Turn off all taps in house. Check your water meter and record number. Come back an hour or more later 9longer the better for small leak) and see if it has moved to indicate a leak first. Discount any dripping taps by catching an measuring that water.

Ideally the copper pipes should have been wrapped to insulate against the concrete expansion and contraction. However , that is not often done. How old is the extension that has the concrete slab? It looks like it is already failing, doesn’t look like one piece of poured concrete it looks like broken concrete. Is the actual concrete slab cracked and bringing in moisture? Good suggestion by Kate to monitor the water to check for water leak. But it may be ground moisture coming through the concrete.

@dreamer Thanks for your response. To answer your questions:

How old is the extension that has the concrete slab?

The extension was done in the past 2-3 years. The previous owners did the extension and we bought and moved in last year.

It looks like it is already failing, doesn’t look like one piece of poured concrete it looks like broken concrete.

I think the concrete slab is above the red sheet. I am not sure what is surrounding the pipes.

Is the actual concrete slab cracked and bringing in moisture? But it may be ground moisture coming through the concrete.

Not that I know of. The ground under the house is definitely damp. We are on sloped land and believe there is rainwater going under the house through the soil due to lack of appropriate sub-ground drainage in the backyard to capture and divert the water from going under the house.

Maybe, with your last paragraph, you have answered your own question as to why your house has high moisture.

Stop water running under your home, Construct a drain across your home, A plumber would be best advice. Underneath your home should be always Dry