I plan to lay tiles on top later. I'd like to space the joists as sparsely as possible underneath to avoid losing space. Part of the board I will cut out and make into a hatch.

Which board and what center-to-center distance do you recommend to avoid flexing?

 

[Cheesen]

How big is the hole?

 

[olofh]

How big is the hole?

110 wide and 90 deep. There will be two 60x60 wardrobes standing on it so the actual hatch should be in front. But mostly wondering how I can get it to support the wardrobes

 

[prototypen]

MDF goes away.
22 mm chipboard/floor chipboard is the first choice.

Protte

 

[olofh]

MDF is a no-go.
22 mm chipboard / floor particle board is usually the first choice.

Protte

Ah! That completely slipped my mind. How closely do you usually space the supports for floor particle board?

 

[tergo]

22 mm floor chipboard joists c/c 600 mm