How thick a diagonal brace is needed in a homemade door?

[Holpers]

Building a new storage door.
110x220cm. Odd dimensions.
Framed 45x70 with 22 mm wooden panel on the outside and plywood on the inside.
Planning to have some stone wool boards or polystyrene in the door.

Need to have a diagonal brace.
Is a 20 mm board enough?
Thinking that it should only prevent the door from sagging and becoming rhombic. So, no major weights.

 

[Workingclasshero]

Hello
Cut a bevel on the inside of the door frame that has the same or larger dimensions as the plywood sheet.
That is, you inset the sheet into the door frame.
There you attach the plywood sheet, it will be stable as hell!
If you also add a diagonal brace, it reduces the risk of the door warping.
/W

 

[Holpers]

Hi
Mill an edge on the inside of the door frame that has the same or larger dimensions as the plywood board.
In other words, you recess the board into the door frame.
That's where you attach the plywood board, it will be stable as hell!
If you also add a diagonal brace, the risk of the door warping is reduced.
/W

Good idea but then I won't have room for 70mm of Styrofoam in the door.

 

[Thomas_Blekinge]

Is it worth having insulation? Is the storage insulated by the way?

 

[Workingclasshero]

Good idea but then I won't have space for 70mm foam in the door.

Cut deeper and use 50mm foam, you'll never notice any difference.
/W

 

[optimizer]

The door cannot become rhomboid with a plywood on the inside.

 

[Holpers]

Is it worth it with insulation? Is the storage insulated otherwise?

Yes, the rest is 30cm ytong blocks.

 

[Holpers]

Dig deeper and use 50mm of Styrofoam, you'll never notice any difference.
/W

I can glue and screw plywood on the inside. Then it will stay in place.

 

[Holpers]

The door cannot become rhombic with a plywood on the inside.

I was thinking of gluing and screwing with a 42mm wood screw.
The diagonal brace adds a bit of extra stability, I think.