Dark/Damp patch on new insulated slab corner

[Waddell]

Hi,

I recently laid down a new insulated concrete slab for my new garden room. I have drawn and attached the slab detail.

I have noticed a dark damp patch in the corner under the DPC I've laid under the timber frame.

There hasn't been much rain and the dampness is a brown-ish colour.

Would this be dampness rising through the slab from a hole in the either of the DPMs? I have attached a photo of the damp patch.

I have access to dig up the ground outside where this slab is so I could dig out the area to find the hole if this is the case, not sure what else it could be.

Any views/opinions would be greatly appreciated.

 

[plockhart]

Hi! This is me, except you have the benefit of a few years. My construction is the same except I have an additional DPM laid on top of the concrete for the interior finish. I suspect it is condensation I am seeing. The room is still under construction and looks like it is a similar state to yours - except I still have conduit holes in the walls, the windows kept ajar to run temporary power, and no external cladding on. So lots of different contributing factors.

What happened in the end? Did you do anything or how did it all pan out?