I'm working on repairing subfloor and have to sister up wood to the existing joists to provide support to the patched portion of floor - this is right around a door.

I measured the existing joists - roughly, and they were bigger than 8", so they are 2x10s. Off I go to the hardware store and get a bunch of 2x10s. I understand that 2xwhatever is usually 1.5xsomething less, but I thought they were all standard.

My floor joists measure out at 9" (checked in my work area plus other unfinished areas in my basement), whereas the new 2x10s I bought are 9.25". What gives?

The newly purchased 2x10s are the proper dimension. Are you only patching subfloor? If so, why are you sistering in full 2x10s?

Could be due to age of those floor joists. Also could be due to some "builder" using a private lumber company and have them cut to size, to save wood.

Two solutions, in my view. One just use the new 9.25 inch boards.

Lumber companies used to cut the boards from logs at just over 2 inches for thickness, and just over 10 inches for width. Etc for other sizes. Since then they have been doing the rough cutting smaller, and smaller. That way they get more boards out of a log.

They used to cut 2x4s out of regular logs. Now many of them are cut out of scrub pine that are barely big enough. We end up with the center pith in every 2/4 cut that way. Equates to more money for the lumber outfits.

Several decades ago my dad and I built our own house. 2x4s actually measured 2x4 inches, and were planed on all 4 sides. Same for all dimensioned lumber.

How old is the house?

They’re most likely 2x10s. When initially cut to size, wood studs are usually at a certain moisture content. After being in place in controlled humidity conditions, the moisture content often drops, causing the wood to shrink. New members sistered with existing members are one place where this change often becomes quite obvious.

I had to sister up joists for a customer. They were 2x6 floor joists. Same thing different sizes. I had to notch them by about 1/4 inch. Not ideal but better now.
I have to believe that the original wood shrank a bit.

quote:

Originally posted by a1abdj:
The newly purchased 2x10s are the proper dimension. Are you only patching subfloor? If so, why are you sistering in full 2x10s?

This ^^^^^

I'm leery whenever I see/hear "sistering" mentioned. Often it's done entirely incorrectly.

As for dimensional lumber sizes: Nominal Lumber Size Dimensions and Conversion Chart

Are the joists damaged/rotted? If not, just use some 2x4's as nailers into the sides of the joists to secure the new subfloor to.

When I was much younger and learning a little carpentry from (old School) my dad and great gramps that was called a scab and deeply scorned.
However for small non load bearing areas, can be ok and save from a much larger job.

Around here older construction, pre WW2 or so, used a lot of locally cut hardwood timber that could be about any dimension within reason.
"Factory" cut and planed lumber cut to standard dimension is very uniform, but the standard has changed over the years. You could be looking at two different generations of standards. ie; 2x4 changed from 1 3/4 x 3 3/4 to 1 1/2 x 3 1/2

quote:

Originally posted by ensigmatic:
I'm leery whenever I see/hear "sistering" mentioned. Often it's done entirely incorrectly.

Would you point us to the correct method, please? Thank you.

I am repairing subfloor right at my back door. the joists run parallel to the door. The joist I am sistering to is right up against the outer crappy plasticy coated fiber board sheathing under my siding. There is some wood rot which I will stabilize and fill in - about 3/4 deep for about 4 inches.

That joist is right under the outside edge of the door frame. I need to provide support to the subfloor patch. To provide that support, I need to come away from the original joist at the outside edge of the door frame, three board widths to have enough edge exposed from the inner edge of the door frame for the patch to sit on.

I've seen how people use 2x4s on joists to provide support, but I have to come out far enough from the original joist that I think there will be too much torque on it from the weight from the subfloor (or rather a fat guy - me, standing on that part of the subfloor).

In my mind, I sister up 3 2x10s, sitting right on top of the sill plate (same as the original joist) and I can park a truck on that part of the floor - the load from the floor patch will go straight down through the innermost 2x10 onto the sill plate. This appeals to my sense of "why build when you can overbuild?"

The other alternative which makes the fix look like the original install, is to jam subfloor under the door frame to sit on top of the original joist. I'm not inclined to do this because then I can't get at the subfloor to glue and screw that piece down to the joist (because of the existing door frame). I'd rather leave it to the Andersen people coming later this month when they rip out the door - they can put in a patch and screw/glue/waterproof the sh!t out of that part when everything is opened up.

So, the sistering I'm doing is less about supporting the original joist, which is still sound, and more about supporting the subfloor patch so that weight is pushed down in the sill plate instead of torquing the original joist.

I'm going to shave down the 2x10s to match the existing joists.

If there's a downside to my plan, please advise.

Wait until they have the door out or take the door out now and do the repair. Removing the door is really an easy task. With the door out secure a piece of treated 2x10 roughly a couple feet longer than the doorway or the damaged section to the present joist. Use glue and long screws. Do the same to the joist where the repair section will end. You may want to add a piece of 2x10 to either side of the repaired section. Like making a box for the new piece of floor to sit on.

quote:

Originally posted by vthoky:

quote:

Originally posted by ensigmatic:
I'm leery whenever I see/hear "sistering" mentioned. Often it's done entirely incorrectly.

Would you point us to the correct method, please? Thank you.

There is no "one correct method." It's dependent upon what's being done.

RobLew, I'm confused It sounds like what you're trying to reinforce is the load-bearing edge of a rim joist, maybe?

quote:

Originally posted by Captain Morgan:
I had to sister up joists for a customer. They were 2x6 floor joists. Same thing different sizes. I had to notch them by about 1/4 inch. Not ideal but better now.
I have to believe that the original wood shrank a bit.

2x6 floor joists? Even on a short span that is undersized for a home interior.

quote:

Originally posted by RobLew:
My floor joists measure out at 9" (checked in my work area plus other unfinished areas in my basement), whereas the new 2x10s I bought are 9.25". What gives?

99% chance that your home is old enough the wood has had time to shrink. It's not uncommon to have to rip new wood to fit it in with old.

If the house was older, you could have rough sawn "full boards, which would actually measure about 1-3/4" now. The Olde 2x10s I come across typically go 9-3/4" by 1-3/4," 2x4s in older homes measure 1-3/4"or 5/8, by 3-3/4" or so.

Wood does shrink over time from drying out, and being compressed under load.

From the sound of what you're doing, you don't need 3 2x10s. Perhaps one added one, and a 2x4 on the side of that for added surface area. Actual pictures would help a lot.

I'd be more concerned about the source of any rotting you find, and instead of just replacing wood, finding the source of the leak. Wet or dry rot?

Arc,

I'll try to get some snaps posted to illustrate what I'm going for.

As far as source of rot - it's definitely wet rot. Lots of moisture in there that wasn't obvious from the top. It was from by soon to be replaced leaky door frame. I let it go, not realizing how bad it was.

I've opened up the floor and dried out all the wood with a header set on low. Water spots all gone now. Wood seems OK after some cleaning and a scrub down with some bleach/water solution.

OK here are some pics.

First a wide view of door and what I've ripped out and cleaned up. It was pretty wet and there was black mold in there when I opened it up. Heater over a couple of days and a week open seems to have dried things up nicely. What looks like mud on some parts of the wood is...actually mud. There are parts of my basement that had red Virginia clay splattered all over - this was one such section.
The joist is sitting on the sill plates on top of my basement wall. On the other side of the joist is the outside. Joist is at outside edge of door frame.


Close up of left side of door where most of leakage was coming from and resultant rot. I'll be using the Albatron wood repair kit to hit the upper edge of that joist. I'll put a new chunk of 2x4 to replace the rotted out wall bottom plate. Between the top of the joist and the door frame, there was 3/4" OSB subfloor. I hogged out the stuff that was rotted, leaving a gap between the top of the joist and door frame.


Here's a shot stacking two sections of 2x4 against the joist. Only a tiny lip to support the new subfloor. That's why I'm thinking of putting a third layer there. I don't want to put 3x 2x4s to build out because the weight from the patch will twist them down. I guess I could do two 2x10s with a 2x4 on the outside?


So this is what I'm dealing with. Any advice on how to approach this project more efficiently is appreciated.

quote:

Originally posted by bigmule:
Oh boy!
Does that door have an overhang?
That looks like a bad flash job.hard to tell tho..
How's that sheet rock feeling? Soft?
Do you dare open the walls MORE to look?
And they are frenchy doors..!

Also you my try to resize those pics.
Some good member input maybe lost due to slow download speed.

I unscrewed the images. (grumble) Thought I sized them correctly the first time.

Door has no overhang on the outside. In fact, I'm worried that the outside steps that were installed while I was on deployment may be contributing...

I cut out stuff till wood felt solid again. Sheetrock seems OK even after poking around. I believe the major contributor is the door frame that had deteriorated and was letting water get in.

quote:

Wait until they have the door out or take the door out now and do the repair.

I'm going to agree with this advice after seeing the pics. With the door frame in the condition it's in, you're likely to have rot to the subfloor that's still beneath it.

If it were me, I would run a 2x6 cleat all the way down that opening. That will catch your replacement floor where it will meet the wall, and give you a bit more support beneath the new doors. Should be easy enough to do that and any other prep work now, and then cut a replacement piece of floor and set it aside. Would take less than 10 minutes to rip out what's beneath the door when they pull it and slap your new piece in place.

quote:

Originally posted by RobLew:
cause the weight from the patch will twist them down. I guess I could do two 2x10s with a 2x4 on the outside?

You could go 2x10,2x8,2x4. I like Ledgerloks for this type of thing, don't just nail or screw.

As others have mentioned, there should be flashing visible in your pics, and there appears to be none. So, any leaking will continue to occur. To be corrected it's removing the whole door unit, and exterior case, hopefully there is tar paper or home wrap to connect to under that.

There should be a pan and side flashing, your home looks modern enough that it should be a peel and stick rubber/tar product. There are lots of ways to do it.

Without this flashing, and if there is no roof over the door, any rain on the siding can get indoors, certainly wind driven rain can go right past the exterior trim.

As far as replacing part of a damaged stud, you'll want to remove enough so that the pieces you put back aren't fragile lil baby pieces, and also stagger the heights so you can secure them easily with that KJJ.

Is there a vapor barrier in there somewhere? I see what might be some 6mil, but if it's just unfaced loose in wall cavities.. oi.

Arc, you are correct. The 2x6 are undersized. Many of the home in NJ around lakes and rivers were summer vacation homes and not built for year round habitation. Over time people slowly converted them to full time living. Repairs are difficult on everything. Electric is the worst because of hidden junction boxes in the walls.

Apologies for the thread drift.

I would remove the door and jamb. Add a joist under the door. Even if you have to rip it to the same width allowing it to rest on the plate. Use the ledgerlocks like Arc said. I would add pieces of 2x10 perpendicular to the joists further locking it in place.
When you get to the point where you add the membrane, staple it so it stays put while you put the door in.