Due to water exposure, the bottom part of the door frame has rusted and also made the bottom part of the door swollen.

How to solve this kind of problem in long term? Or what kind of door frame and door to use to prevent this from happening?

change to aluminium frame and plastic door panel.

i did this during renovation, my contractor told me it's worth it for long-term use, especially in a wet room such as toilet.

Roughly how much do you spent on changing to aluminum door frame and also plastic door panel?

forgotten jor. it was many years back when i renovated my landed unit.

Within 1k should be able to do it but depend on the charge of the installer

Plastic door?

That look cheap and ugly wor.

If its a shower bathroom, I would relocate that door or put in a shower screen with a shower tray..

If it is an external door then put up a roof and a front porch to minimize water damage to the door..

Standard building designs don't allow standing water anywhere near a door frame..

atkc banting e-order quite cheap for plastic door. only iron frame. need to find own installer.

The door I have is with shower bathroom.
Even with shower screen and shower tray, sometimes I will wash the entire bathroom floor and it is inevitable that water will splash on the door frame and door.

I do know that right after the floor washing, it is advisable to dry the door frame and door right away. You know, sometimes I am just lazy

If it's just the bottom part can't you send the door to a carpenter to remove the timber plywood laminate and replace it with a plastic or water proof laminate?

If you can DIY then it might be easier to just cut the damaged part and replace it..

That's if you don't mind the look..

I put cement/tiles ontop of the bottom frame. Dont know if rusted inside, but still looks good untill now.

Normally your toilet floor is below the room floor. The door is higher from the toilet floor. That mean your water splashing much be strong. Use the hose to get nearer to the place you want to wash. Don't splash. Or use mob to clean like other room.

All my bathroom door and frame is wood. I have trim it before back to 18yrs ago. Normally the new door and frame of new home will expand. Cause by water and humid. That is normal.

But till now, no more such problem happen. What I do is,

1) Paint the door and frame with oil paint. Every inch of the door (specially bottom) and gap is seal off with paint. So water cannot sip in.
2) Wash the toilet floor by hose. That limit the water splashing everywhere.

Anyway, I can DIY repair the door and frame when such problem happen.