Reinforcing Floor Joists - Pro Tips

REPAIRING A BOUNCY FLOOR BY SISTERING JOISTS
Disclaimer: www.aconcordcarpenter.com/dis...
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A client recently asked us if we could reduce the “bounce feeling” in their bedroom floor.
Sistering | Doubling the Joists can solve a lot of problems like sagging, uneven, or strengthening undersized floor joists. Sistering adds structural integrity to damaged joists and can also be used to level old floors.
2-Methods of Sistering
Full length sistering is the strongest method, and my preferred method when possible. This method extends the entire length of the joist and has full bearing support at each end. This method requires a minimum of 1-1/2” to 3 inches bearing at each end.
An alternative to bearing is to install joist hangers from a wall or supported blocking.
Mending Plate or Scabbing:
In some remodeling situations, it is too difficult or impossible to get a sistered joist onto a bearing point. I find that in these situations using a mending plate or plywood scabs can help tremendously. A mending plate is typically a 2x joist section fastened to the old section of joist to strengthen it.
There are 2 rules of thumb when installing mending plates:
1. Install the sistered mending joist ⅔ the length of the original joist, this can also be used to fix joist sag.
2. Extend your repair 3 feet on either side of a damaged area. This method reinforces the damaged area, and the joist ends will be able to handle the additional weight of the sister.
“Plywood scabbing” is also an effective technique that allows you to add strength to and fix minor problems that are affecting floor joists. I often use construction adhesive and 8D ring shank nails or structural screws to fasten 3/4-inch plywood as scabs to both sides. When scabbing I try to use the full 8-foot rip of plywood or the longest length that will fit.
8 Steps on Sistering the Entire Floor
1. Remove Plumbing, Wiring, Cross-Bracing and Other Obstructions
First step is to remove any blocking, wiring, plumbing, or HVAC in your way.
2. Measure and Cut the New Joist
If you are running the sistered joist the same length as the old joist, use that joists measurement. If you are sistering a partial joist, use the ⅔ rule if possible.
Pro Tip:
To ease fitting, we cut a 20-degree bevel of the top edge of the joist [1/2’ in and ½” down] this helps the joist slide past the subfloor and into place.
Ensure your new joist has at least 1-1/2” to 3’ of bearing.
3. Install The Joist
Slide the new joist “crown up,” into the space and tilt it up. The goal is to ensure the sistered joist sits snugly against the old joist. If the old joist has sagged, you may have difficulty getting a full-sized sister joist to fit.
If you cannot fit the sistered joist against the old due sagging, you can jack up the old joist to create room.
Pro Tip:
If installing a partial joist, you’ll also need to jack up the old joist to level and then sister the repair to that.
4. Jacking
I position a 6-ton hydraulic jack under the old joist and on top of a board spanning several floor joists. This support board helps spread the downward pressure weight of the jack to the floor below. I fasten two 2×4’s together to make a simple jack post. I then slowly jack the sag out of the old joist in order to get the new joist against the old joist. Jacking too fast can cause wall cracks above and it’s always best to jack slowly and not too much.
After lifting the cracked joist, I used a 3-pound hammer to move the new joist into position.
5. Level Vs Flat
Level is not always achieved but certainly desired. Flat is usually the consolation prize to level, in old houses. We used a combination of strings, levels, and a rotary laser to attempt to get the bottoms of our new joists level. We consider all of this information and raise or lower the jack post as needed. We also sometimes trim the joist bearing edge to assist in in fitment.
6. Fastening
To attach the new joist to the older one, we installed a series of 3-inch Fasten Master Head-LOK structural lag screws in a “W” pattern. Once secured, we released the jack pressure and remove the jack.
7. Install Solid Blocking
The last step is to install solid blocking perpendicular to the joists. Solid blocking helps to transfer weight to adjacent joists. We snap a midspan line, cut our blocks a hair stronger acts as stronger than the space, and tap them in with a hammer.
Install the blocking in a straight ling [not alternating] for the strongest connection.
8. Strap The Ceiling
The last step is to install 1x3 ceiling strapping 16” on-center to the ceiling joists. Strapping is fastened with two 8D ring-shank nails per joist. It seems that strapping is an N.E. kind of thing, but I like it for two reasons.
1. Strapping can be easily shimmed to level out the ceiling
2. Electrical wiring can easily be snaked in the ¾” space for future wiring running, like adding recessed lighting
#FloorRepair #ReinforcingFloorJoist #LevelingFloors #SisteringFloors

[@duanecartwright971]

Somebody give this man an award for effective communication. Explaining succinctly is a real talent and this guy has it..

[@ConcordCarpenter]

Thx

[@hotmetalslugs]

At the same time, he is incapable of returning emails about a simple job. Weird phenomenon.

[@sinclairamissah7006]

@@hotmetalslugs😂😂😂

[@inverness2323]

Holy cow! Best KZbin instructional ever made! Every question I had about my 1930s floor joist was answered in 11 minutes. Brilliant.

[@jamesfargo8574]

This video is incredible, the best ceiling reinforcement video I've ever seen. Every homeowner in America would benefit from taking 12 minutes to watch this instead of the crap on TV. Excellent information, to the point, and very clear with helpful video examples and demonstrations. Thank you sir, keep up the good work!

[@ConcordCarpenter]

Thx

[@donaldshimkus539]

Sorry, but not every homeowner would benefit from this video. Most homeowners don't give a rats ass about how their house was built OR how to fix a problem. They only know how to poke buttons and toss money at it. I grew up in the trades and enjoy working on my house.

[@Mike-qo4kp]

If this content was on cable TV I might actually watch it

[@miked8227]

I had to work on my back in a tight crawl space for about four days re-enforcing a floor. Cutting full length sisters was not an option do to the tight confines. I was not able to get a full length ridged board under the crawl space so I ripped 3/4 treated plywood and sandwiched the 2x10 joists, glued, screwed, and carriage bolted . It worked like a charm and stiffened the floor up like I wanted.

[@billm4212]

Great tip on the 25 degree bevel. Thanks, Rob…

[@bryanherman1035]

As an electrician that does all manner of home remodeling/repairs/additions, fishing wires without strapping is nearly impossible without doing some kind of damage to finished ceilings. There is simply no way to gain access or fish a wire anywhere that is useful. I install tons of wafer lights in existing homes, and with strapping, I can put them just about anywhere.

[@wdnspoon]

Ah I was wondering on that. A 3/4" centre-bore won't weaken the joist, but you'll need to cut the full length of drywall to run new cable. Strapping would be a nice straight channel you could easily fish through, and wafer lights don't even need you to mount a box.

[@ts109]

You can jack a joist by getting rid of the jack, and just making the strong back longer than the distance you need, a block between it and the temporary support plank on the floor can help it slide along. then just tap it into place with a sledge hammer. Unless you are lifting tons of weight it will go real easy, and you can be very precise. This saves the risk of kick back with the jack.

[@melmartinez7002]

I'm in the process of sistering / scabbing a first-floor - which means I'm in the crawlspace and also dealing with the entire weight of both stories instead of just the 2nd floor. This video was useful - especially the tip about beveling a corner off the sisters to make it easier to hammer them into place. Wish I'd thought of that earlier. A tip not mentioned is that an oscillating tool with a tungsten blade (get a 3-pack) is extremely useful for quickly dealing with bazillions of existing nails and staples sticking through the subfloor and mis-nailed & sticking out of the existing joists. You want to cut those off so they don't interfere with the placement of the sister joists AND to save your head from getting poked in the brain while crawling around with your head up between the joists and under the subfloor.

[@jamesbowenjr.3022]

Liked the part on strapping the ceiling for future wiring. Never gave that a thought. 👍

[@mariopanteli7924]

I've recently tiled my bathroom. Room is much heavier than what it was.... I've seen no movement or damage to the joist (plasterboard is off on the ceiling downstairs)... But I've had this horrid feeling whenever I bath that I'm going to fall through the floor 😂 thanks for the vid, will be sistering the joist soon enough!

[@billj5645]

I'm a structural engineer- I watched your video because I was curious what you were doing. Most of your video seemed to be sound information. When you are strengthening a joist by adding on pieces of plywood, or even when sistering a joist you should add on pieces as long as you can make them, otherwise you can have problems where the shorter piece ends, it won't transfer its share of the bending stress back into the main joist. When you are working around plumbing penetrations you could rip the joist, put 2 notches in it, and fit one piece above the pipe and one piece below the pipe, then connect those pieces to the joist with more screws. For a notch at the top or at the bottom of a joist you would have to sister on both sides of the joist with shallower pieces. As for jacking up pieces of wood- a joist can take a permanent set over the years due to load and you may not be able to get all of that out by jacking up the joist before reinforcing it so be careful with that.

[@Billybob-go8hn]

Being a structural engineer means nothing tbh, I just had an engineer draw up a repair for a truss on the bottom chord, he has me infill, has me sister sister each side with the 2x4 extending 2 foot past the infill on each side. Nail pattern is on a zig zag every 3 inch. That’s all fine ig, then he has me rip 3 qtr plywood to sister on the top and the bottom of all that with nails on 3 inch. That was just last week, they let anyone become an engineer and half of em just make sh! t up and leave zero detail on the drawling.

[@Loonypapa]

@@Billybob-go8hn He's not just making sh- up. APA, SBCA, BCSI, MiTek, they all have design procedures for repairing wood trusses and gussets. It's not rocket science.

[@Billybob-go8hn]

@@Loonypapa you obviously have never built a house in your life. The bottom chord is pulling, why would you need to over kill with plywood on the top and bottom. I’ve dealt with engineers like this guy, I just go to another guy with some sense. Nothing in this video was done wrong, he is a book smart engineer worth nothing. I’d love to see his crappy drawlings.

[@Billybob-go8hn]

@@Loonypapa one day you’ll learn every project is different and not everything always works. That’s why engineers should have mandatory on site training.

[@billj5645]

@@Billybob-go8hn Unfortunately not all engineers are equal but I have the experience and the education to know what I'm doing.

[@robbrundrett7510]

OK, OK, OK, I'M HOOKED ON THIS CHANNEL!!!!!! ROB KNOWS HIS STUFF. I'M A 64 Y/O LANDSCAPE CONTRACTOR THATS BUILT LOTS OF THINGS AND JUST LEARN SO MUCH FROM THIS VIDEO. GOD SPEED TO YA ROB.

[@ConcordCarpenter]

Thx brother

[@ConcordCarpenter]

Wow! Thanks

[@anastasiabuss1483]

This was immensely helpful. We just bought an old farmhouse with some joists we’re concerned about. This was the most thorough and well explained video I’ve come across yet.

[@hey.you.in.the.bushes]

Great video. I probably have PTSD from that very enthusiastic presentation, but great stuff!

[@njreno1]

As a Roofing Contractor, I like to watch programs on building and carpentry so that I can see what I am missing. The grind of roofing gets old and I sometimes think to myself, hey why not build garages and work your way up to homes. Then I wake up and realize that I love the freedom of being outside and not inside my customers home. Sometimes working inside is like walking on eggshells. You guys do great work and I enjoyed the video. Looking forward to some wood slivers this summer!

[@lilcreaper007]

If you wanna mix it up id recommend get into pole barn buildings .that carpentry is outside and fun youd like it

[@turkeytrac1]

As a recently retired carpenter, it's very refreshing to see someone building to best practices, bravo!

[@levyrogers6979]

This is some of the best information on floor or ceiling repair I have heard of. Thank you from all of us DIYER. You have made our lives alot better my man. Wow!!

[@ConcordCarpenter]

Thanks Levy

[@williammorris3303]

I did a 3 story on wheeling island. 5 broken (and I mean BROKEN) floor joists serving the first floor. It had significant sag. I felt that my best option was to Jack every joist on both sides of the break , on every break, simultaneously. The sounds this house made was scary af and had the effect that I was the only one in the house soon after beginning the process. It was tough getting the new 2x12s in but it was a relief when that was done and I didn’t have the house in the basement on me

[@jncn1490]

7 1/4 lvl good choice . We would have NOT overcut the notched joist ends , better to use a jigsaw to finish that cut and not weaken the joists. Also glue the new joist to the existing. And add a rim board under the new floor joists bolted to the foundation or even better a wall on both sides if possible to carry the load , since the notch only leaves about 4” on the sill.

[@Loonypapa]

Actually the best option in this case is to fully block the stud bay and let it rest on that blocking. Especially with an LVL. LVL's require a minimum bearing area.

[@rob-toolsandtech2521]

That beveling trick is a good idea.

[@DennisMathias]

THIS is one of best presentations you've ever done.

[@lisaferrara8120]

This is vital and very helpful information! Thank you for posting this.

[@ConcordCarpenter]

Glad you like it, thanks for commenting

[@MustPassTruck]

Always fun finding what crazy past homeowners have done in old houses. Have a room in my house with the ceiling 10in joists notched down to only 4in left for an upstairs bathroom.

[@dyc9124]

classic

[@Dingo500]

The man who built my house father in law worked at the local dump, it shows...

[@jamesbailand4311]

Blocking in those notches where possible, helps.

[@donnlongstreet5110]

Amazing to see REAL CARPENTERS... love it!

[@johnberry1107]

Good stuff! I’m a DIYer mentored by generations of kin, neighbors and peers that were either raised by or lived through The Depression. You fancy. Stay safe. Water wins.

[@sheldonpearo2003]

I am a carpenter and enjoy learning new ideas to fix things. I have a open mind and always learning knew thing's

[@johnkruton9708]

A contractor tip in Fine Homebuilding magazine showed a method of jacking the floor with a 2x4 backstrap across the joists and the using jack screws at 3 even locations to provide tension and level the floor upstairs. At even space you use Simpson strapping thats 2” wide and .026” thick galvanized steel with pre drilled holes in it so you use #8 TICO nails and start at one end up joist on the side top and and the middle fold over and go up the other side to the top of the other end. Do this for 3 or 4 evenly spaced joists. He said he had excellent results and you maintain ability for lighting, insulation and other sound deadening products in between the joist bays. I”m looking at using this method to fix my bouncy upstairs floors in my 1962 split level that used bare minimum 6 x 8 joists for the span. I’ve already used 2x6 dry wood blocking method under my main bedroom over the garage with good results. The blocking is ok in the garage area as I won’t be doing any heavy soundproofing like I will in the basement. I’ve searched YT and haven’t found anyone posting up any pics or vids of this method and the results.

[@jamesrobinson1022]

Take into consideration what is above the joists also before jacking them up especially if there is floor tiling as it will crack the tiles and mortar if they aren't already which can lead to whole bathroom remodel that wasn't in the budget or time.

[@donaldshimkus539]

I lived in an old Victorian house (2nd floor) and had to put in a support beam under my dining room floor. Three 2x10s didn't do it. I wound up installing a 3/8 x 9" steel flitch plate in that beam. That took the bounce out of it.

[@waoh2010]

120ish year old house with logs for most of the framing…rot and termites have done their worst. Now I’m gathering good advice to fix my wife’s dream house. Thanks guys!

[@SJChip]

I can't imagine the number of people who will be helped by the information presented here. So many tips and rules! Worth repeated views!

[@lelandlewis7207]

My house is a balloon frame built with old barn beams by the original owner back in the '50s. The first-floor joists are 6" round "trees" flattened on the top. The centre walls weren't stacked on the main beam, so I have a major drop (2"-3") between the beam and the wall and the outside wall and inside wall because the wall is the support for the second floor. Even the openings for the basement and upstairs stairways didn't have any support or proper headers. I have wanted to redo the main floor joists for a while and this video has pretty much laid out what I had planned. The only difference is that I am going to remove the existing "trees", one at a time as I add the new joists and I will be going 16" on centre instead of the roughly 24" that is there now. The second floor is somewhat better, having old-style beams of a true 2" x 5", but they are on about 30" centres, so I will be adding new joists between them.

[@neville78]

I’m doing this with my deck, this is exactly what I needed

[@williamsmith9026]

I wish I was the painter on that job! The windows look like a good time

[@kiwdwks]

Thanks Rob. Appreciate you sharing your knowledge!

[@justgivemethetruth]

This is a great video. I've never heard anyone talk about this - and probably the reason is that it is a much bigger and more expensive job to tear up the whole floor and redo it. I think I might be able to use this at some point, and there are many great ideas here. Thank you do an honest, clear and helpful video.

[@BreakingPintMedia]

I see a lot of grateful folks in your field...but I just wanted to thank you for helping those of us > not in this field < comprehend things with your concise explanation! Our 35+- year old house was built on a Friday at 5pm and had liberal exercising of "open" spaces. Our office and one of our sitting rooms sit on top of a finished "open concept" basement and have more bounce than we can tolerate. I have been looking for such thorough explanation of the problem and what proper solutions look like.

[@DS-zf9zb]

I have been scouring the internet for direction on the best way to salvage the floor in my over 100 year old home. Your video was perfect. Thank you for sharing your knowledge!

[@eddiekamin]

Best video for sister beams on KZbin IMHO! Thank you for the information.

[@ericgjerde5376]

This is a great video, thank you so much for making this and sharing this information.

[@italianballbreaker]

New subscriber here. I recently found some damage due to water and termites. Took care of the problems but now I need to get the plywood and also the sill and joists replaced. When I have a structural engineer check it at least I have some idea of what he’s talking about. Thanx for a great video

[@josephcook4222]

You did an excellent presentation by any measure. You make sense, speak clearly and a perfect pace! Thank you. Next, Flitch plates.

[@captainkirk1745]

So glad I discovered your channel. Great information, right on time!! Many thanks!! 😄

[@wordimobi5765]

Excellent pro-tips, that sets your channel apart, many thanks.

[@TheEclecticHandyman]

I'm not a pro or even in the industry, but this was a very informative video. Nice job.

[@TheFizz263]

Very well said. Thank you for sharing.

[@Dr-wheel-barrow-opperator]

Thank you for sharing your knowledge.

[@ckcuev]

Another great video Rob. Lots of good tricks and info.

[@scottmorris4914]

Great video and good info. Have a safe trip this week.

[@miguelp4812]

Ok. That was awesome! Thank you. I'll join as soon as I can.

[@matrix64]

Excellent information and explanation! Thank you

[@MrKjm444]

Great presentation and detail for this work - thank you!

[@mattshank7524]

The single most helpful video I have ever seen on old home construction. Thank you!

[@wdnspoon]

Good and comprehensive. I'm hesitant to put in strapping, as 3/4" centre-bored joists comfortably fit 3 NM cables, keep them well clear of any future screws, and I don't believe significantly weakens the joist.

[@franbeller5897]

This is exactly the information I need. You have confirmed the method I planned on using to repair my shed floor. Thanks!

[@ArtbyPaulPetro]

this was extremely informative! thank you so much!

[@grumpyuncle.]

Awesome information. Thank you!!

[@worldofwisdom617]

Thank you fpr taking the time to do this video. Very informative and has helped me with my project.

[@weloveups831]

Great video! Everything was explained very well. You also got straight into it. Great information in a short video.

[@clutteredchicagogarage2720]

Great video. I've watched a lot of your videos, and I've been consistently impressed with how clearly you organize your content and explain the details. Also, I've seen a lot of your videos on tool reviews, which are very well done. There are a lot of people on KZbin who review tools. When I see that you also make content on how to sister joists in very old buildings when you run across all kinds of tricky site-specific situations, I can tell that you're not just a KZbin creator but also a guy who has worked for a long time as an actual carpenter who had to figure out solutions to fix issues with old homes. Great work all around. I've lived in old houses with both sagging and creaky floors, and I know that the old floor that you sistered with LVLs is going to be quiet and much more level than it was before you started. I think all the people living in that house for the next hundred years will be very happy with the results!

[@tomsoltess6636]

Great video! I use structural steel L's with carriage bolts. It retains the height of the ceiling a bit more expensive but it works.

[@saundraholmes9969]

Extremely informative to a novice! Thank you for sharing!

[@user-lk8hu2bw7x]

Rob Thank you for your detailed explaining. It helps many to understand how or why things are done a certain way. Look forward to other videos of yours. Nate

[@ByronicGuitarist]

Really informative video, super helpful for some DIY reinforcing I'm about to do in my 1950s home. You've earned a new subscriber!

[@eldergeektromeo9868]

Thanks Rob. This is a subject that is not really covered. Great Info!

[@KAKADOUJACK]

Southern Carpenter here: I've never seen that strapping technique in a ceiling, so I guess it might be a Northeastern thing! Thanks for all the very clear and straightforward tips and the excellent and extremely professional presentation.

[@ConcordCarpenter]

Yes its totally a NE thing

[@nhiakhang2622]

Very informative video. Thanks for the tips.

[@meancuisine8]

Awesome content right here!!! Thank You!

[@dubtownman9508]

Another brilliant upload..

[@lloydferguson400]

Excellent video. I did a job like this last year and I did pick up some tips that would have helped. Thanks for the video.

[@sergiovivas5401]

Good tips, quite experienced contractor, Greetings.

[@mrstogie912]

Thanks Soooo much for posting this Video!

[@romank8603]

I Always learn good stuff from your channel!!!

[@camdenchild]

Thank you this is the best video, I’ve seen in a while, I appreciate the detail

[@mostrico]

I learn something new today, thank you so much for sharing man!!

[@AlloyedFrequencies]

Thanks for explaining 👍👍

[@Jared_Albert]

Thank you very much for taking the time to share your hard earned knowledge. It’s very generous and many people benefit from it and appreciate it. I also really appreciated the slow careful explanation paired with well lit video. With my hearing difficulties I had no trouble tracking the explanation

[@willbunn9019]

This is honestly one of the most informative videos I've ever seen on KZbin to learn about something I had no freakin clue how to address. Thanks!

[@ConcordCarpenter]

Glad it helped please subscribe

[@myfixituplife]

Nice work, Rob. Great detail. Level V Flat…Always a tough choice.

[@MichaelNatrin]

Fantastic video!

[@nesteezy4884]

👏 I’m a Carpenter and do mostly concrete formwork . currently redoing my bathroom and ran into some rotted flooring and ran into your videos and will say that I love how thorough your vids are 👌 thanx for the content

[@YouOldSailorYou]

Thanks, great video! I just learned 17 new things 🤯

[@tombirmingham7354]

Thank you!

[@stevenfoust3782]

Excellent techniques!

[@bser3973]

VARY good information for my project. It's hard to get good information these days. Thank-You.

[@ruidadgmailcanada8508]

Excellent information, you know your stuff, make it easy to grasp with great demonstrations and are always recommending better than the standard minimums. Thanks from 🇨🇦

[@Nick1253]

Thanks for the vid, the loft space in my garage is sagging quite a bit and has since I've moved in.

[@BlackenedEclipse]

Very informative and useful info, after reading some of the comments it appears that’s there are many different yet effective ways to achieve the same desired outcome. Happy Building 💪🏽

[@deosiewilson732]

That was clear concise and made lots of sense to me...... Thank you for the video..... I don't have an old house but I do like to learn.... 🎉🎉

[@johngriffiths812]

Thank you for this. I've spent a few months just soaking up all the information i can about how to fix up our building. Still trying to get a structural engineer. this video helps a lot!

[@jaaches]

Great video. I'm a carpenter. Lots of useful information.

[@chubsmichaelfats]

Great video!

[@123upandadaminc8]

I know nothing about this stuff and now I'm an expert, just kidding, I really like the video👍🏼👍🏼

[@akesha4138]

This really depends upon the span length which in this video seems about maximum. Otherwise you might need to increase the board width like upgrading 2 by 8's to 2 by 10's. No one wants a center floor post. If it is in the basement however consider adding them, this increases structural integrity substantially. You might consider blocking on the ends if room permits, doing these will help improve earthquake survive ability Often in Missouri I have seen a metal I-been added later to get rid of sagging. Always make sure that the crown of the board goes UP to meet the downward force. Quality work inspires custom fitting and finished mastery, as you have done here. Also you do not have to pull all metal off the old joists, sometimes cutting them off flush works well.

[@ConcordCarpenter]

thx

[@TheSpatulaCity]

Practical tips. thanks.

[@terrygalyen5925]

Nice work. Great video all around, thank you!

[@ConcordCarpenter]

Thanks

[@craig5477]

Excellent information taken directly from experience. The info I trust always come from those who have done it and have the ability to explain it simply. If you can’t do that it means you only have a superficial understanding. So thank you for giving the direction I need to go. Cheers

[@critian19747]

thanks for your video I am planing to reinforce the floor in my house ,, very clear simple information perfect...all the best

[@danielames7611]

Great vid, bro! You are a gifted speaker, and the info is nice and dense. No fluff. Great job!

[@ConcordCarpenter]

thanks

[@Chef1Mat]

i didn't know about bevelling. great vid mate