Floor blocking

[Squirl]

I couldn't find this in any of my framing books.

I will be sheathing the floor with Tongue and Groove 3/4 inch Advantech. By my math advantech panels are 47 1/2 inches.  This will leave a 2.5 inch strip of panel at the last edge.  I was planning on making that up with 2.5" cut pieced of a panel.  This would not have the tongue and groove.

Does this need blocking?  I was curious because this strip will be under the sole plate of the wall, and I was wondering if the sole plate was enough to distribute the load and I didn't have to worry about blocking the floor sheathing.

If it does need blocking, what size?

[PEG688]

The floor sheathing needs to cover all the joist tops , but if this area you're talking about is the side where the joist are nailed to the rim joist it's fine to just butt a ripping of sub-flooring to the edge of the tongue of the last sheets , the plate will cover this joint and the joist will provide the support for the ripping piece.   


Besides if Advance tech is sized to account for a expansion space you may not " loose" as much as your thinking in the width of multiple sheets.   

[Don_P]

This is one of those places where we have not done a good thing. The floor sheathing does a great job of locking the floor system together, and then because we have this undersized sheathing it often leads to a really sorry connection between rim and joists along one edge. Often not a big deal. But if you bolt a porch or deck ledger to that sort of poorly connected rim, there is the weak link. It costs a whole extra row of sheathing to do it the "best" way. Cut down the starter row by about 2' to create a strong connection along both sides of the floor. that wastes alot of sheathing if you cannot use the rippings later. I usually find uses, such as subtreads for stairs, gussets, etc.

[MushCreek]

This is really a pet peeve of mine, with many houses designed around sheet goods on 48" centers. On my barn (exactly 28') I did it the 'right' way, wasting nearly a half sheet on each side. As Don pointed out, there are always uses for the cut-offs, and in the grand scheme of things, it's not really that much money. Still gripes me, though.

[PEG688]

 There more than one way to attach a deck rim joist.

If one laps the wall sheathing down onto the rim you've got a gusset.

If you nail the sole plate down to the sheathing and into the top of the rim you have a series of nail in shear attaching the rim to the sole plate.

If you have solid joist you have three nails per joist attaching the rim to the joist ends , maybe the weakest connection as the nails are in end grain and with drawl.


If you follow the new coming code you'll have a lateral load connection made by Simpsom strong tie which is basically two hold down attached to two corresponding joist , one on the deck , one on the buildig , via a threaded rod.

Could Don p's deck fail by ripping the rim joist off the building with deck lateral loads ,,,,,, yes it could happen. BUT IT"S DAMNED rare to have that exact failure. 

I'm sure he can find a few reports of that exact failure, but in thirty years of building  I've never had a deck fail due to the rim being ripped off by the deck.


Home Home Building has some good deck attachment , and rim flashing details in issue # 228 , July 2012.


         

[PEG688]

  What happened ? I fully expected hundreds , if not thousands,  of links to deck failures with the rim joist ripped clean clear off the building !!!  And the resulting death toll from this to be in the 10's of thousands , sort of like a tsunami death toll count!!

All due to some saving a few sheets of 3/4" sub flooring

[Don_P]

It's more, how to redirect.

The floor sheathing does a great job of locking the floor system together, and then because we have this undersized sheathing it often leads to a really sorry connection between rim and joists along one edge. Often not a big deal.

But, here is how the designer was thinking about it;
Sheathed wall, floor, and roof subsystems, can be designed to function within the total building system to resist lateral forces in addition to supporting vertical loads. These subsystems are commonly referred to as shearwalls (vertical elements) and diaphragms (horizontal elements). A critical consideration in the proper functioning of diaphragms and shearwalls is the connections needed to ensure that these elements act as integral units and that those units in turn are interconnected with the building as a whole to ensure the proper functioning of the entire structure.
........
When properly designed and connected together, the assemblage will function as a horizontal beam that spans between the vertical resisting elements.
In general, a horizontal diaphragm can be thought of as being made up of a shear resisting element (the sheathing) and boundry members (chords and struts).
An analogy is often drawn between a horizontal diaphragm and a steel wide flange beam. In a steel beam the flanges resist most of the moment and the web essentially carries the shear. In a horizontal diaphragm the sheathing corresponds to the web and the chords (floor rims) are assumed to be the flanges.
........
That was fast and loose from two standard wood engineering references. What it goes on to explain is the mechanics of how that properly connected diaphragm interacts with the structure. And we are talking about muffing that connection. Sure you can, and you'll certainly get away with it 99% of the time, I have too. But those guys are assuming a weld where we are throwing in a pop rivet. It doesn't take a whole lot to make that weld.

What I wonder is if we frame in a flat block flush to the top of the floor frame. Nail it from rim to block and from the joist on each side to block. Is the chord adequately connected to develop intended strength? I'll write the engineer at APA and get back.

[PEG688]

How about some CS 16 strap wrapped under the plates , embedded into the foundation , buried 1/2 way to China , then stretched over the roof and back down the other side repeating the under the plates , embedded , and buried 1/2 way to China 

Or we could hope that gravity continues to work for us.      

[flyingvan]

This is all an evil Advantech plot to sell more decking.  A lesson learned by the hotdog/bun package count inequity.  Can't you just roll your joists a little closer than 16" on center so all the joints end up on a joist, and start from whatever edge the deck's on?  Better still, build your decks on cantilevers that run under the entire house instead of a ledger

[PEG688]

That a nice,  cheap looking little floor system.  Simple to!

   One thing you may want to figure on , or figure out , will be getting plumbing , heating ducts , dryer ducts , wiring , etc down into the crawl or up and out of the crawl and into the wall cavities.  You have some "challenges" ahead of you , IF that's your floor system.


Good luck , (you're going to need it),  PEG 

[flyingvan]

 Err...Not sure about the challenges?  What is it you're seeing?  I guess sweating the copper at the high side was a little tough----I kept losing the flame because working up in the joist bay with 18" clearence used up oxygen fast, but I ran all the electrical and drain side while building

The electrical ran up through my forms before the pour.  I don't have pictures of the other two foundation breaches---a 4" ABS drain to the septic and a 2 1/2" ABS drain at the lowest point in case of some flood under the house---I didn't want a bathtub.  Both were well wrapped and can move freely, and the drain has a screen to keep creepies out.
  The mistake was running 4" drain instead of 3" under the house.  I just thought bigger was better, until I found out my through-roof vents had to equal or exceed the cross section area of the main drain, so there's a 1 1/2", 2" and 3" vent coming through. 
    I'm still curious about why you see issues with running the utilities under this floor? 

[Squirl]

Thank you all for the responses.

I was familiar with the diaphragm issues, but I thought with blocking, the diaphragm was complete.  The example I was thinking of was with the AWC high wind and seismic activity framing guides, showed a fully blocked wall was just a strong as using one sheet.  I did not think the diaphragm would have been that effected by the 2" strip.

I have not built any decks, nor do I plan too.  I like to keep my building design flexible in case someone decides to do something after I am gone.  I am almost positive any leftover sheathing will be wasted.  I have nothing else in my design for 23/32 sheathing.  I have had a 2x2 piece of 3/4 ply for the past 3 years that I have been trying to find a use for.  To get the tongue and groove edge on that many cut pieces would require a lot of waste (3-4 sheets) but there may be something I am missing.  The front (north) side of the house will be the only door.  Since this is the kitchen, composting toilet, and utility room side, it is the least likely side of the house for a deck or expansion.  If there is a weak side, I will make it this one, instead of the other one as I had planned.

Currently the rim joist is attached to each joist by 6-16d nails, 10-16d nails where the rim joist butts up over a joist, and toe nailed to the sill every 12 inches with 16d nails.  It will be completely covered by the wall sheathing which will be fully blocked.  It will be fully toe nailed every 12 inches with the sole plate of the wall above it.  I currently only plan to run the water intake line through the floor joists.  I plan to run all other electrical and plumbing through the 2x10 wall studs.

I did think about the lateral and shear forces a bit in the floor design.  With the low height (8' single story, 6/12 pitch roof 2' crawl space), over sized lumber (2x12 joists, 2x10 studs), low length to width ratio (1.5), it was in the least concerns for design criteria in the AWC high wind framing guidelines.

I'm not very familiar with decks, but as far as rim joist pull with a deck, couldn't this be solved with a better deck foundation?  Such as not supporting the deck by the rim joist?

[Don_P]

The APA Help Desk is a great resource whenever you have a question on plywood or engineered wood products. They almost always respond the next business day. Here was his response;

APA and model building code load span tables and other standard references are all based on minimum 24" panel widths. Using smaller widths requires reductions in load capacity.

Additionally the 2009 and 2012 International Building Code references the ANSI/AF&PA SDPWS-2008: Special Design Provisions For Wind And Seismic, as the standard for horizontal diaphragm and shear wall design. Section 4.2.7.1.1, Item 1. of the standard states, [Diaphragm] "Panels shall not be less than 4' x 8' except at boundaries and changes in framing where minimum panel dimension shall be 24" unless all edges of the undersized panels are supported by and fastened to framing members or blocking." And the 2006 IBC Section 2305.2.4 states "... not less than 4 feet by 8 feet except at boundaries and changes in framing where minimum sheet dimension shall be 24 inches unless all edges of the undersized sheets are supported by and fastened to framing members or blocking."

I hope this information will be of assistance to you.  Please let us know if we can supply you with further information.

Regards,
Merritt Kline
Product Support Specialist
Wood Products Support Help Desk
APA
253-620-7400 (phone)
253-565-7265 (fax)
merritt.kline@apawood.org
www.APAwood.org

[MountainDon]

This (47 1/2" wide T&G sheathing) is why our cabin was designed and built 15.75 feet wide and not a full 16 feet.     




PS, just back from Yosemite. More later, elsewhere. 

[PEG688]

Err...Not sure about the challenges?  What is it you're seeing?  I guess sweating the copper at the high side was a little tough----I kept losing the flame because working up in the joist bay with 18" clearence used up oxygen fast, but I ran all the electrical and drain side while building

The electrical ran up through my forms before the pour.  I don't have pictures of the other two foundation breaches---a 4" ABS drain to the septic and a 2 1/2" ABS drain at the lowest point in case of some flood under the house---I didn't want a bathtub.  Both were well wrapped and can move freely, and the drain has a screen to keep creepies out.
  The mistake was running 4" drain instead of 3" under the house.  I just thought bigger was better, until I found out my through-roof vents had to equal or exceed the cross section area of the main drain, so there's a 1 1/2", 2" and 3" vent coming through. 
    I'm still curious about why you see issues with running the utilities under this floor?

  Boring thru the beams , did you exceed the size hole , and the back wall it appear the beam is on the concrete.  Generally plumbers and heating guys make a mess of beams , or try to.   Maybe you have more room to run pipes , ducts , and what not than the first photo seems to show.

[flyingvan]

Why bore through them?  I just went under them.  The ones in the back there you mention----the 3" drain turns 45 degrees  (I had to box it in a little inside but it will be hidden behind a base cabinet)  The other one, for the kitchen, is past the beam---it's a rim joist there so  the 2" pipe just went straight down.  The only place that WAS a pain was the upstairs toilet drain----that hole had to go through a TJI (just one) it was within the permissible sizes, but just barely

[PEG688]

Currently the rim joist is attached to each joist by 6-16d nails, 10-16d nails where the rim joist butts up over a joist, and toe nailed to the sill every 12 inches with 16d nails.  It will be completely covered by the wall sheathing which will be fully blocked.  It will be fully toe nailed every 12 inches with the sole plate of the wall above it.  I currently only plan to run the water intake line through the floor joists.  I plan to run all other electrical and plumbing through the 2x10 wall studs.

I did think about the lateral and shear forces a bit in the floor design.  With the low height (8' single story, 6/12 pitch roof 2' crawl space), over sized lumber (2x12 joists, 2x10 studs), low length to width ratio (1.5), it was in the least concerns for design criteria in the AWC high wind framing guidelines.

I'm not very familiar with decks, but as far as rim joist pull with a deck, couldn't this be solved with a better deck foundation?  Such as not supporting the deck by the rim joist?

Those toe nails galv-ie's , they need to be if they are going into ACQ treated lumber. Other than that , you'll be fine.

  Inspectors just have to find fault and demand over building at every junction.  You're not building a 3,  4,  5 or more  story  dwelling  or a sky scrapper.

  Mr. Simpson has sold the Govt. a bill of goods that they now demand the sleeple must use in order to comply with Mr. Simpson's money needs.   

If we had to have this type of attachment how in the hell do 200 year old houses still stay together without one sheet of play-wood in them??

End of Mini Rant   No offense intended to building inspector ,  Govt. thugs /  enforcement  workers.

[Squirl]

They are galvanized nails. 

On the blocking itself. 

What size lumber?  How do I lay it?

All the visual framing guides I have only cover fire blocking, which the cavity must fully be blocked.
I read someplace (here I believe) that sheathing blocking can be a 2x4, just enough to insure full penetration depth of the nail.

The floor doesn't concern me as much because it will be the outside edge and will not effect the insulation value.  Although the code simply states that "Unsupported edges shall have tongue-and-groove joints or shall be supported by blocking", it doesn't state "the full height of the joist."

The AWC wind and seismic guide has little direction on blocking.  There are pictures of 2x laid flat, 2x on edge, and 3x on edge.  I could find no reference in it that the blocking had to be the same size as the joist/stud.

[Don_P]

For diaphragm blocking a 2x4  nailed flatways does a good job.

[PEG688]

For diaphragm blocking a 2x4  nailed flatways does a good job.

I've had inspector call blocking that didn't conform to the 3" nominal rule, and I've read a shear wall is considered 17% weaker with less than 3" nominal blocking.

Would this be old 2003 IRC wording?  I can't find  much on line about shear wall blocking and which direction it should be installed , on the flat or on edge. So what you got on those points Don?   

[Don_P]

If we are talking about attempting to block that little strip under the wall, it won't create an attachment to the floor's web. Anything we do to better attach the sheathing, the web, to the rim, the chord, is going to be an improvement.
At a 2' finishing sheet width, a 2x4 block flatways or T&G edges will create a prescriptive diaphragm. What the engineer from APA described above, the prescriptive answer. From there consult the diaphragm tables for allowable shear. They do include 2x and 3x framing, there is an increase for 3x framing. Just looking down the numbers, I think the inspector is about right for framing. For blocking I don't see it in black and white nor do I see it in intent, but you are in a different area. It would be a little stronger.  You've seen these tables showing different panel layouts and blocking methods, I'm reading from the '05 NDS supplements, but I'm pretty sure I've seen this on the awc or apa website. As always read the footnotes.

From the NDS;
"Diaphragms vary considerably in load carrying capacity, depending on whether they are blocked or unblocked. Blocking consists of lightweight nailers, usually 2x4's, framed between the joists or other primary structural supports for the specific purpose of connecting the edges of the panels."( The accompanying diagram shows full depth solid bridging being used as blocking and 2x's also shown with the comment "may also be installed flatwise.") "The reason for blocking in diaphragms is to allow connection of panels at all edges for better shear transfer. Design loads for unblocked diaphragms may be limited by buckling of the unsupported panel edges. Additional nailing will have little effect on the buckling performance of the unblocked diaphragm. For the same nail spacing, design load on a blocked diaphragm can be designed to be as high as twice the design load of its unblocked counterpart."
...............
The blocking holds the panel edge down in plane, the minimum size of the panel connects the rim, the outer chord, to the web, the floor sheathing, where the blocking or a T&G edge does it's job of holding the web flat and in plane.

This is a situation where they are assuming you are making an assembly that is more than the sum of its' parts. A web of plywood well connected to the framing to create a floor "beam". One alternative that springs to mind from recent threads might be a heavy timber sill with mortised in posts and studs capable of resisting horizontal wind loads.

A braced or shear wall is attached to a floor diaphragm and a box type structure is created, very strong.  The boundry must be connected to the field to achieve the perfomance assumed, the narrow strip cannot do that. It doesn't apply to just 4 and 5 story offices, it is how to create strength, from a cardboard box to a skyscraper. Flop an open topped box around, notice the rigidity of that open top, then tape the flaps, the diaphragm, down around the boundry and it'll calm down. Now tape the buckling middle seam down to block it in place. It just locked into a box type structure, there's the intent.