# Point load on basement slab



## Beniah Naylor (Mar 29, 2021)

This is something we deal with fairly regularly.

Existing house, basement remodel, the owner wants to remove a bearing wall and replace it with an LVL beam. He gets the beam properly sized, and then he wants to hold one side of the LVL up with a column made of 2 2x4s, or some other effective means. His new column will now be bearing on the regular 4" basement slab, with no footing, that was not originally intended to carry whatever load is on the LVL as a point load.

Clearly, there is a certain amount of weight that the 4" slab can handle, but we don't know if it is really 4" thick, if it is reinforced, or what surface it was poured on.

So, I want to know how other jurisdictions handle this situation? How do you determine if they really need to cut the floor and add a footing, or if they can get away with a small point load on a regular slab? 

Best case scenario, I would like to figure out a rule of thumb, like if the point load is only 1,000 lbs. we don't worry about it punching through the slab, more than 1,000 lbs. and they need to put in a footing. Of course, in the real world, it probably isn't that easy...


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## Joe.B (Mar 29, 2021)

Get an engineer. If they sign off on it then it's fine, if not they will design a solution for you.


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## classicT (Mar 29, 2021)

If IRC, 6" think footing minimum. As for sizing footing, take the total reaction, divide by 1500 (or known soil load), then take the square root, then multiple by 12. Value calculated is the minimum width of footing.


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## steveray (Mar 29, 2021)

Like cT said....does not meet IRC footing min....engineer or proper footing


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## ORinspector (Mar 29, 2021)

While not the same situation you might be able to section AH105 section from the 2018 IRC appendix H for some guidance which allows up to a 750 lb load on a 3.5 in slab.


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## Mark K (Mar 29, 2021)

If a proscriptive provision does not provide the answer the applicant needs to provide information to justify their proposal.  An engineer will be needed to provide that justification

Suggest that the quickest and simplest solution is to locate a spread footing under the new column.


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## Beniah Naylor (Mar 29, 2021)

These are good answers.

Follow-up question - When do you start requiring an engineer review or a spread footing? Say you had a 3' doorway in the basement in a load bearing wall, and you properly sized a longer header and extended the doorway to be 5' long, with one side bearing on a two 2x4s creating a point load on the slab. Now, you only extended the header two feet, maybe picked up one or two more floor joists, but maybe not a ton of weight added. So, would you require a footing for that? What if you only extended the header by one foot, instead of two?

Clearly, if you had a big span and a lot of weight, you would certainly need PE review or footings added.

So where do you draw the line on an existing house in your jurisdiction? If they only add a little weight to a point load in an existing house would you let it slide, or do you have a no-tolerance approach? If you would allow it, how much weight would you be comfortable with? 

I guess I'm really just trying to figure out how much weight you guys would be comfortable with someone putting on a 4x4 area of a 3.5" slab. I mean... I think everyone here would agree that it would hold 100 lbs pretty well... maybe the 750 lbs from Appendix H... might even hold 1,000 if it doesn't have to deal with wind or snow loads... etc...

I'm just trying to get a feel for where I should start getting nervous about the point load on a 3.5" slab. I haven't seen enough failures in similar circumstances to gauge this effectively.


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## steveray (Mar 29, 2021)

If it is a bearing wall it already has a strip footing under it....Assumedly....


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## Joe.B (Mar 29, 2021)

If it's not clearly prescriptive from the building code then it's an engineered design.


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## steveray (Mar 29, 2021)

If you can confirm it is a 4" slab then maybe you could say the force transfer becomes 12" at the bottom of the slab so you have a 1sqft footing as far as bearing (X soil bearing capacity)....But you would be neglecting any punch through and anything else that makes it engineering...


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## redeyedfly (Mar 29, 2021)

steveray said:


> If you can confirm it is a 4" slab then maybe you could say the force transfer becomes 12" at the bottom of the slab so you have a 1sqft footing as far as bearing (X soil bearing capacity)....But you would be neglecting any punch through and anything else that makes it engineering...


The 12" is the punch shear dim.  Assume a 45 deg shear plane through the slab (footing) from the edge of the column.  So a 4" square column would have a 12" square effective bearing area.  That assumes no reinforcment.  It gets much more engineery once you start adding reinforcement and your footing becomes a bending plate with spring supports.  

I would be ok with a 1500# point load on a 4" slab by inspection.


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## TheCommish (Mar 29, 2021)

Core a small hole to see what the slab actual is.  Look at table 403.1(1) 

or cut out the slab and pour a 24x24 pad, 12 inch thick install 3 laly column the grout in the floor


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## jar546 (Mar 29, 2021)

I am in the prescriptive camp.  A 4" thick slab (probably 3-1/2") does not meet the requirements as a footer, therefore if you want to use it, you need an engineer to sign off on it.  By today's standards, you won't have any problem getting a PE so sign and stamp there name for a price.  I would think it would be prudent to just meet the code prescriptively and be done with it.  The only thing a 4" slab should support would be partition walls.


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## Mark K (Mar 30, 2021)

Applying the prescriptive provisions how did the owner size the LVL without consulting an engineer?  For essentially the same price an engineer could size the LVL and address the foundation issue.


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## steveray (Mar 30, 2021)

Mark K said:


> Applying the prescriptive provisions how did the owner size the LVL without consulting an engineer?  For essentially the same price an engineer could size the LVL and address the foundation issue.


Manufacturers installation instructions....


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## rktect 1 (Mar 30, 2021)

Mark K said:


> Applying the prescriptive provisions how did the owner size the LVL without consulting an engineer?  For essentially the same price an engineer could size the LVL and address the foundation issue.


Do you have a copy of Weyerhauser I-Joist?






						Document Library
					






					www.weyerhaeuser.com


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## tmurray (Mar 30, 2021)

Here, we have had the floor opened up in every single project at this scope to install code compliant column pads.

You would be amazed how many times I've found no strip footing under a load bearing wall when inspecting these projects. Don't assume anything.


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## my250r11 (Mar 30, 2021)

We would require a footing or an engineer.


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## Mark K (Mar 30, 2021)

Whether the solution is an I-joist or an LVL the manufacturers report is not a proscriptive provision recognized by the code.


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## steveray (Mar 31, 2021)

So they are produced to a standard:
R502.1.2 Prefabricated wood I-joists. Structural capacities
and design provisions for prefabricated wood I-joists
shall be established and monitored in accordance with
ASTM D 5055.
R502.1.3 Structural glued laminated timbers. Glued
laminated timbers shall be manufactured and identified as
required in ANSI/AITC A190.1 and ASTM D 3737.
R502.1.4 Structural log members. Structural log members
shall comply with the provisions of ICC-400.
R502.1.5 Structural composite lumber. Structural
capacities for structural composite lumber shall be established
and monitored in accordance with ASTM D 5456.
R502.1.6 Cross-laminated timber. Cross-laminated timber
shall be manufactured and identified as required by
ANSI/APA PRG 320.

That standard is then used to produce manufacturers installation instructions (span charts)..

What's the problem?...Do you require engineering when someone uses joist hangers or do you use the manufacturers installation instructions?

R502.6 Bearing. The ends of each joist, beam or girder shall
have not less than 11/2 inches (38 mm) of bearing on wood or
metal and not less than 3 inches (76 mm) on masonry or concrete
except where supported on a 1-inch by 4-inch (25 mm
by 102 mm) ribbon strip and nailed to the adjacent stud or by
the use of approved joist hangers.

As hangers are not really prescriptive....It is whatever we will "approve"........


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## jar546 (Mar 31, 2021)

Mark K said:


> Applying the prescriptive provisions how did the owner size the LVL without consulting an engineer?  For essentially the same price an engineer could size the LVL and address the foundation issue.


We accept cut sheets from the manufacturer showing exactly how the lvl will be used.  Most of the manufacturers have PE on staff to provide these so we don't need to go to an outside engineer.


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## rktect 1 (Mar 31, 2021)

steveray said:


> So they are produced to a standard:
> R502.1.2 Prefabricated wood I-joists. Structural capacities
> and design provisions for prefabricated wood I-joists
> shall be established and monitored in accordance with
> ...


Boom,.....done and done.


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## Beniah Naylor (Mar 31, 2021)

Mark K said:


> Whether the solution is an I-joist or an LVL the manufacturers report is not a proscriptive provision recognized by the code.


Not code, but it is an alternative material and method that we accept in our jurisdiction that we deem to be satisfactory and complies with the intent of the provisions of the code.

The whole issue here is that we have a fairly small municipality and we try not to be too rigid if we can tell something will probably work. If we had a larger jurisdiction, there is no way I would take the extra time to study out something like point load on a slab when I could just tell them to put in a footing or get an engineer.

I certainly don't want anything structural to fail, but if it had turned out to be a simple calculation that I was comfortable with I would have been willing to work with people, if I could verify that the structure would be safe. But, the simple answer to make them put in a footing definitely is easier for me...

I appreciate these answers, they were really helpful.


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## jar546 (Mar 31, 2021)

Beniah Naylor said:


> Not code, but it is an alternative material and method that we accept in our jurisdiction that we deem to be satisfactory and complies with the intent of the provisions of the code.
> 
> The whole issue here is that we have a fairly small municipality and we try not to be too rigid if we can tell something will probably work. If we had a larger jurisdiction, there is no way I would take the extra time to study out something like point load on a slab when I could just tell them to put in a footing or get an engineer.
> 
> ...


How do you verify the LVL is properly sized?
Do you require a layout from the manufacturer for I-Joist systems?


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## Mark K (Mar 31, 2021)

The standards for LVL and I-joists provide the user with the allowable values to be used in the calculations.  The manufactures span charts while useful are not code.  Implicit in span charts are certain assumptions.  In the code are span charts for sawn lumber but not for engineered lumber.

It would be informative if you can show us a standard included in the IBC or IRC to determine the capacity of joist hangers.

Is the code what was legally adopted or is it "...whatever we will "approve"...."  Then why do you need a building code?


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## Mark K (Mar 31, 2021)

At what point does the building department transition from checking for code compliance and in effect becomes the de facto engineer of the project?  When this line is crossed most legal theories would recognize that the building department legal immunity no longer exists


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## jar546 (Mar 31, 2021)

Mark K said:


> At what point does the building department transition from checking for code compliance and in effect becomes the de facto engineer of the project?  When this line is crossed most legal theories would recognize that the building department legal immunity no longer exists


I don't believe there is a fine line, I believe it is our duty to work within the scope of the code.  All span tables are the result of engineering.  If every single job had to be engineered, although to you, it may be utopia, to the rest of the world it is not practical.  We are not specifying the job, we are ensuring that what was submitted meets the intent of the code, which may include using data from manufacturers such as Simpson Strong-Tie provides in their manuals.  You, as an architect may provide a drawing with specs but if we find out that you spec'd out the wrong metal ties for the lateral load then we will will question you on it.  We are not telling you what to use, just telling you that what you spec'd out is inadequate.  

Again, LVL manufacturers will provide cut sheets showing the exact use and loading of each LVL.  I don't need their span tables but I will accept them as an alternative method and material when there is sufficient evidence from the manufacturer that it is being used within the design and meets or exceeds the loading.


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## Mark K (Mar 31, 2021)

jar546 said:


> We accept cut sheets from the manufacturer showing exactly how the lvl will be used.  Most of the manufacturers have PE on staff to provide these so we don't need to go to an outside engineer.


Does the manufacture have an engineer stamp and sign the recommendations?  What does your state licensing law say.  The need to have a professional engineer involved is determined by the states licensing laws and not by he building code or the policy of the building department.


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## redeyedfly (Mar 31, 2021)

Mark K said:


> Does the manufacture have an engineer stamp and sign the recommendations?  What does your state licensing law say.  The need to have a professional engineer involved is determined by the states licensing laws and not by he building code or the policy of the building department.


They do extensive testing and provide ESR reports, all done by engineers.  Lumber yards will also size and stamp engineered lumber for projects.  Are you suggesting Weyerhauser just guesses at their technical specifications?  Is there something more complicated about sizing simple span beams from Weyerhausers tables than from the IRC tables for dimensional lumber?

When is the last time you even heard of a structural failure in IRC construction?  Light frame structures are exceedingly redundant structurally.   

You seem to be making a problem where there isn't one.


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## Mark K (Mar 31, 2021)

I am just pointing out that if your state licensing laws require a professional engineer sign and seal documents then either the manufacturers, or lumber yards, engineer must stamp and sign the document or the Owner must hire an engineer to to provide the engineering oversight.  The building code or the building official cannot change the licensing law.

From a legal perspective until the building code provides span tables for engineered lumber there are no span tables that can be quoted to establish compliance.  This is not a question of the validity of the manufacturers calculations but rather a reflection of the legal reality.

While light frame construction is fairly forgiving, individuals who do not know what they are doing can create situations where there is non compliance.  My experience is that licensed engineers are less likely to cause these problems related to their scope of services.

There is a need to have a discussion of he difference between the plan checker and inspectors checking for code compliance and acting as the designer of the project.  This is of concern because of liability exposure but also because a building department employee who lacks an engineering education may not identify a problem.


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## redeyedfly (Mar 31, 2021)

Mark K said:


> I am just pointing out that if your state licensing laws require a professional engineer sign and seal documents then either the manufacturers, or lumber yards, engineer must stamp and sign the document or the Owner must hire an engineer to to provide the engineering oversight.  The building code or the building official cannot change the licensing law.
> 
> From a legal perspective until the building code provides span tables for engineered lumber there are no span tables that can be quoted to establish compliance.  This is not a question of the validity of the manufacturers calculations but rather a reflection of the legal reality.
> 
> ...


I think the relevant code sections are provided above to establish that engineered lumber is in compliance if it follows the manufacturers published technical requirements.  I AM a structural engineer and I don't think you need an engineer to design typical IRC.  I was sizing Microllams long before I ever set foot in an engineering classroom.  

Fun fact, the SEOR typically doesn't design I-joists for IBC projects.  They delegate it to the I-joist supplier.  They are a deferred submittal and come with a PE stamp from the supplier.  They'll provide the same service for IRC.


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## Mark K (Apr 1, 2021)

redeyedfly​
You have obviously practiced structural engineering in another state than I have.  In California the SEOR does design/select the I-Joists and there is no need for the I-joist supplier to provide an engineers stamp since the SEOR's stamp is all that is needed.  By the way in California Civil Engineers can be the EOR for most projects.

The fact that the supplier has an engineer stamp and sign the design supports my contention that there is no prescriptive provisions, such as span tables, for engineered lumber and that an engineers involvement is needed.

Whether you you need an engineer to design a typical IRC project really is two questions.  They are, can a non licensed individual perform the tasks and whether it is legal under the licensing laws.  The answer to the first is largely subjective.  While there are some non-licensed individuals can produce a "satisfactory" design in some situations, those without the  technical training often do not have an appreciation of their limitations.  I have seen too many individuals who believe they know more than they really do.  The real question is how much  risk/uncertainty are you willing to accept.

Compliance with the licensing laws is a separate issue that is defined by the state licensing laws and not by the building code or the preferences of the building official.  Unless there is a clear exemption in state law an engineers involvement is needed.

From a building code perspective the manufacturers published technical requirements are not relevant.  What is relevant are the standards adopted by the code and the properties of the manufacturers I-joist derived from a testing program defined by the code standards.  Yes the engineer should be aware of the manufacturers recommendations but that is not a code compliance issue.


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## redeyedfly (Apr 1, 2021)

Mark K said:


> redeyedfly​
> You have obviously practiced structural engineering in another state than I have.  In California the SEOR does design/select the I-Joists and there is no need for the I-joist supplier to provide an engineers stamp since the SEOR's stamp is all that is needed.  By the way in California Civil Engineers can be the EOR for most projects.


Nearly all structural engineers are civil engineers, a few are architectural engineers.  In California you need to be an SE to sign as an SEOR, not a PE.
You might want to look a little closer at who is actually signing the I-joist designs.  The SEOR will size the I-joists for coordination with arch but they leave the final detailed design to the supplier.  If the SEOR is laying out the location of every I-joist to accommodate all superimposed loads and other coordination for MEP they are wasting their fee.    

I'm not going to show you again where the code allows engineered lumber prescriptively, others have done that.  You go ahead and die on this pointless hill.


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## Mark K (Apr 1, 2021)

In California a Civil Engineer can sign for any structural work with the exception of hospitals and public schools.  All Structural Engineers are registered Civil Engineers.  Thus in  these cases the engineer taking responsibility for the design of the structural work can be a Civil Engineer without the structural authority.  In reality the vast majority of engineers signing for structural work are Structural Engineers even if not required by licensing law.  In these cases it is their authority as a Civil Engineer that allows them to act as the engineer or record for the structural work.

Not all jurisdictions would accept I-joists as a deferred submittal.

California does not recognize architectural engineers as being a separate license.  I am a CE and a SE and my undergraduate degree was in architectural engineering.  While California recognizes that a CE is a PE there is no generic PE license, instead engineers are licensed by discipline.

It needs to be appreciated that licensing laws vary in different states.  In addition local practice can vary.


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## ADAguy (Apr 5, 2021)

Joist hangers (manufactured) are subject to testing and acceptance


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## Mark K (Apr 5, 2021)

Who can identify the standard referenced in the CBC or one of the reference standards referenced by the CBC that defines the required testing for joist hangers?


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## classicT (Apr 5, 2021)

Not into CA, but per the _IRC_, this is what I will hang my hat on.

*R502.6 Bearing*​The ends of each joist, beam or girder shall have not less than 11/2 inches (38 mm) of bearing on wood or metal, have not less than 3 inches of bearing (76 mm) on masonry or concrete or be supported by _approved _joist hangers. Alternatively, the ends of joists shall be supported on a 1-inch by 4-inch (25 mm by 102 mm) ribbon strip and shall be nailed to the adjacent stud. The bearing on masonry or concrete shall be direct, or a sill plate of 2-inch-minimum (51 mm) nominal thickness shall be provided under the joist, beam or girder. The sill plate shall provide a minimum nominal bearing area of 48 square inches (30 865 mm2).​
Note that the word "approved" is italicized, meaning that it is a defined term. Per Ch. 2, definition as follows.

*[RB] *APPROVED. Acceptable to the building official.​
So not to be blunt, but I think it is due.... "It is approved because I say it is", is an  acceptable answer. Simpson/MiTEK/etc. all have sufficient documentation and testing to support the design and use of their products. If used per the manufacturers specifications, it is well within my authority as a building official to accept the use of these products.


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## Mark K (Apr 5, 2021)

We need objective criteria that has been properly adopted.  Then the acceptance by the building official would be based on whether the products complied with the standard.

We are a country of laws not an authoritarian state where individuals act as the sovereign.

Many states would consider delegating the decision to a non governmental entity such as Simpson to be illegal.

The words "acceptable to the building official" are an illegal power grab by building officials.

How would you feel if the police gave you a ticket with no other justification that the police officer wished to?  According to the proposed interpretation a criminal has more rights than the individual who applies for a building permit.


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## jar546 (Apr 5, 2021)

classicT said:


> Not into CA, but per the _IRC_, this is what I will hang my hat on.
> 
> *R502.6 Bearing*​The ends of each joist, beam or girder shall have not less than 11/2 inches (38 mm) of bearing on wood or metal, have not less than 3 inches of bearing (76 mm) on masonry or concrete or be supported by _approved _joist hangers. Alternatively, the ends of joists shall be supported on a 1-inch by 4-inch (25 mm by 102 mm) ribbon strip and shall be nailed to the adjacent stud. The bearing on masonry or concrete shall be direct, or a sill plate of 2-inch-minimum (51 mm) nominal thickness shall be provided under the joist, beam or girder. The sill plate shall provide a minimum nominal bearing area of 48 square inches (30 865 mm2).​
> Note that the word "approved" is italicized, meaning that it is a defined term. Per Ch. 2, definition as follows.
> ...


I'm with this guy.


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## jar546 (Apr 5, 2021)

Mark K said:


> We need objective criteria that has been properly adopted.  Then the acceptance by the building official would be based on whether the products complied with the standard.
> 
> We are a country of laws not an authoritarian state where individuals act as the sovereign.
> 
> ...



Which is why I use the search function of the Florida Building Code Commission to find products like this:


			https://floridabuilding.org/upload/PR_Instl_Docs/FL11496_R5_II_er_0130.pdf


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## jar546 (Apr 5, 2021)

Search here:


			https://floridabuilding.org/pr/pr_app_srch.aspx


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## Mark K (Apr 5, 2021)

My sense is that Florida is unique in the way they deal with approval of products.  I would assume such approvals are only bestowed after they have gone through a process similar to the adoption of regulations.


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## Paul Sweet (Apr 7, 2021)

Allowable loads for engineered lumber, joist hangers, etc. are based on load tests as well as calculations and include a very conservative factor of safety.  Professional Engineers are involved in generating the numbers in the tables.  The manufacturers want to produce a safe product.  If they didn't, people would find out and stop using them, and there would be plenty of attorneys anxious to start a class action lawsuit for everything the manufacturer is worth.


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## Mark K (Apr 7, 2021)

There are several questions.  Is the methodology used by the manufacturer appropriate?  Do you trust the manufacturer?  What do you feel is appropriate?  What can be legally compelled?

Building departments are concerned with the question of what can be compelled.  The other questions are the providence of the code writers, the applicant, and the design professional on the project.


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## redeyedfly (Apr 7, 2021)

Mark K said:


> There are several questions.  Is the methodology used by the manufacturer appropriate?  Do you trust the manufacturer?  What do you feel is appropriate?  What can be legally compelled?
> 
> Building departments are concerned with the question of what can be compelled.  The other questions are the providence of the code writers, the applicant, and the design professional on the project.


You've heard of ESRs?  Nothing is specified on a commercial project without an ESR.  That covers everything you're asking about.  

https://icc-es.org/evaluation-report-program/


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## Mark K (Apr 7, 2021)

The ESR has no legal standing.

I have identified an ESR based on test procedure that was inconsistent with the code.  The manufacture was not happy with me but I understand the ESR was changed. The point is that you cannot blindly trust them.  That is one case where I had reason not to trust the manufacturer.


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## redeyedfly (Apr 7, 2021)

You found one ESR out of thousands with an error?  

Better throw out that baby when the bath is done!

The entire point of ESRs is to provide all the information to establish that a product complies with the code for a particular use.  I think you just like to pick things apart that aren't broken.  There are plenty of ambiguities and inconsistencies in the code, justification of joist hangers isn't one of them.


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## Mark K (Apr 7, 2021)

There have been others.


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## ADAguy (Apr 9, 2021)

A " skeptic" remains among us? Much of what Mark has stated in the past remains true, however in many states picking and choosing your issues remains allowed.


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## Darren Emery (Apr 17, 2021)

redeyedfly said:


> The 12" is the punch shear dim.  Assume a 45 deg shear plane through the slab (footing) from the edge of the column.  So a 4" square column would have a 12" square effective bearing area.  That assumes no reinforcment.  It gets much more engineery once you start adding reinforcement and your footing becomes a bending plate with spring supports.
> 
> I would be ok with a 1500# point load on a 4" slab by inspection.


I just want to weigh in with a thumbs up for use of the term "engineery".  gonna have to borrow that one


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