Internal door frames crack

bjorn_toby_wilde

It does look like rot and the marks on the wall are suggestive of water getting behind it somehow, either from a leak or damp.

Where is it in the house? Upstairs, downstairs, on an outside wall?

WIAWSNB

What's on the other side of that wall? Outside?

And is that doorway an original feature?

Anyhoo, that looks like pretty extreme wood rot, most likely 'wet', and very possible emanating from the ground - the skirtings look damp? Could even have started as wet, and become 'dry' :-(

I fear it needs a professional investigation to ensure the cause is also fixed, and any 'dry' is thoroughly treated, right into the wall. 

Don't panic, tho' - it's all standard stuff. 

Snowy2018

It's downstairs, otherside is bathroom but no sink, shower or toilet directly behind, just a wall.

Original feature, unsure.

stuart45

There could be pipes chased into the wall, going down to the floor and under it to the bath etc.

Snowy2018

Trying to think which trade is best to come out and look.

Plumber, carpenter or builder? 

Grenage

Well you don't know if you have pipes to repair, and there's no point in getting a carpenter if the problem is still there.

A handyman might be alright for identifying the problem.  Is the wood or any of the surrounding area damp?  Is it historic?  You might as well pull the soft/ rotten wood out and have a proper look.

bjorn_toby_wilde

Snowy2018 said:

Trying to think which trade is best to come out and look.

Plumber, carpenter or builder? 

Of those three, builder.

the_lunatic_is_in_my_head

I’d say the door frame has had it, would your friend object to you removing it, you could then see if there’s any signs of damp/water behind the frame.