looked at a job last night, guy has a house high on grade, then the garage is on the lower grade attached to home. Roof of this garage is flat and previous owner used rubber membrane over the roof deck. The house itelf has a walk out exterior door that allows access to the flat roof where this new homeowner has his grill set-up and laid outdoor carpet over the rubber membrane since there is a railing around perimeter of flat roof it's essentially a "deck".

Problem area: the exterior door that exits onto flat roof, when they installed the membrane they rolled the edge against the house up under the bottom row of cedar siding, but then where it meets the sill of the exterior door they cut it off to be flush with front of sill then used some sort of sealer around brickmold and sill. Well, the sealer has breeched and as a result water has penetrated into the unfinished garage space. The under side of the roof deck has a stain but still appears very intact, the bottom plate for the house in this are has rotted and at some point where some rot was at they installed some expanda foam to seal the missing/rotted wood.

So, my problem: they want the sole plate that is rotten removed and replaced. If I fight it I think it can be done from inside lower garage with proper jacking to remove pressure off joists to slice it out and hammer in new. Now my question, what would be the best method to redo the roof area under the exterior door to prevent future water damage/water entry? I was thinking about removing the exterior door to check and see if plywood subfloor is still intact-replace if bad since door sit's directly on kitchens sub-floor. Then cut out a section of the rubber membrane and laid down a new piece extending to area under door. Seal the membrane to the homes sub-floor and try to make my own rubber corners to fuse to exterior side of membrane and the membrane that's now going to be under the door. After that aspect is done use a sealer of some sort across sill before setting door so if/when water does penetrate the leading edge of door sill the sealer under the sill will prevent it from going any further, then any water would still be sitting ontop of membrane and not leaking into lower garage.

Jim_Lincoln

I would have your HVAC man or metal specialist make a galv. pan to go on the subfloor and under the door. All seams should be soldered.The pan should overlap the rubber roofing where they cut it around the door. And also up the sides of the trimmer studs. You may have to remove some siding to make sure the pan is fully sealed. Seal with silicone before setting the pan, then seal with silicone before setting the door.

Does this make any sense or should I be more elaborate?

Otherwise, I do like your idea of the rubber membrane in place of the pan.........Remember............Think like water, where will I go when I hit the side of this wall at 20 mph.