Engineered Joist To "pocket" Into Masonry Wall?

 
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Old 12-12-2008, 06:53 PM   #1
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Engineered Joist To "pocket" Into Masonry Wall?


Does anyone have any recommendations for the treatment opf an existing double wythe masonry wall when it comes to them housing a TJI or engineered lumber joist? I have done this with new construction, but never an existin wall. I assume just custom form some grout pockets into the existing pockets that will be left after we remove the existing joists, but I thought someone here would have actual experience with having doen that. Maybe someone could shed some light for me?

Thanks
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Old 12-13-2008, 08:31 AM   #2
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Re: Engineered Joist To "pocket" Into Masonry Wall?


We do that all the time. We go at least 3-1/2 inches into the masonry (CMU usually), making the pocket hole wide enough (16 inches) at first to allow access to fill the voids in back and beneath as far as we can, and wide enough that we can swing the beam in, and deep enough that we've got a 1/2" gap between the end of the beam and the back of the pocket, but making sure at least 3 inches of the end of the beam is seated. We install a 1/2" steel base plate, as wide as our rough pocket, over mortar for the seat. In goes the beam, and we level with steel shim plates. We fill in the voids on either side with brick and mortar, leaving 1/2 inch space between beam and adjacent brick/mortar.

It's also important to properly assess the existing wall. You might need a pilaster to carry additional weight, and if the wall is an old cinder block wall a new pocket won't fly without reinforcement. That's why it's always a good idea to have an engineer in your network. Give him a call and run it by him. I don't mind taking calls like that from the guys I know. If the inspector needs a sealed sketch of it, it can be done on an 8.5x11 piece of paper in short order. I'm actually doing one today for an historic building here in my neck of the woods. Not masonry, though. Trying to adapt an up-to-code fire escape egress to 120 year old wood framing requires expertise.

Wait a minute. You're an architect? You really should know this. Ching 4th Edition, man. You really, really should have an engineer in your network.


Last edited by Aggie67; 12-13-2008 at 08:43 AM.
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Old 12-13-2008, 07:41 PM   #3
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Re: Engineered Joist To "pocket" Into Masonry Wall?


Well thanks for the reply Aggie, that is great confirmation of what I was leaning toward ...

As far as the last part of the statement ... if you can find me a design professional that knows everything, or never need ask for input, then I will show you a world where builders aren't ever pissed of at said individual and where jobs never get screwed up.

We have an engineer in the loop, I wanted builder input though, which you have given me in detail. I appreciate that.

Thanks much
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Old 12-13-2008, 08:15 PM   #4
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Re: Engineered Joist To "pocket" Into Masonry Wall?


Consider this next job:LVL's and I-joists have been around long enough, and installed badly enough that I've seen a few getting bad at the pockets. The cmu's or solid pours are like sponge rocks, carrying moisture up through capillary action, or osmosis, or whatever it is that makes them like the "quicker picker-upper." Also, the thin (like no R value) masonry at the back of the pocket is a perpetual dew point due to moist basement air and temperature differentials. I have my students line the pocket with a lowly plastic milk jug with handle side and top cut off. An extra wrap may be duct taped in place for additional height. After the floor system is finished, we use closed-cell foam to seal the entire end, totally divorcing the girder from the masonry and eliminating the temperature/dew point issue. And, yes, keep the 1/2" end clearance for foam.
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Old 12-13-2008, 08:45 PM   #5
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Re: Engineered Joist To "pocket" Into Masonry Wall?


You're right about the moisture issue. Especially here in Chicago.
I have usually just called for the pockets to be sealed. Temperature will still be altered by the weather at various points of the truss's chord, but the moisture will occur next to the pocket, instead of in it.

Not sure I follow your Duct Tape reference though, what do you mean?
Do you think that will fly with Chicago Building Code? LOL jk ;D
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Old 12-13-2008, 09:05 PM   #6
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Re: Engineered Joist To "pocket" Into Masonry Wall?


Untreated lumber should not be in direct contact with masonry. Joists need a fire cut when placed within pockets. This prevents the joists from acting as levers if they were to collapse during a fire and overturn the wall above those pockets. if you are concerned with lateral stability of I joists placed loosely in pockets consider bridging or blocking those joists adjacent to the wall between bays. i would never ever consider buttering up or filling pockets with mortar or concrete. As an architect you really should know this.

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Old 12-13-2008, 10:53 PM   #7
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Re: Engineered Joist To "pocket" Into Masonry Wall?


Quote:
Originally Posted by umop-3p!sdn View Post
You're right about the moisture issue. Especially here in Chicago.
I have usually just called for the pockets to be sealed. Temperature will still be altered by the weather at various points of the truss's chord, but the moisture will occur next to the pocket, instead of in it.

Not sure I follow your Duct Tape reference though, what do you mean?
Do you think that will fly with Chicago Building Code? LOL jk ;D
I just meant that the second milk jug section is usually needed to provide a tall enough total barrier, duct tape holding in position until foamed.


Last edited by critter; 12-13-2008 at 10:58 PM.
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