Ok... real talk. Two questions so I know how to proceed.
1) the west wall (an exterior wall) had the most sag in the floor. I suspected termite damage from a really old infestation (none there now, and the exterminator guesses many decades old).
In this photo, you'll see what's left of a 2x4 that was nailed onto the sill and supported (somewhat oddly) with 1x down to the dirt. This was the nailer for the subfloor. On this wall, the subfloor doesn't go under the wall for some reason... maybe a slapdash repair, who knows. The foundation appears to be concrete, but can't really tell how thick. Outside is lath and stucco. The 2x8s behind the 2x4 are mostly trashed as well. Part of me is thinking that if they're trashed, they're obviously not supporting any weight, but it seems like there are 2 or 3 of them sistered in there. So the other part of me is thinking if there is just barely enough non-eaten wood left in them, maybe they are feebly supporting the wall, and removing them will cause the house to collapse with me in it. How do I proceed with this corner? Do I rip out the eaten wood and replace it? How do I know what is supporting the wall without taking these out to see?
2) The joists on this side of the room are spaced at a frustrating 18-20". Fine for 1x6 boards, not so great for 4x8 sheets. I could cut all the floor sheathing to a lenght that matches the spacing, but that would make one continuous seam in the middle of the room. I could add one joist at 8' from one of the walls, but that would also make a seam the whole way across. I could add TWO joists; one 8' from the left wall and one 8' from the right wall so I could stagger the sheathing. What's the "right" way to do it?
In reply to Curtis73 (Forum Supporter) :
Kinda hard to tell from pics but to me that looks like a lot of dry rot.
Is the stucco cracked on the outside? Stucco is very heavy and cement in general is brittle so if it isn't cracked, my guess is it's being held up. Or they did the stucco after the fact and it hasn't moved anymore than it's going to but that seems less likely
Definitely not dry rot. 100% termite. When you pull it apart it's full of sawdust and very specific tunnels. Also tunnels leading to and from damaged areas of the wood.
The more I look at the inside/outside, I don't think it is a concrete foundation. I think I'm looking squarely at just the stucco because I can see the lath in places on the inside. What the picture also doesn't show is that the outside was covered with T&G 1x6 as the sheathing... which is also gone. So, from inside to out, it appears to be the 2x8s, then the 1x T&G sheathing, then lath and stucco. I think the foundation for this room (which is an addition) is two 2x8s sitting on those concrete blocks in the corners.
Stucco on the outside is a little cracked, but not in the area where the most sagging is. Inside there is a crack in the concrete/stucco/whatever over near the sagging, but I don't see that it has moved. It's not as if the concrete broke and sunk, there is just a crack.
Also forgot to mention in the video, this entire rim joist is just dust. It's a double 2x8 and both of them I can peel off with my fingers.
I also did some measuring in the framework of one of those little basement windows. The stucco is attached to what looks like basically a half inch backer board. The concrete is not the foundation.
Yeah that's definitely lathe and stucco that is brought all the way down to the ground. Usually you don't want to do that because it wicks up moisture.
Really everything looks like a loss that I see. I'd probably dig in a footing and do like a pressure treated pony wall all the way around to hold up the house because what's holding it up is definitely on it's last legs. Block or concrete would be better but heavily built pressure treated pony wall would work too and it gives you a level platform to put your new floor on. It's also a bit more user friendly then block.
How do I get it under the wall though? I'm afraid if I take out that wasted lumber, it might be just enough to have the wall come down on me.
I'm calling the insurance company tomorrow. I've never done a homeowner claim but they might want to chip in to prevent bigger losses down the road. You know, collapsed wall, injured homeowner, dead dog, that sort of thing. :)
And thank you all for the information. I can build darn near anything, but I'm not sure I'm up to this learning curve.
Also just learned I set my homeowner deductible to $2000. That was dumb.
Curtis73 (Forum Supporter) said:
How do I get it under the wall though? I'm afraid if I take out that wasted lumber, it might be just enough to have the wall come down on me.
I'm calling the insurance company tomorrow. I've never done a homeowner claim but they might want to chip in to prevent bigger losses down the road. You know, collapsed wall, injured homeowner, dead dog, that sort of thing. :)
After you do the concrete footing, you can either crib up what's left of the structure or even put in some 6x6 posts and build your pony walls around it. It might require a lot of corrective brute force carpentry though too
Maybe I'm not asking the right question. The double 2x8 rim joists are toast. They are what is collapsing. I don't know if you can see that one hole in the rim joist... that was from my thumb. It's mostly hollow. If I pour concrete and put a wall under the damaged rim, I'm not correcting anything. I need to remove the rim joists and build a wall under the sills of the wall but I'm not confident the wall will remain upright if I do that.
Curtis73 (Forum Supporter) said:
And thank you all for the information. I can build darn near anything, but I'm not sure I'm up to this learning curve.
Also just learned I set my homeowner deductible to $2000. That was dumb.
No problem, repair like this kinda sucks no matter where you are on the curve rrally
Curtis73 (Forum Supporter) said:
Maybe I'm not asking the right question. The double 2x8 rim joists are toast. They are what is collapsing. I don't know if you can see that one hole in the rim joist... that was from my thumb. It's mostly hollow. If I pour concrete and put a wall under the damaged rim, I'm not correcting anything. I need to remove the rim joists and build a wall under the sills of the wall but I'm not confident the wall will remain upright if I do that.
What I would do is sister onto the rim and build up the existing structure so you can build the pony wall underneath.
Let me look at the video again in a sec ( I'm at dinner) but I think you can just sister onto the existing , put it on the corner block and put it underneath the other wall to hold up everything. This will hold it up while you get the pony wall built
I wouldn't remove the old rims at all, it'll eventually rot away but it won't matter because it's basically doing nothing but for now it's all that's holding the building up in it's current configuration
Thanks for the picture. Totally makes sense.
I know that I personally don't feel up to digging around a foundation and then putting a wall beside or under a rotten rim. Having never done anything like this before, I don't want to cross my fingers and then do something dumb.
I think my plan of attack is to call insurance first. If they say it's covered, great. Let someone else with better insurance collapse the house. 
If they say it's not covered, if making a claim isn't financially wise, maybe I'll try to find a friend of a friend who does this sort of thing and offer them some money to help me out. I just feel like I need a wee bit of hands-on guidance.
Your idea totally makes sense and I appreciate it. I have a feeling I'll call someone and they'll describe exactly what you suggested.
I'll draw a quickie of what I think it looks like, which is darn near identical to yours except the placement of the rim under the wall.
As you can see, any pony wall that goes under is going to support nothing but wasted wood. That is to say, it won't prevent further sagging. I thought I had to get to the wall/sill for support.
Were it me. I would through bolt a couple of 2x8s( SYP floor joists) to the wall over the rotten doubled rim joist. Then jack that wall up and clear out the rot and replace said rim joists. I may be mistaken but I think its a single story stick framed house so its not really a lot of weight.
A couple of notes on through bolting. Remove the sheetrock 4' or less to expose the studs. when lifting a wall this way you are only lifting what ever has a bolt in it so bolt every stud you want to move. Once you've jacked the wall up put a couple of studs cut to length under the through bolted joists.
The bottom plate of the walls probably are a bit rotten so with the sheetrock out of the way you'll have access to fix that too.
Use pressure treated lumber for anything that touches the ground or concrete.
Rinse and repeat for the next rotten rim
Don't do anything that you feel uncomfortable with. Structural repair by its nature seems kinda sketchy. Attempt at your own risk.
It is a 1-story stick-built house. Outside of this corner is an eave and roof. What if I don't lift. Can I support it like the picture below?
I'll try to explain. The corner in question is about 1" lower than the rest of the floor. Since I've already lowered the rest of the floor 1/2" to get to my target framing height, that means that corner is only 1/2" lower than I want. So, in this picture, the yellow is 2x6 that is screwed through the drywall to a stud using multiple HeadLok screws (basically really expensive 3/8" lags). The red are bottle jacks. From there I could:
A) jack it up enough to support but not move the wall. Then replace bad wood with PT in the original location (1/2" low) and notch/shim as necessary. Replace span joists 1/2" too low and then shim everything up to my target height. This sounds like a recipe for a weaker and noisier subfloor.
B) Same as A, but when I install the span joists, I notch the ends so I can install them 1/2" higher than the rim to get my target height.
C) Actually raise the wall 1/2" and install the rims 1/2" higher to match my target height.
My hair-brained idea was leaving the double-layer drywall on to keep as much rigidity in the wall as possible. I believe the outside sheathing is likely 1x6 or 1x4 T&G. Let me know if this picture will kill me quickly, or slowly and painfully.... or if it would be fine.
I can't see the picture. It sounds like you've lagged into the wall in question,this will probably work,the sheetrock is only minimally doing anything so lag a stud or 2 across that wall if you're worried(3points in a plane for triangulation). You don't have to lift the wall at all, if you like where it is, some clearance maybe helpful however. I like the sound of option b. I have done similar things before with good results
I've also made a decision that I should bounce off of you folks.
The left wall in the picture is a single rim joist with minimal damage, but some. This means I think I will leave that old rim in there and sandwich a new PT rim against it because I can slide it under that sill without removing any structure (other than the span joists). At least on that wall, I have the space under the sill plate to add, and an existing rim joist that will still hold a screw in most places.
The right wall in the picture is a double rim joist with extensive damage. That's the one that really needs all new lumber.
So, from that picture, can I just throw a support on the right wall, tear out the old, replace with new, and maybe add a paver with a 4x4 post under the middle? Or maybe dig down 6" or so and fill with a bag of concrete to make a pad for a 4x4?
That would probably work. My instinct is to try and catch more of the wall so I would attach the 2x6 horizontally as opposed to vertically. I'd say you are on the right track.
Ok.... one more question before I feel almost confident enough to start tearing E36 M3 up...
Are the span joists integral to the integrity of the house. If I remove them all, will I risk the base of the walls falling in/out? Like ceiling joists hold the tops of the walls together, are the joists responsible for holding the bottoms together?
For the left wall, should I take out the first half of the joists, install a 6' piece of PT (resting on that block you see under the window, then replace with new spans before tearing out the rest? Or should I rip them all out and put a full 12' piece across and not worry about it?
I tend to replace as I go. i.e. first i would support the walls then replace the doubled rim joist,then tackle the single rim on the left. I would probably double it up. one half then the next half then a full length rim. the span joist aren't really attached to anything currently so I would doubt they are holding the bottom of the wall in place. Provided the walls are mostly plumb it shouldn't be a worry. gravity works in a straight line. If you're concerned you could temp a board between the existing floor and the bottom plate of the wall in question. You could also temp some diagonal braces on the side walls. if its a worry go crazy with bracing and temp walls. if you have good instincts use them to prevent being squashed if you don't, brace the e36 m3 out of it.
use a ledger or joist hangers to attach the span joists on the outside rim.
