Rim Joist – cut out rot, replace with good wood and then double up floor joists
Hi,
Ranch/1 story house sits on a crawl space about 3′ high. The backyard was improperly graded so that the dirt went above the concrete foundation and onto the boards of the house. As a result, rot came into play.
I’ve had the grade fixed and the dirt removed. I now have full access to the rim joist on the outside. It’s about 2x9x25 (yes actual 2×9″) – it’s 2 lengths meaning it’s a 12′ and a 13′. The floor joists run towards this rotten plate so this wall is load bearing, the floor joist ends nail into this rim joist.
In the corner of the house, where the downspout was, there’s significant rot of the sill plate, the rim joist and three of the floor joists.
The sill plate I believe was a 2×5 (yes, actual 2×5 – I think the contractor had custom lumber cut).
Here’s the condition of the corner.
There’s no sill plate for about 6 feet. The rest of the sill plate is rotten about an inch or two in. It runs the whole span of 25 feet.
The rim joist has about 6 feet that has about 2 to 4 inches rotten away. As a result, I have a nice hole showing into the crawl space.
Three of the floor joists are rotten about 2 to 3 inches. They are angled rot meaning the top of the floor joist is fine. It’s just this “triangle” of rot. More rot facing the rim joist on the bottom, less as you go into the crawl space. The floor joist has about 2 to 3″ of good wood sitting over the existing foundation wall. It would sit over the sill plate but…well, that’s gone.
I need a reality check – here’s what I’m thinking of doing.
1) Knock in 2×4’s underneath all of the “non-rotten/affected” floor joists from inside. The foundation wall is 8″ thick. I have a 2×5 sill plate. I can fit in a 2×4 PT easily. This will help give the non rotten joists lots of sill plate upon which they can sit.
2) Pull out/cut out the remaining rot from the outside facing portion of the 25′ of sill plate. Measure the space and then push in another 2×4 ripped down to a good width. This will give me the 2×4 inside, some of the original non-rotten sill plate and then the new stuff I just jammed in there.
3) Cut out the rot of the rim joist and replace it with new wood.
4) Put in a 2×8 over the area that has “no” sill plate, put the existing floor joists down on that (i’ll jack up the house a bit so I can fit the 2×8 in there) and then sister on 2x9x6′ joists next to the original floor joists so that the three floor joists that have rot have 2 to 3″ of their own coverage on the sill plate while the sistered in floor joists have all 8″ of space. I’ll bolt these floor joists on too – say every 12 inches off set.
I don’t want to have to run a whole new floor joist in there. I want to just strengthen the existing floor joists.
Is my thinking correct here? Do I really need to run in full 2×9 floor joists because only say 3″ of the original floor joist will sit on the sill plate?
Thoughts?
Inside the crawl space, 3 of the 2×9 floor joists show signs of rot. I’d say 2 to 3″ of three of the floor joists are rotten. But there’s still about 2 to 3″ that sits over the foundation wall.
What I have now is an opening that’s about 2 to 4″ in height, maybe 4 to 5 feet in length that allows one to literally look right into the crawl space.
I pulled away the siding so that I have full access to the whole rim joist. I can see that only 4 to 5′ of rimjoist is rotten and it’s not the full height of the 9″.
The sill plate…ah that’s in trouble. Almost the whole 25′ of the sill plate is rotten at least an inch or so in. It’s hard to tell how deep the damage is. The sill plate looks to be a 2×5 (odd dimensions to the lumber in this house). As a result in the crawlspace there’s about 3″ if space between the block foundation wall and the floor joists. I was able to knock in 2×4’s (pressure treated) to many of the existing floor joists where there is no “hole”. This means that most of the floor joists are now sitting on PT 2×4’s and all of the 2×4.
So questions.
1) Can I just remove the rot from the existing sill plates, then knock in another trimmed down 2×4, caulk it up and i”m good? I’m thinking yes because I have the 2×4’s already there. So now I’m doubling up the width of the sill plates.
2) The section with the hole all the way through and the floor joists that have the 2 to 3 inches rotten off, can I put in a 2×8 sill plate, have the remaining 2 to 3″ of the non-rotten part rest on top of the new 2×8 and then sister in 2×9’s to the floor joists? And when I say sister in, I’m thinking put in say a 6′ section with bolts on either side?
When I’m done, all of the floor joists will have at least a new 2×4 plus new 2x something under them. The 3 floor joists that have the tips of rot will have at least 2″ on the new sill plate and then the sistered joist will rest completely on the 2×8.
Thoughts? I hope I explained this properly. When I’m done, everything will have some coverage on the new sill plate. The three floor joists though will gain strength from the sistered joists. Key is if I have put on enough.
Thanks everyone.
Replies
You have no idea what you're doing. Hire a competent carpenter or contractor.
Agree and get a permit.
Don't need a permit for repairs in many states. Contractor friend showed up, patted me on the shoulder, said I did a good job.
Define "competent." Around here, most "professionals" would do far less repair than is proposed in this post, especially to a light-framed ranch.
If I were doing this work for you, I'd be very tempted to raise all the joists just enough to go ahead and remove the entire sill plate, replacing it with a treated 2x6 or 2x8, and replace the entire rim joist. If you have a block foundation, be sure to raise the joists rather than trying to drive the sill into place, as you may knock the blocks loose. You'll also need to check for anchor bolts in the old sill. If there are bolts, you can notch the new sill where needed to slip it into place. I also think you'd be totally fine to sister the ends of the compromised joists as you proposed. Unless they're under a heavy load, they'll be fine.
As for your 2x9's, they might truly be an odd dimension, but I have come across 2x10's from the 60's that measured 1-9/16" x 9-1/16"
Hi - thanks! That makes sense. I have not found any sill bolts which I found odd. So either they are spaced well beyond 4' or there aren't any.
Good point on knocking in the 2x4's.
My biggest problem is that contractors in my area are booked out till January/February with my favorite contractor being booked out until March. I live in a hot construction market - Upstate NY.
My second problem was finding lifts/jacks. I was able to find 1 50ton lift. That worked to get the floor up. I am spending the next few days bringing it up a little bit at a time. But then this morning it was 31 degrees so lots of now I have a race before we get more cold nights. It's drafty in there.
Thanks again for actually reading and providing feedback. Chat soon!
I’d say go for it. Your fave contractor may be willing to field questions or even come by for a consult. I’m always buried in work, and if someone has thought things through and is willing and able to tackle something of this nature, I’ll advise.
Not surprised about the anchor bolts if the home is older. Even houses in California weren’t built with em for a long time. Frankly, with a block foundation, the bolts don’t add much structurally unless the blocks have been reinforced with concrete fill and rebar pins driven down into the footings. As far as I know, you’re in a low-risk zone for seismic and tornadic activity, but you should verify local codes for a retrofit situation and decide from there.
As for jacking the floor, I raised our entire house off the foundation to level it using one 20-ton and one 6-ton bottle jack and cribbing. I often raise floors with a jack and then drive props in under the joists to move the jack to the next lifting spot. Lay a 2x8 or 2x10 on the crawl floor parallel to the foundation and use it as your base for jacking and propping. Once you’ve lifted enough, lay a chunk of 2x material on the 2x10 with grain perpendicular and then drive a 2x4 prop in under the joist. A sledgehammer is very helpful rather than your 16-ounce nailbeater.
Hope this is clear enough. Good luck
You are saving a contractor a lot of trouble, and yourself a lot of money. Plus, a new war story to tell.
Done this exact job 3 times this year. I prefer to raise the floor joist with a temporary beam just enough to remove the sill and rim. Slide in new floor joist from the outside, replace rim and sill then wrb and flashing. Not a job for the faint of heart tho. Cost my customers in the 2-5k range with a lot of blocking, jacks, and comfort with crawling around in the crawl space. Don’t skimp on this project and do it so you’ll never have to do it again.
Thanks for these kind words. I was successful with the 50 ton jack. That thing was so heavy...jesus. But it worked. Second time I do this, it will go faster.
I'm sorry, I do think you need to have this looked at by an experienced carpenter or contractor, but I should have been more polite in my response.
Standard lumber sizes have changed over time. Long ago, 2x8s were actually two inches by eight inches. Now they're 1.5 by 7.25. In your situation, rot and moisture have affected the dimensions, so it's not likely it was custom cut.
Beyond that, rotten sections of sills should be completely replaced - scratching out just enough of a rotten sill to pound in a piece of 2x4 doesn't count. Likewise, rim joists are a major part of the support of a house, so don't make small patches - replace at least four feet. Floor joists can be left in place if the rotten section is cut out and a new, full length joist is sistered to them.
Take my advice with a grain of salt. I'm not an architect, engineer or code inspector.
Yes. Essentially I did what you and others have highlighted.
I removed appx 20' of sill plate. I replaced with 2x4's initially in the back and then with the house jacked up - 2x6's in the front. The combined sill plate is now a 2x10. There's overhang inside the crawlspace. The floor joists are now fully resting on the full width of the crawlspace wall block where as before they were only on 4".
The rim joist has also been fully replaced. And the three floor joists that had rot at the tips now have new 2x9 7' sistered with bolts spaced every 12 to 18". In the case of the three floor joists with tip rot, there was about 3" of good wood still on the end. This means that the existing floor joists and the sistered floor joist are sitting on the new 2x10 sill plate.
Most likely this is okay for the next 10 years.
We come to this forum because we need help/advice - not a driveby "get a professional". Thanks for returning with actual advice. Have a great rest of 2020.