# I don't care if you put plywood between your built up beam.......



## jar546

It is not going to effect the fact that prescriptively it does not meet the IRC.

If I use BeamChek it will still not give me that option.  Adding plywood does not do anything prescriptively and from conversations with engineers, unless they plywood is without joints, it adds virtually nothing.

I am getting a lot of failed beams lately during plan review and we are still getting arguments that it is stronger because they will sandwich plywood in between.

Anyone else on board with this one?


----------



## GHRoberts

Since plywood is a structural material, one can include it in engineering computations. I believe if one looks at the APA website, one can determine the effect of joints on a built up beam.

But you are not an engineer, so your engineering opinion is worth just about nothing.

"beamcheck" is not an engineer either. Its opinion is worth just about nothing.


----------



## Fortner

http://www.finehomebuilding.com/how-to/qa/using-plywood-to-build-up-beams.aspx


----------



## jar546

GHRoberts said:
			
		

> Since plywood is a structural material, one can include it in engineering computations. I believe if one looks at the APA website, one can determine the effect of joints on a built up beam.But you are not an engineer, so your engineering opinion is worth just about nothing.
> 
> "beamcheck" is not an engineer either. Its opinion is worth just about nothing.


Exactly George,  since the plywood is not being specified by a structural engineer with calculations, it is useless.  Either meet the code prescriptively or provide engineering.


----------



## docgj

JAR,

Welcome to my world. I have to watch the beam sizing on every residential project. Seems to be the area that all contractors were light on before the codes. It amazes me that the precode buildings are still standing. Anyway I just tell them the beam needs to be X in size for the span they are showing on the plans or they can set more posts or go to LVL's.

Good Luck

docgj


----------



## Mule

Haven't had that problem here. Everybody has gone to glulam or lvl's


----------



## north star

*$ $ $*

Table R602.3(1) DOES allow for the ' site built ' beams  &  headers

[  headers with 1/2" spacers  ].

*$ $ $*


----------



## GHRoberts

jar546 said:
			
		

> Exactly George,  since the plywood is not being specified by a structural engineer with calculations, it is useless.  Either meet the code prescriptively or provide engineering.


Your comment was that plywood adds no strength. I gave you a reference that says that plywood does add strength. I would suggest you get new software. Or at least get your software corrected.

I would make a comment about the APA being accepted as a competent source of engineering designs by AHJs and therefor their opinions and formulas need to be accepted, but I don't know how to say that.


----------



## texasbo

George - I don't think anyone is arguing that plywood adds strength, he said it doesn't get you anything in the code from a prescriptive design standpoint. Could you direct me to prescriptive design information on the APA website showing increased load carrying capability for homemade beams incorporating a creamy plywood filling?

I'd have no problem accepting an APA document outlining such an assembly, provided the beam was built exactly as specified in the document, but I'm not going to allow it without such documentation. Turn in such information with your plans, and we'll take a look at it...

North star: the table references fastening schedules, but I don't see where it allows increased load carrying capability with the plywood.


----------



## mark handler

texasbo said:
			
		

> I'd have no problem accepting an APA document outlining such an assembly, provided the beam was built exactly as specified in the document, but I'm not going to allow it without such documentation. Turn in such information with your plans, and we'll take a look at it...
> 
> .


Technical Topics: Panel Flitch Beam Design Example

Available only as a downloadable pdf file. Updated August 2006.

http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/TT-030.pdf

http://www.apawood.org/level_c.cfm?content=pub_tch_libmain


----------



## texasbo

mark handler said:
			
		

> Technical Topics: Panel Flitch Beam Design ExampleAvailable only as a downloadable pdf file. Updated August 2006.
> 
> http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/TT-030.pdf
> 
> http://www.apawood.org/level_c.cfm?content=pub_tch_libmain


There you go. Turn that in with your beam design for a 12' span with no more than the specified load per foot, and build it exactly per the document, and you're good to go. Note that if joints are in high bending stress areas, max allowable load is to be no more than "without flitch", which is exactly what Jeff had said; it provides virtually no strength increase.


----------



## mtlogcabin

A Flitch Beam has a single steel plate sandwiched between the lumber not multiple 8ft lengths of plywood that would be found on a large garage door opening.

I agree if the plywood is a single length then it would add strength but it is not addressed in the IRC and it would be up to the contractor/designer to provide the source of information he is using to design his header from

GHR

What is the difference between using BeamCheck,  StruCalc, or some other software program or a table from some association to *verify* that what was submitted is adequate? Not being argumentative just trying to understand what your objections to the various software progarms might be.


----------



## mark handler

mtlogcabin said:
			
		

> A Flitch Beam has a single steel plate sandwiched between the lumber


A flitch beam is a compound beam, and does not always contain a steel plate.


----------



## Mark K

You can get some added capacity out of the plywood but you will need to perform some sophisticated calculations, control the orientation of the plywood, and deal with the splices.  If you use plywood to resist bending stresses as opposed to shear stresses the joints could be a real problem on longer members.

I doubt that any software program is set up to deal with a combination of plywood and sawn lumber bending members.

Code wise you can get at certain APA documents, listed as referenced standards in the IBC, when engineering is provided and the IBC is invoked.  The building official is compelled to accept these documents.  Other APA documents legally are only advisory in nature although I would suggest that it would be considered good practice to allow their usage.

Probably the most effective way to solve this problem would be to use an LVL or similar product but this would require engineering unless these products are addressed in the IRC.  The reality is that flitch plates are not very effective just look at the APA sample calculations Mark Handler referenced. Cost of engineering, preparation of details, and added installation labor is very likely exceed the added cost of the more expensive LVL


----------



## rktect 1

jar546 said:
			
		

> It is not going to effect the fact that prescriptively it does not meet the IRC.If I use BeamChek it will still not give me that option.  Adding plywood does not do anything prescriptively and from conversations with engineers, unless they plywood is without joints, it adds virtually nothing.
> 
> I am getting a lot of failed beams lately during plan review and we are still getting arguments that it is stronger because they will sandwich plywood in between.
> 
> Anyone else on board with this one?


Right.  This solution requires a licensed design professional to sign and seal the drawings as well as calcs.  After that, you need to review those and either accept them or show where the licensed DP is in error so that another solution can be provided.  If you were to be looking at this prescriptively, then you can only view it as a double 2x member and iether it meets the code or does not.


----------



## Daddy-0-

We used to sandwich plywood only to fur out the beam to make it flush with a 2x wall. The added strength of the plywood is minimal. Size the beam with the 2x material per charts. This is the safe and best call to make.


----------



## jar546

GHRoberts said:
			
		

> Your comment was that plywood adds no strength. I gave you a reference that says that plywood does add strength. I would suggest you get new software. Or at least get your software corrected.I would make a comment about the APA being accepted as a competent source of engineering designs by AHJs and therefor their opinions and formulas need to be accepted, but I don't know how to say that.


Not what I said but I understand your misinterpretation of my post.  It adds no strength prescriptively but as I stated, I will accept a PE stamp with calculations for our records.


----------



## Pcinspector1

I'm with Daddy-O-, plywood or OSB helps in making beams flush with the studs and plates, never took it to the calc. stage.

pc1


----------



## GHRoberts

mtlogcabin said:
			
		

> GHRWhat is the difference between using BeamCheck,  StruCalc, or some other software program or a table from some association to *verify* that what was submitted is adequate? Not being argumentative just trying to understand what your objections to the various software progarms might be.


You can verify that the design meets code, but there are a large number of cases where the software will reject designs that meet code.

A classic example is a floor sheathed in plywood. The software does calculations without considering the plywood strength and finds the floor not be sufficient. An engineer considers the plywood strength, treats the problem as a diaphragm and finds the floor is sufficient.

In this thread we don't know what type of roof is in place. I could imagine a hip roof design placing no load on the header. And if i was paid to do a design, I could do away with the header completely. Just have to change the load paths.

I am all in favor of giving non-professionals software and letting them design code compliant solutions. The problem is that non-professionals are using software intended for designing code compliant solutions to reject code complaint solutions.


----------



## TJacobs

The problem is the yahoos in the field with machine guns for hammers won't follow the "engineered" design much less the prescriptive.  They wouldn't know a load path from a dirt path.  They are not going to pay you for a design in this area of the country.  They "...did it this way for 30 years".  They are going to badger us with napkin sketches with tomato sauce on them.  "Just tell me what you want me to do..."

I'm with Daddy-O.


----------



## Uncle Bob

I too agree with Daddy-O;

"We used to sandwich plywood only to fur out the beam to make it flush with a 2x wall."

I have never seen plan that called for a plywood sandwich to be added; for the purpose of carrying a load.

Just say; No. (politely)   

Uncle Bob


----------



## mtlogcabin

GHRoberts

Thanks for your response and I see your point. (We have the deflections on the floors set higher than the code minimums (480) So I guess I am guilty of what you have experienced. The 2 jurisdictions that I have worked for never would reject a set of plans. We would ask questions or ask for clarification as your example pointed out but as a policy we work together with the DP's to keep a project moving and get it to the permitting stage.


----------



## north star

*#  # #*

TJacobs said:





> The problem is the yahoos in the field with machine guns for hammers won't followthe "engineered" design much less the prescriptive.           They wouldn't know a load path
> 
> from a dirt path.       They are not going to pay you for a design in this area of the country.
> 
> They "...did it this way for 30 years".             They are going to badger us with napkin sketches
> 
> with tomato sauce on them.   "Just tell me what you want me to do..."


That's just plain funny!           Sadly, ...too true also! 

*#  # #*


----------



## Mule

Question here....

If plywood does not add any structural value then how do TGI floor trusses work?


----------



## mark handler

Mule said:
			
		

> Question here....If plywood does not add any structural value then how do TGI floor trusses work?


They do add limited structural value. The question is, can you quantify it without quality controled conditions; ie: field conditions?

And Should the higher values be used without Engineering calculations, No.


----------



## Mac

Short strips of plywood don't add _significant_ structural value.

Floor trusses have been engineered and evaluated.


----------



## mark handler

Flitch Beam Design & Software

http://www.strucalc.com/general-engineering/flitch-beam-design-software/

Accurate Flitch Beam Design Made Easier with Software

Flitch beam design software is a useful tool for architects, engineers, designers, and builders. Flitch beams are a common type of composite construction. Composite construction materials are formed by combining two or more materials in a way that allows them to function as a single component structurally. Flitch beams are created by layering wood beams with steel plates or plywood in order to form a wider, lighter structural beam. Bolts hold the layered components together to form a single unit.

These advantages make flitch beams a desirable and attractive choice in light frame construction projects:

•they can support heavier loads over longer distances

•are thinner than solid wood or steel beams with similar load-bearing qualities

•can be nailed to other components of wood structures during construction

•are much lighter than solid beams.

Using computer software to design a flitch beam can greatly improve the cost effectiveness of a project by allowing for a more exact and efficient design.  Software packages precisely calculate the needed thickness, depth, and length of each beam much easier than any kind of hand calculation.

Utilizing flitch beam design software eliminates the possibility of using beams that are too thick or too closely spaced together.  This can drastically reduce construction costs by allowing each beam to be more fully utilized to its capacity.

One of the more difficult calculations associated with a flitch beam is that of the Deflection the beam will undergo.  Software packages will carefully calculate the deflection of flitch beams.  Properly constructed flitch beams ensure that all of the components deflect by exactly the same value. The relative stiffness value of steel and wood is vastly different.  When used correctly, structural analysis software will accurately determine the proper interaction of multiple materials.

Bolt size and Spacing in the construction of flitch beams is crucial. A separate article will briefly discuss a simple way of determining the bolt spacing for a flitch beam.

Flitch beam design software is a must-have tool for the careful architect, engineer, or designer.


----------



## peach

Flitch beams have been used for a hundred years.. the headers have rarely been the point of failure (of course, they weren't garage doors).  It's standard practice (with the exception of a double stall garage door).


----------



## Lou Marks

Plywood does add strenght, however,one must use structural grade. The amount is negilble and not worth the effort. <5%, depth is the key to increasing spans and loads in most cases. Cheaper to use engineered wood or flitch plates. Mostly the plywood is the to make the beam the same width as the wall.


----------



## jar546

Lou Marks said:
			
		

> Plywood does add strenght, however,one must use structural grade. The amount is negilble and not worth the effort. <5%, depth is the key to increasing spans and loads in most cases. Cheaper to use engineered wood or flitch plates. Mostly the plywood is the to make the beam the same width as the wall.


I agree.  The point of the OP was essentially this:

Do not use a (3) 2x10 with plywood between the lumber when prescriptively a (4) 2x10 is required then tell me that the plywood adds enough strength to make up the difference UNLESS you have an engineer's stamp to go along with it.


----------

