Replace the whole thing. The time you will save just by cutting it out in sections will pay for the few joist you will now need.

Make it self supporting.
steve scholl

But since the deck joists go inside the house and sit on the wall plate (the wall plate and wall studs are 2x4's) how would I replace them? If I cut them off at the outside of the house, theres nothing to bolt a ledger board to. If I cut them off, take off the siding and house wrap between the joists, to slide new joists into the cavity, I'm thinking the new joists may not fit because of the weight of the wall above. Also I would think there must be some kind of blocking between the joists.

A self supporting deck that big and high doesnt sound safe to me, and having that many posts on the porch below the deck wouldnt look very good, this is the front of my house, the basement is built into the side of a hill.

28x12 is not big. its only 336 sq ft. 8 post will do the job. I can not possibly undserstand how self supporting doesn't sound safe. Why ask questions if you don't want the answers. There are huge liability issues here.
steve scholl

Free standing decks are completley safe done corectley.

If you cant cut the joists and add a ledger free standing would work. Or remove the sheetrock inside the house so you can see how the old joists went in and do the same thing although extending joists from the inside to make up the frame of an outside deck is usually a bad idea.

J.

I understand a free standing deck would be safe with the necessary diagonal bracing. The basement wall under the deck has a door and 2 windows, the 2 inside posts will end up being in front of the windows. I will try and post a diagram of how the deck joists attach to the house now. I'm just trying to get ideas how this should be done because I never seen a deck attached like this before, seems kind of odd to me.

Here is a link that might be useful: existing deck

It is intersting. How far in are the joists rotted?

Repair/replace could be done a couple ways that I see.

Tear out / Replace the same way it was done. Using a bottle jack remove each joist one at a time placing temp blocks as you go.Replace each joist one at a time.

Depending on the condition of the wood plan on installing a ledger. This is what I would do. If you can cut the joists back enough to fasten a ledger to them that would be ideal. If not cut them out one at a time using the bottle jack, place a block to the inside of the plate to hold the load, fasten the ledger to them. It would be good if the ledger landed on the bearing wall.

Ledger attachment must be firm and strong. Reread.Again.
Use the marketed steel ties, or have them made for you, for pull away protection. Install all needed flashing. Inform the permit store. Remove/replace All rotted areas including the top plate if it has gone that far.

Love the heels on that frisky blonde. J.

haha, on the heels.
The joists arent rotted, but may be a little soft on top where some decking is rotted. The beam is whats rotted, especially on the ends and where the two of them butt together (no post under where they are butted, but the joists are blocked), the 4x4 posts arent rotted either but I wanted to replace with 6x6.
If I go with the ledger on the plate, I could bolt through the ledger , block, and the first joist inside the house. Would blocks to the next joist inside for steel ties be overkill?

It is not possible to over kill a leadger attachment.

If the area where the joist go into the frame line are not rotted at all it is possible to cut them back 1 1/2''and fasten the 2x8 ledger to them.
Its odd to not have a 2 x 12 rim joists but if you made it a snug fit,had solid bearing on the framing,and fastened everything real well seems like that would work.

J.

"but may be a little soft on top where some decking is rotted"

Maybe you should go to the store and buy some of this somewhat soft wood, that way everything will match.

If its not hard it don't work and needs either wood viagra, or has to be replaced also.
steve scholl

I also think your looking at a total rebuild.

Your doing that anyway for the most part fiting in a Ledger. J.