Fix for leak between metal and plastic roof?

The shed where I keep the tractor, trailer, lawnmower and the old Explorer has a standing seam metal roof. A prior owner built a workshop on the back, with a corrugated plastic roof.
The overhang under which the plastic was tucked is very short - maybe two inches - and the slope of the plastic very gentle. As a result, water flows back under the overhang and drips onto the floor, rotting it. I have replaced the rotted oak floor and several joists and tried to fill the gap with foam in the valleys of the corrugated plastic and on the outside, roofing tar. The darn thing still leaks (though less), three applications of tar later.

Can anyone recommend a particular kind of spray or goop that will seal this joint better than roofing tar? Tearing off the plastic roof, cutting into the overhang and re-timbering the roof on the back of the shed is a job I will go to some length to avoid.

Two inches of rain this weekend inspire me to tackle this mess. A picture would just confirm the mess I've made with the foam and tar.

Chas

When I had my pole barn built, actually two barns, one end of one is attached to the side of the other, the builder sealed the seam with silicone.

No leaks, and we have had some 5 inch rain storms since it has been built. [img]/forums/images/icons/smile.gif[/img]

What about putting a gutter along the edge under the main roof, or alternately extending the main roof down to the plastic by screwing an extension to the undersdie of the existing roof.
Or screw a piece of flashing to the plastic roof and add mre cement extending the vertical lip under the existing roof line..

Carl

Carl, Dumbdog,

Thanks for the good ideas. I think (or I fear) there may be no substitute for getting up there and ripping out the tar and indeed putting some flashing under the metal and extending out along the plastic. I was hoping of course that someone had some magic aerosol that would seal everything up and let me keep this as a fix, not a project...I'll look if a silicone spray exists. Before it gets too cold to apply anything.

Chas