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Old 06-16-2019, 07:39 PM   #1
Justice Contracting
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Deflection

I have a site that tile was laid knowing the support beam floated on the end for a length of 88 inches. From that beam (4x6) on side the joist run both directions for 88 inches. One side to a floating ledger board. The other side to another beam with proper support. It's been is a double 2x10. The intersecting joist on top of the beams is 2 x 8. What is the deflection rate for the floating 4 x 6 and what damage can be expected to what distance?
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Old 06-16-2019, 08:08 PM   #2
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Hi Kurtiss,

When you say “floating ledger board”; are you referring to a cantilevered section of the floor?

A sketch of the beam and joist layout would be helpful.

PS: is that a picture of the secret radiator graveyard? I always thought it was a myth!
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Old 06-16-2019, 08:15 PM   #3
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No. I mean it's a ledger board that is tied into one area that is on a foundation wall and then to the opposite side (right of the ledger board) it is tied into a rim joist that is anchored to a stine foundation. The ledger that is supporting the joist isn't attached to the foundation nor sitting on the foundation. It's framed more like a stairway opening. Whereas the joist support the ledger in between the opening. Most times there's wall beneath. In this scenario there isn't.
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Old 06-16-2019, 08:24 PM   #4
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Iíll need a sketch with layout, size and spacing of the beams and joists before I could hazard a guess of deflection. Give me your best guess on the species and quality of the wood too. Thanks!
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Old 06-16-2019, 08:31 PM   #5
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This is the best I can do without a ruler. Most of the joist are 19.2 oc but range up to 24 oc. My largest concern is that two locations that have no structural support. Specifically though that beam that floats for 6 feet or so. The one in the first two pictures
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Last edited by Tool Guy - Kg; 06-16-2019 at 08:40 PM. Reason: Rotate pic upright. :)
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Old 06-16-2019, 08:42 PM   #6
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It is my understanding that the beam that has no support for the last 6 feet has a 0/360 deflection rate and that it would cause any joist that sit on top of it to also carry a 0/360 deflection.
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Old 06-16-2019, 08:44 PM   #7
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The wood is rough cut pine from circa 1920
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Old 06-17-2019, 06:31 AM   #8
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Quote:
Originally Posted by Kurtiss
It is my understanding that the beam that has no support for the last 6 feet has a 0/360 deflection rate and that it would cause any joist that sit on top of it to also carry a 0/360 deflection.
The portion of the beam as drawn would be considered a "cantilevered" section and would provide structural support to the attached joists if properly anchored and supported on the non-cantilevered end. The exact strength and stiffness will be impossible to determine without an detailed set of measurements.

Regarding the beam you have drawn, is it shown in the photos?


The post and 2x4 I've marked in the picture below were added after the fact and cannot be considered structural. The top piece is an old 2x4 on its side; often this was added as a attempt to mitigate (IMO) floor bounce. While it may help from a "feel" perspective, it is not a effective overall.

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Old 06-17-2019, 07:12 AM   #9
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That's the beam I refer to. Would that beam not being supported on end cause time to com be loose asking the length of the beam and to the immediate sides? The client is saying that mopping loosened it due to not being sealed. Non of the mortar is degraded. We used an air chisel to remove. It was too hard to used a hammer and chisel. He's a Google expert. I'm looking for the primary reason so it can be addressed. I believe it's from flex and want it to be structurally sound. He thinks water and wants it done over with out being supported. He refuses to listen to the effects of deflection.
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Old 06-17-2019, 07:13 AM   #10
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By the way those are lapped joist. They don't straddle the beam. The extent from the beam in both directions.
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Old 06-17-2019, 08:30 AM   #11
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I'd say that's not a beam; its a scabbed in 2x4 someone recycled from somewhere (you can see where the old lathe was nailed previously).

IMO the post and 2x4 cannot be considered as adequate support for the the floor or contributing in any manner to the defection rating of the floor above.

I've no idea to the defection factor for the remaining structure given the overall poor condition of the wood based on your photo.

Sorry I can't be of more help.

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Old 06-17-2019, 08:50 AM   #12
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That was more than enough help. Sometimes all a person needs is confirmation. By the way it was a stair stringer.
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Old 06-17-2019, 11:12 AM   #13
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Quote:
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By the way it was a stair stringer.
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