Our basement remodel calls for removing a support beam from under the first floor joists (to bring the ceiling height to code). In order to support the increased floor span, the engineer calls for sistering the joists, and adding an additional joist between each pair (changing the joists from 24″ on center to 12″ on center).
My question: Is construction adhesive sufficient between the new joists and the subfloor? If not, how do I avoid removing the hardwood flooring on the floor above in order to nail into the new joists? (The subfloor is 3/4″ T&G and the hardwood is 3/4″ maple.) Can I toenail from below through the joists into the subfloor?
Thanks for any hints on this.
Replies
I think if you try to toe nail upward, somethings goign to go wrong and you're goiung to screw up the hardwood.
I also don't think you need anything more than good adhesive. You will need to block and bridge between the old and new joists to keep them in place.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Kreg jig it??? + adhesive of course. any reason that would be bad?
I think this would be a perfect application for pocket screws. They'd just have to remember to drill the holes before placing the joists.
i do not think you need to attach the new joists to the subfloor. they need to be attached to the old joist so the two act as one. Not sure if adhesive is good enough by itself. why not nail them to each other?
why not nail them to each other?
Because they will be 12" apart. he is adding new joists halfway between the existing ones to reduce the joist spacing."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
a compressor and a plam nailer could do the job with ease and it would be done right...
I think you're talking about the joists to be sistered & Eddie is talking about the new joists to be added half way between the old joists (not sistered to anything).
You are right i did not pick up on the original post that it is a combo of sistering and adding in between. With that in mind I there is no structural reason I can think of for adding joist in between unless the floor above is deflecting between the joist? If the issue is to increase the joist span only then you should be able to sister all the new joists to the existing joist and not have to fasten the existing subfloor/ finish floor to the new joists.
In that case a palm nailer and 16 penny nails would still feel like the best solution. The thought of all the added work to fasten the floor to the joist from below, in a narrow space, when it adds no strictural value does not feel worth the trouble.
"there is no structural reason I can think of for adding joist in between unless the floor above is deflecting between the joist?"I can think of several structural reasons, first is that the engineer said it was necessary, and he knows the other details that you do not. What qualifications do you have to undo his work especially without knowing the pertinent details?second, the whole floor system is being re-engineered, NOT simply the floor joists.third, my experience with similar situations makes me wonder if even adding this much more joisting is sufficient.
My preference would be to design and insert a flush set beam rather than removing it entirely.
But I'm not the HO, the contractor, nor the engineer on this one.
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Because the engineer said it is not a "strucutural reason" it is a direction given by the engineer. The reason behind the direction needs to be determined. Thus the question could be asked to see if there is an alternate way to achieve the required reinforcement.
I have not and did not "undo" anything the engineer required. I like most who post to this site have stated an opinion based my understanding of the original post. Any change should be reviewed with the engineer and i was remiss in not mentioning that.
As to my quals i have been a licensed architect for 25 plus years and as such have done the engineering for this type of structural change before. In addition i have hired engineers to make help me make this type change.
According to the original post the span of the floor joists is being increased. This to be done by adding joists that have been engineered for when the original beam is removed. I understand that the entire floor system is being redesigned.
There has been no discussion about the joist size i assumed the engineer specified a joist size based on his calcs. Assuming the existing beam is at midspan, if the joist depth did not increase significantly then i would question the engineering also.
There are always a number of ways to solve any problem and i agree with you about using the flush beam.
Engineers and architects often to not take into account the means and methods of construction when they come up with their solutions. Their expertise is not in means and methods. Thus it never hurts to ask about alternative constuction methods to achieve the same solution.
Assuming the subfloor and finish floor are not deflecting to much with the existing joist spacing then there may not be a strucutral requirement for spacing the joists at 12" oc. When you do the calcs, assuming a regular spacing, it is the number of joists in the floor system that is important.
Thanks for introducing yourself tho. Such a background may help add credence to your advice in the future. Glad to know your statement before was not as careless as it first sounded.but"When you do the calcs, assuming a regular spacing, it is the number of joists in the floor system that is important."I'm not sure what you mean by 'regular spacing'
Does that mean 16" OC
or does it mean the same spacing at every joist, whether 14", 12", 16" 19.2" or 24" Having done all the above variations regularly, buit knowing that a lot of guy7s un-used to engineered floor trusses might only consider stick framing 16"OC to be regular, I am left without understanding what yuou mean.But with either interpretation, I come up short of agreeing with the rest of that final statement since depth of joist hast much to do with engineering a floor system - at least as much, if not more than, the number of joists.
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Any spacing of those spacings could be used. What should not be done is a irregular or random spacing. All wood floors are designed based on some spacing of the floor joists that is consistant so that all of the floor joist share the load equally.
The depth of the floor joists is critical to the strengh of floor system. it has been a long time since school so do not qoute me on this. If you double the span of a beam (ie the joists) then i think the moment (stress?) increases by a factor of 4. The result is that in a floor system the stiffness of the floor has to increase by a factor of 4 when the span is increased by a factor of 2.
The stiffness of a given structural member also increase exponentially as it depth increases. So a single 2"x12" is stronger than say 2-2"x6".
If it was me i would be sistering the new joists and holding the new joist down from the subfloor above. As long as the new joists do not touch the subfloor there will be no "squeaking" issues to worry about.
I see where you are going nowSo if the original engineer's calcs showed that to use the same size joist depth, while doubling the span, the number of joists used needed to triple, then to keep even space for consistantcy of loading and total overall performance, then it is better to add the two for one new joists as sisters to each side of the existing, rather than adding one sister and one intermediate joist at 12", as long as the floor has no deflection.Good point about dropping the new sisters an inch and avoiding contact with the subfloor!
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If the new joist is shaved a little thinner, does it actually add any strength to the existing joist if it is not well fastened t the existing one? Point being, just sistering a new shorter joist and using a half dozen nails to hold it in place won't add much strength."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Not sure what you mean or why raise that Q since nobody is advocating doing a halfazzed job like that.
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Ok, if the new joist is full height and full length, it carries part of the load. If it is not as tall, and is sistered to the old joist, it will add strength to the old joist on ly if it is properly fastened together. Woodhak mentioned sistering a shorter joist, I justr wanted to point out to the OP that it's not as simple as fastening it in place with half a dozen nails.
"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Edited 8/5/2009 7:44 pm ET by FastEddie
"Woodhak mentioned sistering a shorter joist"I didn't see that.
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If it was me i would be sistering the new joists and holding the new joist down from the subfloor above. As long as the new joists do not touch the subfloor there will be no "squeaking" issues to worry about.
Post 28. "shorter" referring to the height. "Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Strange terminology there.Shorter is how long I cut the darn thing end to end.
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I agree, I hesitated when tyoping it. How would you describe a joist that was not as tall? Opposite of tall is short, opposite of long is short."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Smaller or less depthBut we aren't talking about one that is not as tall. Same size, but set lower in elevation.
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If the new joist rests on the same bearing, then it has to be planed or ripped 1/4" narrower so it doesn't contact the flooring above."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
No - it can be relieved or notched at that seat
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Ouch. Missed that.
But you know what this reminds me of? Prior disciussions about adding steel flitch plates between two wood memebers, and Art getting into the detailed explanation about the required bolt pattern which always takes the DIY by surprise cuz they didn't realize how much detail was involved."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
What about using dimensional lumber for the sistering and TJI's for the new joists.
Could you then lay a nice bead of PL on the top and screw up threw the flange into the subfloor.
Not reccommending this method, just brainstorming.
Just for discussion, yes, you could get them in that way.But moist times I've been retrofitting joists like this, I have needed to cut the seats a bit to get them in. you can't muddle with the chords on I-joists though.and I'd hate to have to run engineering on a mixed system like that
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I assumed the added joists need to be just as long as the original joists. They should sit on the same plate as the original joists. The idea was not to rip 1/2" from the entire length of the joist. If the joists sits on a plate then notch the ends of the joist the same depth as the plate and say a 1/4 to 1/2 inch. Then the new joist will sit below the sub floor and eliminate any squeaking issues. This will also help with the clearance need to roll the new joist upright next the the old joist.
You are correct they need to be fasten together to work. The new joists need to be nailed to the old joist in the with more than a half dozen nails!! If the nail pattern was not specified than I would think 3 nails 31/2" commons every 12". No reason to skimp on nails.
From what I'm reading, you are removing the beam which the floor joists are supported by. If that's the case, none of this will do anything unless that support is replaced in some way.I would follow the engineer's direction, but the sistered joists should be fastened to each other, by nails or bolts, which may be easiest, drilling the holes with a 90deg. head. But we're ALL guessing, since this is an important issue with such a sketchy description of what you are actually doing. A picture's worth 1000 blogs.With all due respect,
Bobalu
With no connection between joists and subfloor, there will be squeaks and edit - yes, you missed half the joists by just thinking of the sistered ones and not the interspaced at 12" OC
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Edited 8/2/2009 2:48 pm ET by Piffin
I've done it with just glue before.
No call back. I dont love it but it has worked for me.
Gotta work fast, as you dont want the glue skimming over and you cant have people walking above till the next day imho.
Wear eye protection. A big glob of glue in the eye is often a trip to the dr.
It will be messy trying to get glue and then joist and then probably more glue.
I've never seen an engineer spec something like this without including the methods of attachment. you should have him finish his job.
IMO, PL premium is fine for the joist to plywood part. sisters will need more.
Are there fasteners from the hardwood projecting thru the subfloor? if so, You are going to be using a grinder and will need to have a fire suppressor of some sort nearby.
What sort of joists do you have?
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Might be a perfect application for a concealed-deck mounting system, like: http://www.suredrive.com/Videos/ShadoeTrackInstallationVideo.htm
View Image
or
http://www.grabberman.com/Deckmaster/
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Nail to top of joists, install joists, screw to subfloor from underneath - you'll have to watch the screw length since you're going into subfloor rather than 1 1/2" (exterior) decking.
Jeff
Edited 8/2/2009 9:21 pm ET by Jeff_Clarke
I would glue it heavily and use the Kreg pocket screws.
kreg screws don't like torque...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
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"Some days it's just not worth chewing through the restraints"
kreg screws don't like torque...
okay, what about Jeffs idea? or, let the PL dry a day or two and come back and "cinch" with the kregs????
gots no idea, just askin.
PL and ring shanks for the sistering...
on the toe nailing....
PL and head down to yur favorite hardware (not a BB either) supplier and spec out fasteners in lieu of the kregs......
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Edited 8/3/2009 3:00 am by IMERC
Thank you Mr. Merc. now plz, it's late, go to bed :)
it's only 01:11...
and please....
no Mr....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Can you use angle iron with holes? Before you put the joists in screw the angle iron to thew top of the joists and then screw threw the angle iron into the bottom of the decking.
http://www.nd.edu/~me463a26/Docs/PDF%20Parts/angle%20iron%20with%20holes.pdf
use a 2x instead...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
I still don't see a reason for fastening the new joists to the bottom of subfloor other than stopping squeaks. Hardware at the ends like normal hangers does the job of holding things up, and glue stops the sque3aks of wood/wood at the subfloor. All this other is just making more work with no gain as far as I can tell.
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believe the OP wanted to mechanically fasten to the sub floor...
PL alone would work for me...
just offering alternatives...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Thanks for your input. This was the method the engineer originally spec'd, but it seems way labor- and parts-intensive. I think I'm moving toward adhesive plus "toe-screwing" into the subfloor. The engineer sort of ok'd that, but he didn't seem thrilled. I'm thinking of McFeeley decking screws which have 13/16th inch of threadless shank -- self drilling and no pre-drilled clearance hole required. Does anyone have experience with that method or thoughts on it? Thanks to all you who have replied. Your input has been helpful.
I would be inclined to sister on two 2xs of about half the depth of the existing joists, so that the bottoms are even, and then glue/screw plywood onto the bottom of the composite joists. This would make a very stiff torsion box out of the entire floor.
The pieces sistered onto the joists, shouldn't need to go all the way to the ends of the existing joists. At the ends where the joists connect they are under shear, and most probably are strong enough to resist that loading. You need to build them up on the bottom portion of the half in the middle, starting at the quarter points, so that you are increasing the ability to resist moment, which is seen in the joist as tension stress on the bottom.
"The pieces sistered onto the joists, shouldn't need to go all the way to the ends of the existing joists. At the ends where the joists connect they are under shear..."I had that thought and almost said so, but by removing that center beam, there is a lot more load being adding to the ends of those joists - how much I don't know but enough to require tripling the number of joists.I agree you are 'probably' right, but....?
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