Thread: Floor Joist Replacement Project Advice

Hi - have a problem with 3 adjacent floor joists, 2 x 10 x 16, under shower area and over a crawl space that I could use some expert advice on.They were poorly "fixed" maybe 20 years ago with short sisters and the shower pan continued to leak since that time. The foundation is the raised perimeter type, with some single concrete piers in mid-runs. The main part of the house is 30' wide, with a solid raised pier running the total length of the middle. The bath is on an outer wall, so the damage is closer to that side than to the middle. Due to all the plumbing, AC, and electric and AV wiring, space is tight. Also, one joist is notched out about 1/2 of its depth to pass a waste pipe.

I've leveled foundations in a couple of houses, and replaced joists in a shed, but have not had to jack up anything beyond level that had hardwood floors to worry about. The new wood I've looked at is #2 kiln dried southern yellow pine from Home Depot. Looks pretty good. If needed, could dress the sub floor side edge to keep things level.

Here's what I'm thinking I should do, but I'd sure appreciate any advice you have.

1. Replace the joists instead of sistering to the old ones, because there's not enough space to do it. Do them one at a time, as a precaution
2. Remove the x-bracing
3. At the edge of the house, the shower wall, the hall wall and the middle raised pier, jack up the joists on the outsides from the three to be replaced. Use a 20 ton bottle jacks to raise them about 3/8" and cut 4 x 4's to hold them in place
4. Take out the blocking
5. Put some temporary blocking in at the sill for cribbing, if needed. I figure that the distance from the opposite corners of the width of a 2 x 10 is 1/4" > than the actual board width. I'm assuming that will provide enough clearance to cut the old joist out and swing the new one up and in (and beating the hell out of it with a heavy hammer.)
6. I'm assuming that temporarily raising a section of the floor 3/8" isn't enough to damage the oak on top. Actually, the only visible affected floor area is the hallway (see photo) that runs right down the middle of the house, over top of the middle raised pier.
7. Cut the old joist up in sections and pry them from the sill plates and sub floor. Cut all the sub floor nails sticking out.
8. Lay the new joist in on its side , overlapping the sill plate same as the old joist, and hammer it in to vertical position. Toenail to sill with three 8's.
9. Repeat for other 2 joists.
10. Re-install blocking
11. Lower sub floor
12. Go upstairs and check floor with level and, with a wood block and heavy hammer, pop back into place, if necessary.
13. Toenail joist tops into sub floor every 2' up one side and stagger back down the other side
14. Re-install x-bracing.

Other item: For the joist with the huge plumbing notch, use the old piece as a pattern to notch out the new one. Install a permanent jack post under the notch. I've seen various strengthening tips for big notches, like either side 3/4" plywood patches glued and screwed on. Is this necessary with the post?. The old notched joist has held for about 90 years, but it's real wood. Also need to take out 3/8" of mud wall under sink & toilet pipes so I don't break 'em.

Anything I'm missing on here? My hope is to put in a permanent fix that will pass inspection someday when I sell this place.

Thanks for your help,
Ben

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I believe in my contributions to this Fine Homebuilding discussion:

http://forums.finehomebuilding.com/b...c-floor-joists

Associated writing:
http://energyconservationhowto.blogs...ic-floors.html

Copy from that blog post:
This post was imagined, in dealing with structural analysis of composite beams, as presented in another public forum I have joined, DIY Chatroom:
http://www.diychatroom.com/f19/strengthen-ceiling-joist-151512/#post1046734

Perhaps readers here will see value in composite beam construction, and might comment. I think floor reinforcement by "sistering" has no validity, where added lumber couples that found, with rotational freedom and unlikely bearing on supports below.

I wish for academic and professional comment. Lacking that, I can attempt my own defense. The ultimate would be deflection testing of sample beams, which is within my capability, but would best happen with support of an interested college or university. For now, note that beam stiffness and strength are in linear proportion to thickness, and cubic to height. Sistering at best doubles strength. A composite 2x10 is likely at least four times stronger than a 2x6, and more than ten times stronger than a 2x4. A composite 2x12 of the same 2x lumber is strengthened by a further factor of two. What wonderful and easy control of strength! Testing and questioning are hardly justified. Does it matter that you might increase 2x4 strength by times thirty? Maybe it is just the added insulation depth that matters. Often it is sufficient to just do all that the situation allows for strength and insulation, as in availability of headroom. Sistering is best effort, only if space for making the floor thicker is absolutely unavailable.

Interest in this has appeared in a re-post to Fine HomeBuilding. I have graphics to share there, which I will copy from expansion of this post. I explain in a further example, that of the repair and strengthening of a 2x8 floor joist in my crawl space. Here is a photo.

And, here is a cross-section detail. This beam bears more load than any other in my crawl space, yet suffers a carve-out passing the bathtub drain. I go way beyond compensating for the divot. Surely the reinforced beam is as strong as a joist of 1 1/2 x 12" cross section, better strength is by the ratio (12/7.25), cubed. That is, by times 4.5.

I worried some about that beam before my remodel. I won't anymore.

My first comment is: Who to heck are some of the people making those comments?
- I only see your name here and on that DIY site, no place else.

My second comment is: You need to keep your terms not only consistent but correct - you refer to a composite beam and then label it (I presume "it" is what you are referring to) as a 2x8. A 2x8 indicates sawn lumber ... and by "composite beam" - just what type of material are you referring to: wood/plastic composite; OSB' plywood; glulam; ???; ... and using "deck screws"???

My final comment is: You need to talk to an engineer before you go about making "repairs" to other peoples houses - are you a licensed contractor?

Originally Posted by Ben Owen

Hi - have a problem with 3 adjacent floor joists, .......

Ben,
You may be on the right tack for what you want to do. BUT, you should get in a good carpenter/Contractor that has experience. Some of your basics are correct though I do think there may be a better way to approach the problem. Such as, introducing an additional beam near the repairs would reduce the dimensional size of the replacement wood needed for the span. The additional beam would also make the manipulation of the materials much easier. Yet that may not be the best approach, just an idea.

The DIY sites may give you some ideas though I personally would not suggest following their suggestions. Like I said, get in a good contractor to give you guidance. Knowing what you want to do is one thing, making it happen is something different.

Originally Posted by Phillip Norman

I believe in my contributions to this Fine Homebuilding discussion:............

Philip, glad you believe but I have my reservations. A little strange that you post floor joist in thread about attic joists and then take off on some other tangent. A little baffling.

Agreeing with Jerry that you need to specify the "composite beam", composite only means multiple materials which could be just about anything making up the composition. Just saying for future reference..


After reading through the DIY forum thread and then looking at some other threads and postings the entire site just gave me a headache. Then it occurred to me that Oregon has new Marijuana laws on recreational use. http://www.oregon.gov/olcc/marijuana/pages/default.aspx which may be what lead to "I believe in my contributions to this Fine Homebuilding discussion:..."

Thanks for all responses! Gary, the amount of rot to cut out will leave less than half of the original joist height in spots. It looks bad. When the house is sold, I’d like for this under bath area to look well maintained. This is my motivation for replacing the joists. I don’t want the inspector’s attitude to be, “boy, they let this place go.” Is that’s misguided thinking?

I was initially concerned that I could be introducing squeaky floors by cutting out the original sub floor fastening, but have realized that, besides the bath and shower floor and one half of the hallway(crosswise), the only other floor area is in a closet, and will not be walked on. The bath/shower floor will be re-tiled, so the only affected area will be the less than two feet of hallway above the 3 joists. I think I can toenail screws into this area to successfully re-anchor the materials.

I should probably talk to a hardwood floor contractor about how much jacking it can accommodate before cracking tongues, etc.

My only other concern is if a permanent jack post under the big plumbing notch will pass inspection.

Hi,

After taking out the joists, cutting the nails will be easily performed with an angle grinder and cut off blade. It will also allow for easier joist replacement as you won't have the tips snagging in the edge of the joists.

While a teleport may be sufficient to support the notched joist, the proper way to repair that is to header it off and transfer the load to where it makes sense. The better alternative is to rework the plumbing to drop below the joist then run to your stack.

The hardwood **should** typically run crosswise against the joists so raising only one side a little bit (3/8") shouldn't affect it too terribly.

Remember to get the joists in close and apply subfloor adhesive to the top edge if possible to eliminate squeaking.

Toe screwing will also be suitable however, be aware that most current subfloors are made of osb. If your place is 90 years old, it is probably 1x4/1x6 on the diagonal and that being the case, most fasteners will barely grab at all. Pl400 or similar will do a better job.

Replacing the subfloor in the bathroom with treated plywood and then sheathing with appropriate material generally will last longer as then the 3/8 plywood (tile)/3/8 particle (linoleum) will be about the only later that will rot/mold. Just be sure to use acq screws/galvanized nails to fasten with subfloor adhesive.

- - - Updated - - -

Hi,

After taking out the joists, cutting the nails will be easily performed with an angle grinder and cut off blade. It will also allow for easier joist replacement as you won't have the tips snagging in the edge of the joists.

While a teleport may be sufficient to support the notched joist, the proper way to repair that is to header it off and transfer the load to where it makes sense. The better alternative is to rework the plumbing to drop below the joist then run to your stack.

The hardwood **should** typically run crosswise against the joists so raising only one side a little bit (3/8") shouldn't affect it too terribly.

Remember to get the joists in close and apply subfloor adhesive to the top edge if possible to eliminate squeaking.

Toe screwing will also be suitable however, be aware that most current subfloors are made of osb. If your place is 90 years old, it is probably 1x4/1x6 on the diagonal and that being the case, most fasteners will barely grab at all. Pl400 or similar will do a better job.

Replacing the subfloor in the bathroom with treated plywood and then sheathing with appropriate material generally will last longer as then the 3/8 plywood (tile)/3/8 particle (linoleum) will be about the only later that will rot/mold. Just be sure to use acq screws/galvanized nails to fasten with subfloor adhesive.

- - - Updated - - -

Hi,

After taking out the joists, cutting the nails will be easily performed with an angle grinder and cut off blade. It will also allow for easier joist replacement as you won't have the tips snagging in the edge of the joists.

While a teleport may be sufficient to support the notched joist, the proper way to repair that is to header it off and transfer the load to where it makes sense. The better alternative is to rework the plumbing to drop below the joist then run to your stack.

The hardwood **should** typically run crosswise against the joists so raising only one side a little bit (3/8") shouldn't affect it too terribly.

Remember to get the joists in close and apply subfloor adhesive to the top edge if possible to eliminate squeaking.

Toe screwing will also be suitable however, be aware that most current subfloors are made of osb. If your place is 90 years old, it is probably 1x4/1x6 on the diagonal and that being the case, most fasteners will barely grab at all. Pl400 or similar will do a better job.

Replacing the subfloor in the bathroom with treated plywood and then sheathing with appropriate material generally will last longer as then the 3/8 plywood (tile)/3/8 particle (linoleum) will be about the only later that will rot/mold. Just be sure to use acq screws/galvanized nails to fasten with subfloor adhesive.

Sometimes it is easier to notch the ends of the joists so they can be rotated into place and then shim the ends. Adding a footing and post below the notch may be easier than reinforcing.

Thanks for the replies.
Tim, the toilet vent pipe may be able to be dropped down. Scouring the web, it appears to be pretty unusual to have a vent pipe coming out just below the toilet flange. I'd have to cut out the lead (straight) closet bend and replace it with a pvc sanitary T. Then add a nipple to the vent pipe in the wall and rerun the connection. I'd still have an illegal depth notch, but this time, it'd be at the bottom of the joist and would be a couple less inches deep. If I still need a permanent post, it doesn't look to me like that makes sense to do.

I do have diagonal 1x6 sub flooring. Thanks for the tip on using the PL4000. And after the rot problems from the past, you can be assured I'm going to put down a dry base to tile to.

Mark, So is notching and shimming pretty widely accepted? That would sure make installation easier. Would 1/4" steel shims be a good way to go? Guys I worked with on a leveling job one time used 'em between piers and beams.