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Hi Woodnetters
I am a long time lurker on this forum and have always found the various threads very informative. I am hoping the many people who are much smarter than I can help me figure out whether my plan is any good.
So, I am not too happy the floor in my kitchen. It is spongy and not sufficiently stiff enough. What I want to do is sister the joists in the basement. The joists are solid 2 x 8 x 10s and because of what I have to work with, I do not think I can get full 2 x 8 x 10s in there for sistering. Instead I was thinking of using 2 x 6 x 10s for sistering, and put blocking on each end where the steel I-beams support the load. Would this add any rigidity to the floor, or would it be a useless exercise? I would rather use full 2 x 8 x 10s, but that just isn't possible.
The 2nd question is what fastener should I use? Would framing nails suffice, or should I use lag bolts or something else?
Thanks in advance for any guidance you can provide.
Greg
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I would glue and screw
Make sure crown, if any, is up
I would also sister to both sides
Nothing wrong extra support....
Just my thoughts..
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08-07-2021, 05:13 PM
(This post was last modified: 08-07-2021, 05:14 PM by Splinter Puller.)
(08-07-2021, 02:36 PM)Greg in Maryland Wrote: Hi Woodnetters
I am a long time lurker on this forum and have always found the various threads very informative. I am hoping the many people who are much smarter than I can help me figure out whether my plan is any good.
So, I am not too happy the floor in my kitchen. It is spongy and not sufficiently stiff enough. What I want to do is sister the joists in the basement. The joists are solid 2 x 8 x 10s and because of what I have to work with, I do not think I can get full 2 x 8 x 10s in there for sistering. Instead I was thinking of using 2 x 6 x 10s for sistering, and put blocking on each end where the steel I-beams support the load. Would this add any rigidity to the floor, or would it be a useless exercise? I would rather use full 2 x 8 x 10s, but that just isn't possible.
The 2nd question is what fastener should I use? Would framing nails suffice, or should I use lag bolts or something else?
Thanks in advance for any guidance you can provide.
Greg
You should sister the 2x6 towards the bottom of the joists and not worry about the blocking. The floor sheathing stiffens the top of the existing joists, your 2x6 will stiffen the bottom.
Better would be to trim a 2x8 to fit. Usually you bevel the top so you can roll them into place besides the existing lumber.
Something quicker you could try would be bridging between your existing joists. They will stiffen the floor considerably. Google "floor joist bridging"
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We had the same problem: the dishes in the cabinet would rattle because the floor bounced. We put bridging between the joists. The floor in this 100-year-old house still isn’t rigid, but the dish rattling stopped.
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You can use steel strapping 14 guage if I recall. You start on one side at top end, angled down to the middle of the span, buy strapping with screw holes and screw it on to the joist every couple inches, wrap the band around to the other side and back up to the top on the opposite end.
If you can jack the joist in the middle a 1/8" before adding the strapping it works even better.
Adding 2x6 will not help much with the bounce, deflection is mostly a matter of the width of the joist, not the thickness.
As as alternative to blocking, you can run 2x4s perpendicular to the joists, 6 ft from each end, screwed in to the bottom of each joist.
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08-08-2021, 09:34 PM
(This post was last modified: 08-08-2021, 09:36 PM by Bob10.)
(08-07-2021, 02:36 PM)Greg in Maryland Wrote: Hi Woodnetters
I am a long time lurker on this forum and have always found the various threads very informative. I am hoping the many people who are much smarter than I can help me figure out whether my plan is any good.
So, I am not too happy the floor in my kitchen. It is spongy and not sufficiently stiff enough. What I want to do is sister the joists in the basement. The joists are solid 2 x 8 x 10s and because of what I have to work with, I do not think I can get full 2 x 8 x 10s in there for sistering. Instead I was thinking of using 2 x 6 x 10s for sistering, and put blocking on each end where the steel I-beams support the load. Would this add any rigidity to the floor, or would it be a useless exercise? I would rather use full 2 x 8 x 10s, but that just isn't possible.
The 2nd question is what fastener should I use? Would framing nails suffice, or should I use lag bolts or something else?
Thanks in advance for any guidance you can provide.
Greg you can probably use 2 x 8s it takes some force. I did it with 2x10 support and sistered, a jack can help depending on what's on the floor above. I had wood flooring above. The sistered in joists were laid in flat and tilted up and bolted them together. I used a really small 3/8s pneumatic drill for the holes and ratchet to tighten things up. Then again I had removed all the wiring, ducting and plumbing for the most part. If you want to stiffen it up and easily accomplished look at steel I used that for the second floor that was surprisingly 2x6 and doubling up with wood wasn't enough in some places.
Glulams might be perfect for this too. I have used them also.
placement of screws matters too.
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A Lally column works great for support and if any jacking is needed for floor leveling, support.
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get us some pics. we might be able to help ya figger out how to get 2 by 8s in there.
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I would first ask if the floor is "spongy" meaning it seems to give when you step on it. Or is it "bouncy" meaning the entire thing sort of springs.
The first would be related to the sheathing thickness and whether it is in good shape.
The second would be the floor joists and bridging would be a huge improvement.
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Yeah, I would not do sistering. A lot of work and expense, and you may not be happy with the result. I've done this on a deck and wasn't impressed.
Obviously, beam and support pole would be the best.
Distributing the load is another way. X braces, either metal strapping or wood, blocking, or even a 4x4 beam perpendicular to joists will distribute the load.
10' isn't a big span for 2x8's. What is the spacing?
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