We have an enclosed back porch room. A quarter to a third is a laundry / half bath. The rest of the area is an open room. This is the area where the problem is. Ours is a 1917 farmhouse. The issue is the windows were not sealed when installed and have been leaking for years. A few years back I realized this wall was rotten. As a temp fix I removed the outer rotten wood and replaced it with a piece of plywood and covered it with plastic until I could afford to fix it. I went into the crawl space yesterday and the floor joists are solid. They are bot pressure treated however. The inner ridge board looks great from the crawl space. I again believe the ridge board to be three 2x8s sandwiched together. I now have a little money on Lowe`s gift cards to attempt to seal this from the weather. The top of the wall appears to be 3 rough sawed true 2x4s that support the roof. Question 1. The opening for the door can not be raised and there is not enough room to place a header between the 2x4s and the door. We have lived here 9 years without this causing issues with the door. Will this be okay to just replace the door? Question 2, When I saw that the inner 2x8 for the floor was okay I was happy as my disability is a back issue. However the outer 2 2x8s are rotten and I believe they have softened that side of the inner board. I thought that I saw an epoxy product that could be used on this board to strengthen it before replacing the two outer boards. Is this a possibility? I only ask as I am not sure I could work in the crawl space to build a support wall to carry the load while I replace the ridge boards. Any information will be helpful. Thanks.

to epoxy a rotting board, This Old House had to use a pressure-injection system. you and I don't have one.

one of the contractors who periodically visits the boards might have a suggestion, but from where I sit as a plain old Joe who DIYs, you are going to have to support the porch/room and take off and replace those two creepy boards.

anything that touches ground and is NOT treated needs to be buttressed from the ground with metal flashing underneath. might be a real good idea to paint it with "edge treat" bluewood or creosote all around as well, but again, listen to any of the pros.

Really need some pictures of the effected areas.
It's fine to to do a small repair on a nonstructual piece of wood such as a piece of trim, but never on something like a rim joist, foundaton plate, floor joist and any wall studs ECT.
Any rotted wood really needs to be replaced not just patched if you want this to last.
Once we see some pictures the suggestion will come.

Thanks! I was afraid of that. I will be using pressure treated for the replacement wood. However the wood does not touch the ground. Water has been running down the inside of the wall due to improper installation of the windows. Now to figure out the support system. If I can not work something from the sides I guess I will have to pour cement footings to support the temporary (may be permanent) support as the ground underneath is soft undisturbed sand.
Another question. They did not insulate. If I want to insulate and use plastic underneath I guess we will use un-faced correct? Finances allowing I will use 1/4 inch plywood. Pressure treated of although the wood seems untouched by weather even though it is only protected from outside elements by plastic lattice.
Thanks for all of your help. Even a novice can know the correct information.

Joe it is raining today. I have some pics of the outer rot which is total destruction. The two outer 2x8s have decayed in the center. I will need to remove these to see how bad the damage is to the inner 2x8. I will attempt to get pictures then. Thanks.

The only wood that should be pressure treated is the bottom plate in the wall.
If the outside is sheathed, house wrapped, and the window reinstalled correctly then the wall is sided correctly there is 0 need for pressure treated anything but that plate.
Pressure treated wood is againt code to be used indoors and anything that touches it would have to be ACQ approved including any nails or fastners to install it and to attach the sheetrock.
No clue what the bottom part of your post was trying to say. Not sure how 1/4" plywood, lattis and all that other stuff comes into play.
Really need a picture.

Here is a base picture. I have others, but can only post one at a time I guess.

Picture 2

Picture 3. Keep in mind that the ridge board consists of 3 2x8s. I believe there is some minor rot beginning on the face of the inner 2x8. Thanks.

gut reaction: gut.

if the sides are OK tip to toe, you can probably support the roof temporarily by laminating some 2x6 with a plywood core (screws and glue) sticking out to the sides, and rest that in an A-frame of similar construction.

then tear out that bad, bad wall and redo it.

but I'm not a contractor, if one of those two guys has another idea, forget me.

The wall is not the issue. It is just floating now so replacing it is a dream. The floor is the nightmare.

How so? Simple enough to just cut it out and replace.
I'm working on one right now that the old home owner built the walls on top of the old open deck, they set the bottom plates leaving 1-1/2 of the old decking sticking out and left it exposed, they only layed 1/4 louon on the inside floor.
No house wrap, no window tape on the windows. So it looked far worst then yours.

My back issues make it difficult to work under the porch to support the floor. What is your opinion to placing 1/4 inch plywood on the under side of the porch after the insulation? Will the better weather proof (cut down drafts) or be over kill?

That would form a vaper barrier on the wrong side of the joist and trap moisture under the floor.
Far better to use 2" foam directly under the subfloor, use spray expanding foam to seal any gaps.

Thank you all for your help.