Water leakage thru house type siding

[stevieb]

My neighbors have a 1973 Burlington with regular house type siding.
In one area of the home the floor sank and we cut away the flooring to discover black mold and wetness on the sill. We removed the insulation on the outside wall to discover that the siding has weep holes in it. The wall insulation is sopping wet about half way up. The home does have a metal roof over with an overhang and the water damage is not at the ceiling level but ony about half way up the wall.
How do we prevent water from coming in after we repair the floor and put new insulation in the wall? The weep holes are not plugged up as we can see light thru them.
My thinking was to put plastic between the studs and tuck the bottom edge over the sill towards the outside to allow the water to run out that way. But even than it would make the underbelly insulation wet!
As you can imagine they are very concerned this is happening in other areas. What a terrible way to build soemthing! I understand the concept of allowing the walls to breathe but this is just crazy!
Thanks for your help in advance Steve

[stevieb]

We just found out there is NO vapor barrier on any of the homes walls. BINGO!
The interior of the outside wall in this room will be removed completly, sill repaired, new insulation,vapor barrier and new paneling.