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Unread 07-09-2003, 09:18 PM   #1
bctile601
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failed the deflect-o-lator

builder has large kitchen, 2 x 12's 15' span, passes the ' bounce ' test, however natural stone is being used and the deflect-o-lator says they're short by L / 200
what can be done to remedy this situatuion ??
o, finished sub is exposure 1 plywood glued and screwed ( with gaps ) 1/2" over 3/4" advantech
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Unread 07-09-2003, 10:01 PM   #2
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What's the joist spacing, Brian?

What's under the floor structure? This over crawl space, basement, second floor? What you got?
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Unread 07-10-2003, 11:26 AM   #3
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sorry,

joist spacing is 16" o.c. , is over a basement, i'm guessing here maybe 10-11 ft high from basement concrete to bottom of said joists. steel i beam in center supported by posts / and foundation walls. the 15 ft span i measured from the i beam to the parallel outside foundation wall
again the builder decks the entire place with 3/4" advantech, then glues / screws 1/2" plywood in areas to be tiled
never had a problem in the past with this TCA acceptable system
( f-150 02 )
however, this is the first time i have evere installed any natural stone for this builder. seems the people always select a 12 x 12 ceramic / porcelain floor tile
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Unread 07-10-2003, 01:42 PM   #4
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The simplest solution would be to add a support wall under the joists to bring you into L/720 spec. Is that something your builder would be willing to do?

He could just add maybe a closet area, just a couple feet deep, in that basement (are his basements finished?) along the wall, which would shorten the span of the joists in the affected area.

Or just some posts and a beam if the basement is to remain unfinished.

The only other way I see is to add more joists, which might be easy enough depending upon the stage of construction and how the joists are seated on the ends. You couldn't screw the floor down to them, but if you put construction adhesive on the tops prior to installation, I think you could remain squeak-free.

Actually, you're close enough that Bob could probably tell you what smaller joist could be scabbed to the bottom of those joists to bring the floor into spec. That might be the easiest method of all.
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Unread 07-10-2003, 02:10 PM   #5
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It'll take a 2x10 sistered on each joist to bring this floor up to L/720. Or, like CX suggested, shortening the span by 2 feet by building a closet against the wall.
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Unread 07-10-2003, 02:26 PM   #6
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You could use Laticrete products and find out if they will still warranty stone @ L/480. I think they still do!
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Unread 07-10-2003, 02:57 PM   #7
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Be nice to have two layers of 3/4" instead of the 3/4 and 1/2. If the stone installation happens again that would be my suggestion. Your not bonding directly to the plywood are you?
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Unread 07-10-2003, 03:12 PM   #8
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yes dave, direct-bond to the 1/2". using a medium-bed mortar with additive
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Unread 07-10-2003, 04:17 PM   #9
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I don't like it, but thats me. The Marble Institue of America would vote no too. Tile on wood is one thing, stone is quite another. That is my 2 cents and experience. Yeah, I've done it, and it has bit me a few times too. The only thing going for this is Advantech, which has twice the performance properties of most OSB panels. I applaud that effort. I'm with K_tile, see if you can find a manufacturer to back you up on this. The span isn't L/720 but I am not sure with the Advantech/Ply combo of the bay area. I would have to see if there has been any testing done on that. I know the Advantech panel has had numerous tests with additional underlayments. I also know they caution it is a SUB-FLOOR panel, not to be bonded to, should anyone be thinking about it.
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Unread 07-10-2003, 04:38 PM   #10
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dave, did you read right ? i'm bonding to exp. 1 1/2" plywood that has been glued and screwed ( with gaps ) to the advantech. or, am i reading you wrong ? i'm definetly not bonding to the advantech.

i asked my local distributor ( a TEC outfit ), actually the owner of the company, and he recommended using the medium bed mortar with xtra-flex additive. however, the deflection was not part of the conversation.
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Unread 07-10-2003, 06:33 PM   #11
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Sort of off topic, but... Does anyone know a source for figuring the deflection with TJI joists?
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Unread 07-10-2003, 07:38 PM   #12
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Howdy, Leon.

When Bob (bbcamp) engineered the deflectolator, I think he tried to find sources for engineered-wood structural material and came up short.

It's always been my experience that only the manufacturer of your TJI is gonna have performance specs for it. It's also been my experience that they are quite happy to provide them, and any other information you might want on their products.

Bob will correct me if I misspoke.
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Unread 07-10-2003, 08:36 PM   #13
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In writing...

1/480 of the span for spans up to 14 ft. (4.3 m), and no greater than 7/32 in. (6 mm) for spans over 14 ft. (4.3 m), where a stone finish is adhered to an underlayment and a structural sub-floor.

www.laticrete.com
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Unread 07-11-2003, 06:04 AM   #14
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CX spoke soothely. I couldn't 'ave spoke more soothelier.
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Unread 07-11-2003, 06:36 AM   #15
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Brian,
What I was saying is I have installed stone over 3/4 and 1/2 and it came back on me. I do not know the deflection rating for the sheathing assembly, that would be my concern, not the joist. Depending on the stone, few will take the L/480 on the joist whether the setting material will or not. The comment on Advantech was to reinterate it is a subfloor panel. Bob Potter at Huber, the manufacturer, says he occasionally gets complaints on bond failure. Was never meant to be bonded to. The only other comment I have on the system is unless the used a superior (urethane) adhesive to glue the panel to the joist the panel may rack if it gets wet on one side, but it is rare.
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