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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!


Tuesday 31st of May 2022

Excellent series of articles. Well done.

Courtesy of the hindsight you gave us (without having to actually do the job!), was there any need to compress the sill seal, before adding the top sill plate? Could that have allowed it to fit (without notching)?


Monday 4th of April 2022

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


Thursday 20th of February 2020

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.


Monday 18th of May 2020

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


Eric Cross

Monday 24th of April 2017

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


Wednesday 26th of April 2017

@ Eric-

Awesome. Good luck with your project!


Ken Lane

Thursday 19th of January 2017

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.


Friday 20th of January 2017

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