Concrete floor worries

JuzaMum

10 years ago I had a single storey extension added to my house. This extended the kitchen and added a bedroom with en-suite. Last weekend we took up the lino in the kitchen end and found it was wet underneath. The next morning it had all dried out so I assume to cause of the wetness is not a major leak.
Today it is raining and there is a damp border along the outside wall which includes patio doors. I can only see along one wall without moving furniture. The waste pipes from the ensuite go under the floor. I assume the water supply to the ensuite also goes under the floor too. I think the radiator pipes are in the wall. The wetness appeared clean and was not smelly.
We are changing the layout so the ensuite will be removed soon and the dividing stud walls removed.
Obviously before we put anything in the space we need to make sure everything is sound.
What investigations should I be doing? Could my damp course be faulty? Is this something I should be discussing with my insurers?
Any help or suggestion gratefully received.

Ainsley1

So many possibilities and without seeing/knowing the property it is difficult to know where to start!

Could it be condensation running down the outside wall on to the floor?
Try directing a hose around the door area from the outside to see if you have a leak?
What type of construction is the extension? Cavity wall, timber frame, are the gutters choked up?
Does sound like a weather related issue (damp following rain) but a clean water leak cannot be ruled out.

Can you see any cracks or moved joints between the old and the new extension?

If the dampness has been happening for a while it could well have become trapped under the floor covering. Chances are if the extension has been impervious to water after all that time it will be a maintenance issue.

You could call in a surveyor to come and do a dampness test? Choose a member of the RICS. That will be the best but most costly option if you cannot locate a problem.

Whatever route best get it sorted before any new work.

JEN22

Could well just be lack of ventilation and no damp whatsoever

JuzaMum

There is no visible condensation on the walls and there was no wetness on top of the lino when it was there.
The extension is block work cavity walls with celotex insulation.
The damp border is even all along the wall 4-5 inches.
Roof and gutters are good.

Doozergirl

Photographs, please!

JuzaMum

JEN22

The lino has been trapping moisture from the cold floor. I have this problem its just condensation. Given room to breath it will dry out

JuzaMum

Grr photobucket! Thanks all for your input. The damp area that I found when I took the lino up has shown no sign of reappearing. When the room is totally empty I will be able to look at the whole thing and maybe get an idea of the problem if there is one?