On my lapsided house, the ledger board for the wood deck was mounted without flashing. This caused the rim board to rot and must be replaced. The rim board is standard 1X material and not engineered. The floor joist run perpendicular to the rim board. The home sits on a crawl space. There is access to the rim board via the crawl or under the wood deck. What would be the best way to replace the rim board?

Isn't the deck right in your way? Maybe a picture would help us, any chance?

I have had to do this. First, it is important that you have full access, which means you have to access the side that is rotten. My bet - the deck side.
(Are you sure it's a 1 x ? Rim joist?? )

If the rim joist is rotten, there is a large chance that your sill plate is too.
Like Ballenger says - a picture is worth a hundred words.

Thank you gentlemen for your prompt response.
The ledger board for the deck is secured to the rim board with Large Zinc woodscrews.
Yes, I have access to the rotted side via crawlspace.
The rim board consists of either one or two 2X8's. (My error).
I should get some pics tomorrow.

These are pictures of the rim board from the crawl space. Note, the band board sits atop a girder.
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This band board is underneath the threshold of a door in another post.

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Another attempt to provide the pictures.

I am a little concerned about the uninsulated PVC supply lines, where do you live?

I can see lots of water stains on the rim joist but I can't see how soft the wood is. Unless the rim joist is really soft, I would install blocking between the floor joist. Cut them tight and toe nail into floor joist. Also make sure that they are pressed up against the flooring. The rim joist keep the floor joist perpendicular, support the floor and supports the plate of the wall above. The added blocking will do all of these things. If you cut out the existing rim joist, how are you going to nail the sole plate of the wall back down without removing the siding up to that point. The blocking, toe nailed into the floor joist, will be just a strong if not stronger, than the rim joist which is face nailed into the floor joist.

I have this same problem at my house. Even though I know it's a major undertaking, wouldn't it be better to take the deck down and replace the board? My husband and I "patched" it up, but I'm not happy with it.

Location of the home is Charlotte, NC area. Since the home is a rental unit, I am going to block the floor joist next to the rim board. Next step is to remove the door complex and r & r any damaged wood. Replace the door with a new jam. Flash the ledger board for the deck. Finally, replace the siding and caulk. I believe this can all be accomplished with less than $200 in materials and sweat equity.

You know that whatever is screwed/nailed into the rim board on the exterior is also going to give a path for water. My bet that that board is soft in places and it should be replaced at that section.

It doesn't look like a double rim joist, so you will need to take off that deck so you can access that rim joist and jack up
That part so you can replace it. The pictures show there may be some rot, or something not right on plate of the foundation as well at one location in your pic.

After you disconnect the deck, you will need to use flloor jacks that are postioned on something sturdy. What is located above
That floor that we see in the picture? I see water lines, so you would have to make sure that you have some give when you jack
The house up a little. You only need to jack it up just enough to do your repair. Getting that rim joist out without jacking that portion up may work, but doubtful and when you replace that
You will difinately need the room. When you do this, check to see what condition the sill plate is in as well. I can help you get through this, (and so can others) but if you are not comfortable with this type of job - you may want someone else to do it.

It seems like a lot of work and having someone to help you do it will be smart. Let us know.

I just looked at the pics again. If you look, there is some area's on the joist's that run to your rim joist look like they may be bad as well. It's a pic, so I am going on experience.

One pic shows that the sill plate ends (the board that sits on your foundation block),
And something else starts from that location and moves to the left. That doesn't look so good either. Do you know what material that is?

Good luck! At my house, I'd still like to take down the deck, replace the board, then put the deck back up piece by piece. Is this feasible, or do I need to use all new wood? There's nothing wrong with my deck wood now, but would rebuilding it make it weak?

Thanks.

Bearsmom, just like everything... it's what materials you use and how you build. I cannot see your deck, so I cannot tell you from here. Taking your deck a part may not need you to dismantle it piece by piece either. Take a look at your connections to your posts, to the house etc. You can take off a few deck board if you need to see your connections better.

You can also just replace what looks "iffy" and keep the rest. Again, you should make sure you understand how to rebuild it, if you do that.

As for the rim joist. If you have a crawl space, you will need to have room and good sturdy place for your jacks.
You will want to make sure that anything above that area that you are jacking up (pipes, etc) won't be damaged.
(sometimes tile will crack at joints) but inspect what you will be moving just in case.

Possible damage that you cannot see: the ends of the joists that run perp and to that rim joist. In that case, be prepared to add new ones right along next to them. The sill plate in that area, etc.