How I Replaced A Rotted Rim Joist And Sill Plates – Part 4 of 4

Part IV of the article series describes the removal and replacement of a rotted rim joist and sill plates with new pressure treated lumber.

Please note that this is more-serious-than-normal DIY project. It can potentially cause severe property damage and injury or death!
How to Replace a Rotted Rim Joist and Sill Plates is a multi-part series article, broken into Part 1, Part 2, Part 3, and Part 4 (you are here).


  • Various crow bars
  • Claw / mash hammer
  • Framing square
  • Circular saw
  • Wood chisel
  • Work gloves
  • Eye protection
  • Reciprocating saw
  • Sill seal
  • Tube of caulking / caulking gun
  • 2 1/2″ Deck Mate Screws
  • 5/8″ Wedge anchor


Step 1 – Remove the loosely installed strip of 1/2″ plywood (fig.7.1.d) covering the rotted rim joist and sill plates. (fig.7.1.a=Tyvek house wrap, fig.1.2.c=basement wall)

Step 2 – With concrete patio out of the way, I can now take a better assess the water damage. As expected, the bottom sill plate in this section is pretty much gone and so is most of the top sill plate (fig.7.2). Rim joist doesn’t look too bad but I need a closer look.

Step 3 – A closer look at the rotted sections reveal bunched up soft materials? What the heck?! (fig.7.3)

Step 4 – With debris removed, I can indeed confirm that there was enough space for a small animal to take up residence (fig.7.4)

Step 5 – In order to take a full view of the rim joist, I took my trusty old Black and Decker corded circular saw and set the depth slightly less than 3/4″ thick. Then using a combination of a torpedo level and 6 ft level, I drew an outline of a long rectangle on the 3/4″ exterior plywood for removal.

Step 6 – With additional plywood out of the way, I could now see the affected area in its entirety. What I saw was a significant rot on the top part of the rim joist due. This is most likely due to the fact that the old kitchen door sill used to rest on the deck with absolutely no flashing. In addition, I suspect that lag bolts from the deck header probably allowed moisture to collect at the rim joist. Again, with not even a minimum flashing would have allowed a ton of water penetration. The old adage of “they don’t build like they used to” does NOT apply here. Truly an epic failure on the part of previous owner and/or contractor.

Step 7 – Using a combination of circular saw, crow bar and wood chisel, carefully remove small sections at a time. Note (fig 7.8) how years of moisture disintegrated a large portion of the rim joist.

Step 8 – With rotted rim joist out of the way, I tackled removing the rotted top sill plate next by marking the cut with my metal speed square.

Step 9 – I then used my Porter Cable reciprocating saw to cut the top plate as well as cut the toe nails (from floor joist to top plate). Rather than using my stock reciprocating blades, I used a Milwaukee AX blade which had substantially thicker and taller profile, giving me increased stability while cutting.

Step 10 – When I removed the top plate, I was surprised how the bottom sill plate was virtually non-existent (fig. 8.4, fig.8.5 and fig.8.6)

Step 11 – With rotted sections removed (and the first floor joists “free floating” at this point), I went down to the basement and check the height to make sure that everything was stable (and they are)

Step 12 – After tidying up the work area, it’s fairly easy 1-2-3 steps to install new sill plates and rim joist. First, I laid down Sill Seal to prevent air penetration between the bottom sill plate and basement wall

Step 13 – Cut the bottom sill plate to correct length and test fit.

Step 14 – Cut the top sill plate to correct length and test fit. But due to structural settlement, the top plate will not go in as-is. I did not want to take a risk of possibly cracking my kitchen granite counter top so I decided not to raise the floor to a true level. Instead, I decided to notch the top sill plate by about 1/8″ inch. You can either use a wood chisel or circular saw.

Step 15 – Because sill plate ends will NOT have floor joists resting on them, I wanted to add two concrete anchors (one at each ends of sill plates) to further secure my sill plates so I drilled a hole using 5/8″ rotary concrete bit and my right angle Ryobi drill. I then installed 5/8″ x 8″ Red Head wedge anchors.

Step 16 – After installing both sill plates, I then attempted to install my rim joist but it is a very tight fit and will not go into place. Since I want it to stay tight to provide maximum stability to the area, I screwed on a scrap blocking piece and tap in a vertical lever to make the installation process easier (fig.9.6)

Step 17 – Before covering up the entire area with new 3/4″ exterior grade plywood, I caulked up any small gaps to ensure that the area is air tight.

With new rim joist and sill plates made from pressure treated wood and proper flashing and counter flashing, I expect to not have the same kinds of issues ever again.


It took a lot of planning and doing back breaking work, but the end, I got it done without costing too much money.

I hope these articles have been of some help in solving your DIY dilemma.

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Thanks and good luck with your DIY projects!

27 thoughts on “How I Replaced A Rotted Rim Joist And Sill Plates – Part 4 of 4”

  1. Verry useful info. Thank you, Yesterday I discovered that
    I have the very same problem…without the concrete..
    But about the same level of damage.
    Just psyching myself to roll up my sleaves & get stuck in.

  2. Hey Paul-

    That’s great that you don’t have to worry about the concrete.

    One suggestion is to make sure you understand what caused the rot to occur. Otherwise, your repair will have the same fate in the future.

    Remember to take lots of pictures and keep us updated!


  3. This is a great series of articles! Thanks for doin it as it helps a lot with my similar issue. There was protection between the deck ledger and the rim joist so water damaged it.

    One question… You stated you drilled holes and installed the wedge anchors and then you installed the sill plates. How did you slide in the sill plates with the anchors installed?

  4. @James-

    anchors were secured to the bottom sill plate only. To install the top sill plate, I had to notch out where these anchors were sticking up so that I could slide in the sill plate. I made the notch as small as possible (sort of jammed in against the anchors) to allow installing a washer and nut. Another suggestion is to go with a longer anchor bolt than what you think it necessary. You can always lop off the excess, rather than installing a short bolt and not have enough thread to lock down the nut.

    Hope that helps?

  5. Thank you so much for posting this, you’re a life saver! I began tackling this project last Friday however, here in Cleveland we’ve had 16 days straight rain. I’m hoping to get going on this over the weekend.

  6. @Chvygrl-

    Yikes, 16 days of rain! Hopefully the weather will improve soon. Good luck!

  7. Hi Kevin, We have a similar rotten, seems easier than yours. It is rotten under the exterior door of the back room, with only wood stairs in front of it.. I thought it seemed. We run into the problem that there is no access to the basement or crawl place for this house section. We do not have clearer picture than we would pull as much debris as we can from outside. Oh! I am sure a squirel family living there. I saw a baby running in and out. We need your advice. Thank you. Pearl

  8. Hi Pearl-

    Is your problem area sitting directly on a concrete slab / foundation?

    You cannot just remove the rotted rim section without properly supporting the floor(s) above. Hate to say it but it sounds like you may need to call in a professional to evaluation your specific situation.

    Whoever you call, just make sure they are all state licensed and don’t have any major complaints (i.e. google search, yelp, etc.)

    As far as the squirrels are concerned, you need to install some type of one way trap door so that they can get out away from your house but cannot enter, then look to temporarily seal up until your rotted rim can be replaced. Search for “excluders” to find a product that fits your size needs.

  9. Thanks for the write up – great pictures & details. This seems to be a somewhat common problem. Had to fix some sill plates at my house as well, the previous owner had dirt piled up against the siding. Needless to say I’ve since removed the dirt and don’t expect any other issues going forward.

    The bunched up fluffy stuff that you found was probably a mouse nest…had that too!

  10. @John-

    Awesome. Did you end up doing the work yourself or hire someone?

    Agreed with the mouse nest, lol.

  11. one photo shows the drill, drilling the anchor bolt hole. How did they fit the drill between the floor and the foundation?

  12. Hello Kevin –
    I plan to help a friend with rim joist problems. The 2×8 sill plate is treated, and appears to be solid. The decayed portion of rim joist, about 6 feet, is due to a non-flashed deck install — really badly done.
    My hope is that I can remove and replace the decayed length of rim joist without the need for bracing in the basement, as you had to do. I’m assuming this since the sill plate and the bearing joists themselves are still in good shape..
    Does that sound reasonable? Thanks.

  13. @Hi Fred-

    What you are proposing sounds reasonable but I would caution you with two things (please keep in mind that I am not an engineer and I say below is my personal opinion):

    1. I was surprised how sill plate damages were well hidden from the inside. If I were you, I would want to physically check to make sure they are in good shape before replacing your rim joist. A simple tool like an awl can help you poke around from both outside and inside to ensure that those sill plates are not rotted from inside.

    2. Depending on the location and degree of damage to your your rotted rim joist section, you may have difficulty sliding in the replacement due to sagging subfloor. Rubbing on some paraffin wax on the replacement rim joist will help you with that task. In addition, what I ended up doing was attaching a short blocking then pushing it up with a scrap 2×4 to give me that extra lift to slide it in (fig.9.6)

    Good luck and let me know how it worked out!


  14. I have a rotten beam to replace,
    its going to be a major job,
    Id like to send you some pictures of the job when Im done, in a few weeks/months

    your readers might find it interesting,

    I found your article looking for info on jack poles,
    very good write up.

  15. @Justin-

    Thank you for your comment. Good luck and stay safe. Would love to hear back from you once the project is completed.


  16. Hi Kevin,
    Your article is quite helpful. I’m dealing with dry rot at front and rear of a job where poorly installed concrete steps were poured against the siding 25 years ago.
    The front is pretty straight forward, however the back, under sliding glass door is rotted from stem wall to subfloor. I’m more concerned about supporting that whole corner to prevent injury and more damage.

  17. Hi Ken-

    Thanks for your comments. Yeah, working on a corner is way harder. You may want to consult with a structural engineer on how best to support it. My best guess is that you would have to support both sides of the corner by inserting a beam across (sort of like forming a triangle), which means you would have to punch through at least one exterior wall.

    If I had to work on a corner, I think I would hire a professional (and make sure that they have an active liability insurance).

    Let me know how it turns out


  18. Exactly the information I was looking for! I’m going to do a similar job today. A previous landlord put a patch on a termite problem after taking care of the termites. The patch is failing and now I’ll be replacing the rim, sill, and several joist. Thank you for documenting how you did this. The pictures will be most helpful.

    Eric Cross

  19. This is a great article. Thank you. I have a rotted rim joist between the first and second floors of my house. There used to be a veranda attached to the house there. When the previous owners removed the veranda, they just covered over the header with some cladding, and it has been rotting ever since. The rim joist is about five inches thick. The exterior 2 inches is mostly rotten. The interior three inches is still good wood. I plan to chisel out a cavity, smooth the bumps with some epoxy paste, and then insert planks to create a glulam inside the old beam. Removing the beam entirely would probably cost me more than I paid for the house! Either side of the rotted section, the wood appears pretty good still. I plan to cut into this about 30cm to provide a safe margin.
    Thank you again.

  20. Hi Tony-

    Sorry for the late response! As you may be aware, its been crazy with COVID-19 stuff.

    Glad it worked out for you. Please stay safe


  21. Thank you for this very specific snd informational series. I found an almost identical situation under my front door last week. I am no longer a DIYer at my age but I want to know what a job entails. Then I can determine how honest a contractor is with me. As a woman, honesty has not been a forthright quality I have found in the contractors in the past. So all the knowledge and information I can gather is helpful. Thank you

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