Help please re damp problem

[insanelycheerful]

It seems we have a problem with damp in one corner of our living room, affecting two walls as it's in the corner. I have no idea how to go about getting this looked at and sorted! I'm guessing it could be quite expensive to put right (sorting the cause of the damp as well as re plastering and painting the internal wall, and possibly the external rendering etc?) so perhaps something to be claimed on our buildings insurance? Who do I contact first? Insurance co? A builder? Do I have to use an "approved" workman? Where do I start?! Sorry I am so clueless!

Also any idea of how much this might cost me would be v helpful.

Lurk as we have exactly the same problem. I suspect the render as it's a bit cracked on that corner but no idea who to call or how to sort it

The first thing is to work out what's causing the damp. Before doing anything expensive start looking yourself. You mention render - is it cracked and letting water in? If so repair the render and let the damp dry out. Check gutters/downpipes aren't broken or blocked & leaking. Internal pipe work - any hidden leaks (look under floor)
Do not get a damp proofing company in to give you a free damp survey - this is just an expensive sales pitch that won't necessarily solve your problem.
There are lots of causes of damp, injectable damp proofing only really solves one of these.
If you can't work it out then consider paying for an expert survey, these guys don't do the remedial work but will advise you what you need doing.
If you find the cause yourself and have it fixed. Let the interior walls thoroughly dry out and then treat with a stain stop before redecorating otherwise the stain will eventually leak back through.

First step is to try and work out what is causing it. It could be something simple like a blocked drain or gutter. These things are easily solved.

A rendering company will repair or replace render.

Thanks for replies

A quick bit of online research reveals it is rising damp. Render doesn't appear cracked/damaged as such. It's on an exposed corner and the render (painted white) is discoloured where I assume the damp problem is, it's darker and slightly greenish. Internally the plaster is cracked, split and peeling and a tide mark is visible.

What work would be done to rectify this?