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Leveling subfloor for hardwood

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curtis73

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Oh... another important thing to note that may be of importance. This is a one-story house, so directly above this corner is an eave and roof. Not trying to lift or support a 3 story house or anything.
 

bud16415

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My first question is what is above? Truss roof / framed roof? Second story then roof?



Second question is can you removing some siding and make these replacements from outside? Jack on inside replace from outside or the other way around.



I am not a pro and have been hoping some others would feel free to jump in with their 2 cents as well.



IMO lifting in just 2 lines against 2 studs and under 2 joists would not be enough removing long sections of the rim. I especially think it is not enough after knowing the same guy that built the floor most likely built all above.



I would be looking at removing the wall coverings about a foot up and then attaching a high temp rim joist to each stud connecting it all at the bottom and strong enough to lift against and block while getting the rotten stuff out. Opening the wall would also show you if the damage extends up into the studs where they may need to be trimmed off and maybe even a taller replacement rim be installed.

Even if it is only a single story there is a huge amount of weight not being supported by much now and it has to be held solid wile you get something new and strong in there.
 

mabloodhound

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Jack as Bud shows and replace a piece at a time (5' / 6' or so). If there are multiple thicknesses, make sure you stagger the joints at least 1 foot. Of course do one wall at a time. And put some vapor poly down over that dirt before you cover it up.
 

curtis73

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There is some poly down there, I just moved some of it out of the way. They didn't do a good job of coverage which I will correct, but vapor barrier is definitely on the list.

I actually have a clear shot to do both as a single piece, so I'd like to do that. Based on all of your advices, here's my plan.

Today I dug a hole near the stucco. It's about 9x24 x 1 foot deep. I mixed up 80 lbs of concrete and filled it, then embedded/leveled a 4x8x16 concrete block in it. There wasn't a support pier in the middle of this wall before, so probably not necessary, but it will make me feel comfy with a 4x4 between concrete and the new joists.

I also got an endoscope in between the sill and drywall by cutting a wee bit off the bottom. The bottom of the sill has some termite damage for about 2' but no damage on the top of the sill and only one stud shows about 2" of damage. Poked things with a screwdriver on the studs and sill and I'm satisfied that it stays. I also poked the double rim and found zero wood. It is all toast. This means I feel that the wall is mostly supporting itself, so I'm planning to throw a 2x8-12 on the wall like bud said. I already filled/bled my bottle jacks. All I will need is modest support (he says hopefully)

Starting with the right wall, I'll support, yank the bad wood, replace with double 2x8 PT spaced up on the existing block in the corner, sitting on the concrete slab on the other side, and then (once that concrete pier I added cures) a 4x4 post in the middle. At least I know that what I'm doing will be stronger than original.

Then the left wall will be rinse and repeat.

One concern. Once I remove the old span joists, how much risk is there of the south wall falling in or out? Like how ceiling joists are what hold the top of the walls together, how much are the floor joists responsible for holding the bottoms in place? I checked and the wall is plumb, but how gentle do I need to be with it? I'm thinking about hammering in the new joists in tight areas and nailing/screwing the joist hangers.
 

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curtis73

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And the roof is a simple hip. No trusses, just some rough cut 2x from the fascia up to a ridge beam, roof is slats of 1x. Typical early 1900s construction.
 

bud16415

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The only thing I might do different with jacking .5-1.0” is I would work both walls at the same time. Less chance of breaking drywall and decoupling along roof line etc.

Maybe @mabloodhound can comment on that as well.
 

curtis73

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I've decided to play it safe on the jacking part. I'm only going to use the jacks to support instead of raise. I may lift 1/16" or so just to give me space to slide the new PT in. My main reason for doing this is to level the floor which I can do by installing the span joists 1/2" higher on the rim.

At this point, my big goal is to just have it not fall on my head while I pull the bad wood out.
 

mabloodhound

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Yes, that is a good plan. I only do one wall at a time when doing this type of work. You probably will find the new lumber is narrower than what was used so it should fit fine and may even require some shimming.
 

curtis73

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Well, the old 2x8s have... um.... compressed as they decayed. But they have a little shimming under them. I think I have plenty of space if I support and remove it all.

Should I worry about the wall after the span joists are out? How much are they responsible for keeping the bottom of the wall from falling in/out? Or can I remove the spans and not worry about it?
 

bud16415

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Sounds like a plan to me as well. I don’t think you will have any problem removing the bad joists one or two at a time.

Your project is a great example of repairing this type of damage and hope you keep posting pics as you go. It seems to pop up every year or so and it will be nice to have a (how to) thread to point to.
 

mabloodhound

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If you remove the joists, do so after getting the jacks in place. The gable end wall wouldn't be a problem but the sidewall might if you try and jack it after the joists are out. You could take a measurement from a fixed beam and check it every so often to make sure the wall doesn't move. It's only going to be a couple of days wile you replace the sill and put new joists in.
And as far as the plywood subfloor, cut the first panel to fit the longest space (less than 8') and then cut the next panel to fit approx. half the distance so your joints are staggered.
 

curtis73

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Ok, thank you. The floor joists run parallel with the peak of the roof, so (in the picture) the right wall is under the eave and the left wall is under the gable. That makes me feel better about taking out all the span joists so I can do one solid piece of rim.

The subfloor is Advantech which is an engineered OSB-style stuff. Since the room is 11'6" wide, I will simply install joists at 16" OC from the east wall, then measure out 8' from the west wall and add another joist. That way I can stagger the full sheets and minimize cuts
 

curtis73

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Ok, here we go. Today was the first real day of work. It was really the first day I had help available, and I also wanted to give the concrete I poured a few days to get a little stronger before putting weight on it. A genuine and hearty thank you for all the guidance.

Step 1: Screw 2x8 to the east wall through the studs. Used two 8 ton jacks to just support the weight. Remove bad double rim joist. This photo shows the old stuff gone. The first (outer) new 2x8 is in place. It went in as two pieces supported by my new concrete pier in the center.

1598056990239.png

Step 2: After shimming up the ends to proper height, the jacks were removed and a one-piece second 2x8 was added and shimmed up to match, then screwed together with HeadLoks every 8" or so. My buddy went a little overkill on the screws, but I didn't care a bit. Here is the second rim, installed, and being sistered to the first.

1598057210112.png

Step 3: Moved the jack sill over to the south wall and supported that wall. Cut out the span joists. After getting the joists off and cutting the nails flush, I realized that this rim was more solid than I anticipated. The last foot or so in the corner was junk, as was a very small section in the middle. I made the decision to leave it there and just add a second PT rim on the inside.

1598057446152.png

Here it is with the new rim (in two pieces) installed on the south wall. Foundation repair done, and in the process (even though it wasn't my intent) we somehow ended up gaining our 1/2" elevation in the process... at least it appears as though that is the case. I'll know for sure when I get my nailer joist attached to the east wall and I can get an accurate measurement.

1598057688837.png

So, the whole thing has now had all the bad wood removed and replaced with all new PT. The south wall which was a single rim is now a double rim. Anything touching concrete is now PT. No one died, the walls didn't collapse, no drywall cracks, and I may have accidentally raised and trued the sills in the process. I really don't know if I did it "right," but I know what I did is strong like bull. Tomorrow I need to get more KD 2x8 for span joists and install them, then I should be ready for shimming and subfloor.

1598057888605.png
 
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curtis73

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This whole process (today's foundation repair) took 4.5 hours. Materials list for this project so far:
3@ 2x8-12 PT.
1@ 2x8-12 KD for the support screwed to the studs
1@ 4x4-8 PT to make piers
5@ 12x12 pavers as mobile jack pads.
3@ 4x8x16 concrete blocks as mobile jack pads. Note: As you'll see in my pictures, I put the jacks directly on the concrete because quick calculations suggested I wasn't actually handling a lot of weight. For serious jobs, use a scrap of ply or 2x between the jack and concrete. The hard steel of the jack against the hard concrete can cause the concrete to break.
1@ 80 lb bag of concrete.
1@ mixing tub (already had)
2@ 8 ton bottle jacks and 1@ 2 ton bottle jack. (already had these) The 8 ton jacks were for the main wall support. The 2 ton with it's tiny profile was used to make sure the new rim joists were up nice and snug against the sills for shimming.
1@ box of 2-7/8" HeadLok screws.
1@ PT fence picket and 1@ PT lattice strip. These were what I cut and used for shims/spacers.
 

bud16415

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Great job! Both of making the repairs and also documenting the process. :thumb:

I can't wait to see that DIY hardwood down.

You will enjoy your floor so much more knowing all is good below it.
 

curtis73

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At this point, I don't really expect replies. This is the boring part. I'm mostly documenting stuff just in case anyone needs a reference, but if you see me doing something wrong, please chime in.

Taking my sweet time... partly because I want this just right, but also because I've been working alone for the last two days. With the exception of a couple ups and downs in the lumber, the entire framing is within 1/16" of an inch. That is to say, the ends and the center are all perfect within 1/16" of level. I will follow up with sliding a 6' level across the joists and a shim as a feeler to identify lows and highs. Anything more than about 3/32" will get shimmed unless it is just over a small area. Trying to avoid having to use anything between the subfloor and the flooring.

Notice the one joist that isn't at 16" OC? That's my solution to the odd width of the room. It's 138" wide, so if I just pulled off one wall and did 16" OC, I would have to have a continuous seam following the joist that is at 96". Since I want to stagger, I simply moved that joist 6" over. That means I have one span of 10" and the next is 22". This makes it so that I'm not exceeding a max span of 24", but it also puts a joist in the right spot for when I start with a full sheet on the left. My urge to do things beefy might win, and I might put an extra joist in the larger span that is in the middle, but so far this is all complete overkill. I'm trying to tell myself "I don't need that joist, so why add something else that might need shims and leveling?" As it is, I could space them all at 24", remove that center support, and still be at 135 psi shear.

On the right wall you'll probably also see a 2x6 that is spaced out with some 1x scraps every 2' or so. This is because the original sill had fallen about 1/2", so spacing it out gave me the ability to put a nailer rim at the right height. I did regain about 1/8" when I did my jacking and replaced the rims, but not enough.

foundation7.jpg
 

curtis73

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So, I re-mathed and decided that everything on 16" centers would only cause me to buy one more sheet of subfloor, so I took changed my mind. Everything is 16" OC now.

I traced over the joists with the 4' level and didn't see any dips or rises that really needed my attention. Nothing more than 1/16" or so.

Made a lot of progress today. My buddy stopped over again and we were able to finish the joists and lay about 80% of the floor. I even put new register boxes on the ducting (I kinda mangled the old ones getting them out). The bonus is, I turned on the laser and measured in about 15 completely random places, and every time I got exactly 18-7/16" That floor is level and flat, baby.
 

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