I have a damp problem which appears to be coming from the strip of floor just inside my patio doors. Originally this damp was believed to be due to a leaking pipe, so a channel to the room side of this strip has been excavated to show the pipes.
To clarify - considering the view from the inside out there is:
Floor slab Channel in floor with pipes in right on edge of slab Edge of floor dpm Inner leaf of block work with concrete capping to level with existing floor Inside face of patio door
The damp proof membrane for the original main slab ties into the wall dpc at top of main slab level. This means that any dpc/membrane below the strip of floor immediately inside the patio door (above the inner block leaf) can only have a membrane below the level of the wall dpc alongside it. I should point out that this patio door is not an original feature of the property and is effectively a window extended to ground level IYSWIM, although a patio door has been there for 20 years or so.
So I guess the questions are to do with the way this area should be made up. If this door was installed from scratch, the brickwork would be cut down below the window but what then?
1. Is the exposed cavity filled with anything down to foundation level (concrete)? 2. How is the dpm for the room slab connected to dpc under this strip of added "floor"? 3. Should the floor strip be just concrete, cast over dpc? 4. How is the concrete strip supported over the cavity, if the cavity isn't filled?
Having poked about a bit, the damp appears to be coming from the area outside the main floor dpm, under this strip of floor. Under the concrete strip there seems to be loose sandy stuff. I am looking at a small area alongside the pipe channel about 600 (2') long. Although there is some dpm under the strip it is clearly damaged in parts. The insurance company put some driers in over the past fortnight, but within an hour or two of them being turned off, damp came back to the sandy area beneath the floor strip. If there is no "active" water source (i e. if it were down to ground water only) would damp reappear that quickly?
Anyone who's read this far deserves a medal - any help or advice appreciated.