Engineered Designed Foundation for Residential Construction

[jod0001]

Ok, I am a building inspector and I’m am well aware that the IRC lays out the footing width, depth, # size and amount of rebar that is required for footings/turndowns BUT… I recently had a conversation with my supervisor regarding engineered designed footing/turndowns for residential construction. In the past if a contractor has an engineered design for a portion of the residential footings, let say for sake of discussion it’s a simple single story rectangle house and the foundation plan is stamped by the structural engineer and calls for a footing size of 24” wide, 16” in depth, with 3 # 5s continuous and #4 cross bars every 24” a long the entire length of the right side of the house but for the other 3 side the engineer stated use the IRC for required footing design. As I said in the past I would enforce the engineered design where called out on the foundation plan. I was told by my supervisor that unless the engineer designs the entire foundation plan (all details of the foundation/slab are designed by an engineer that go beyond the IRC requirements) the IRC foundation/slab requirements should be enforced and to not enforce the engineer design. I tried to reason with him stating although it may not be apparent at the moment as to why they used an engineer to design that section of the foundation, they did and when the engineer ran the calculations for whatever came up with this footing design/detail, my supervisor didn’t want to hear that. When I left his office I told myself that I would continue to enforce it as I had and if my supervisor was to question why I continued to enforce it I would reach out to the structural engineer for an explanation of the design and then I would ask for it in an email so I could forward it to my supervisor. I hear a lot about immunity but I also hear that if there is an engineered design and I don’t enforce it then if something happens I own it. In my opinion immunity should not be my first line of defense. Am I off my rocker for enforcing this?

I sure would like to hear from some structural engineers and other building inspectors on this topic.

Thanks

 

[jar546]

Thank you for posting and I appreciate your candor. Let me tell you a quick story.

I received a phone call from one of my inspector friends from another county asking me if I could be an expert witness for him as he was being sued by a homeowner. He did the plan review and was doing the inspections for a home designed by an architect. The approved drawings called for 10" thick footings. The contractor used 2x8 forms for 7-1/2" thick footings, which exceeded the prescriptive code requirements. At some point the homeowner and builder got into an argument and the owner decided to hire an engineering firm to dig down along the foundation to prove the footing thickness did not meet the approved plans that he paid for and was expecting. Did they meet the code? yes. Was it per plans? no. A registered design professional signed and sealed the plans showing 10" thick footings, something that the homeowner wanted. The contractor took it upon himself to only put in 7-1/2" footings which was not per plans. The settlement was out of court and cost the contractor and inspector/plans examiner money because neither of them did their job.

For Florida, we use FBC107.4
107.4 Amended construction documents. Work shall be installed in accordance with the approved construction documents, and any changes made during construction that are not in compliance with the approved construction documents shall be resubmitted for approval as an amended set of construction documents.

The contractor should have constructed 10" thick footings or get approval from the RDP for anything less since the drawings were submitted by an RDP. So either 1) build it the way it is drawn and approved or 2) get the RDP to revise the drawings to the way you built it or plan on building it if different than the drawings regardless of whether or not it meets the code.

Let's take angle to look at.

How do you know that the RDP designed it the way they did because of soil issues discovered and they engineered the footing to compensate for that? You don't and it sounds like your supervisor is a little too contractor friendly and not looking at the big picture.

 

[jod0001]

My thought exactly on the soil, luckily in my jurisdiction the contractors will go ahead it get compaction test on the pad and submit the results fairly regularly , they raise the pads up quite a bit but once they open the footings and it rains in them then they may have to be retested if they are soft. I catch a lot of footings that are soft and I will normally give the contractor a chance to remove the soft soil and find hard ground but if they can’t hit hard ground I will ask them to consult an soil engineering firm regarding the soft footing. In some cases along with the soil engineers corrections, the soil engineer will also refer them to a structural engineer too.

What I try to explain to the contractors is doing these extra steps to ensure it’s correct may likely save them a lot of trouble (ie legal defense, hopefully they have good insurance with decent liability limits) down the road and they normally agree, IF they don’t have concrete on site.

But at the end of the day they had an engineer who put his stamp on it and I feel it is necessary to make sure it’s done to his design.

Thank you for your insight on this topic.

 

[Yankee Chronicler]

As a "registered design professional" (I am a licensed architect) as well as a code official, I will say that my view is when a registered design professional elects to follow the prescriptive requirements in the code, then that is that design professional's "engineered" design. He or she has reviewed the relevant parameters and has made a professional judgment that the prescriptive requirements are adequate. The code official has no authority to demand that because the registered design professional used his/her professional expertise, education, training and experience to determine that ONE side of a 4-sided box requires a non-prescriptive design, that the other three sides must also be engineered to a non-prescriptive solution that -- for those three sides -- exceeds what the code requires. Candidly, IMHO your boss is asking to be sued.

However, I would not accept a drawing that only shows one side of the foundation and then has a note for the other three sides that essentially says "to code." According to UpCodes, Alabama's version of the IRC retains the section on information on construction documents:

R106.1.1 Information on Construction Documents.
Construction documents shall be drawn upon suitable material. Electronic media documents are permitted to be submitted where approved by the building official. Construction documents shall be of sufficient clarity to indicate the location, nature and extent of the work proposed and show in detail that it will conform to the provisions of this code and relevant laws, ordinances, rules and regulations, as determined by the building official.

So the foundation drawing(s) need to show "in detail" how all four sides are to be constructed. The builder should not EVER need to open a code book to find out what the other three sides need to be. The engineer's seal applies to the overall design of the foundation, even if three sides are prescriptive and one side is engineered. The details should show the prescriptive information for the three "standard" sides as well as the details for the "engineered" side.

A former State Building Inspector here (now deceased) used to hammer into us pre-COVID when we still had live- in-person training classes, "The code is the least you can accept and the most you can require." Applying that to your example foundation, a licensed professional engineer has determined that the prescriptive requirements of the IRC are sufficient for three sides of the foundation. As the code official, you CANNOT (legally) require anything more for those three sides of the foundation.

 

[Yankee Chronicler]

Thank you for posting and I appreciate your candor. Let me tell you a quick story.

I received a phone call from one of my inspector friends from another county asking me if I could be an expert witness for him as he was being sued by a homeowner. He did the plan review and was doing the inspections for a home designed by an architect. The approved drawings called for 10" thick footings. The contractor used 2x8 forms for 7-1/2" thick footings, which exceeded the prescriptive code requirements. At some point the homeowner and builder got into an argument and the owner decided to hire an engineering firm to dig down along the foundation to prove the footing thickness did not meet the approved plans that he paid for and was expecting. Did they meet the code? yes. Was it per plans? no. A registered design professional signed and sealed the plans showing 10" thick footings, something that the homeowner wanted. The contractor took it upon himself to only put in 7-1/2" footings which was not per plans. The settlement was out of court and cost the contractor and inspector/plans examiner money because neither of them did their job.

For Florida, we use FBC107.4
107.4 Amended construction documents. Work shall be installed in accordance with the approved construction documents, and any changes made during construction that are not in compliance with the approved construction documents shall be resubmitted for approval as an amended set of construction documents.

The contractor should have constructed 10" thick footings or get approval from the RDP for anything less since the drawings were submitted by an RDP. So either 1) build it the way it is drawn and approved or 2) get the RDP to revise the drawings to the way you built it or plan on building it if different than the drawings regardless of whether or not it meets the code.

Let's take angle to look at.

How do you know that the RDP designed it the way they did because of soil issues discovered and they engineered the footing to compensate for that? You don't and it sounds like your supervisor is a little too contractor friendly and not looking at the big picture.

I would agree that in this case the code official screwed the pooch.

Just above I quoted our former State Building Inspector, who often stated in classes that "The code is the least you can accept and the most you can require."

That's true -- as far as it goes. But IMHO that's at the plan review level. Nothing in the code or in law prevents an owner or a designer from exceeding the minimum requirements of the building code. When we approve a set of construction documents, those plans and details become the minimum standard for that building. We should be inspecting to that standard. You used the footing as the example, but how about floor framing? A living room may meet the prescriptive requirements of the code with 2x10 joists, but the owner doesn't want bouncy floors so the designer called for the ground floor to be framed with 2x12s. I approve construction documents calling for the ground floor to be 2x12s. I should not allow 2x10s in the field even if they meet the code, since they don't match what's shown on the approved construction documents.

 

[mtlogcabin]

R301.1.3 Engineered design.
Where a building of otherwise conventional construction contains structural elements exceeding the limits of Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice. The extent of such design need only demonstrate compliance of nonconventional elements with other applicable provisions and shall be compatible with the performance of the conventional framed system. Engineered design in accordance with the International Building Code is permitted for buildings and structures, and parts thereof, included in the scope of this code.

 

[tmurray]

I would say that your inspections would need to be per the approved plans. If they want to reduce the size of the footings to code, have them re-submit plans and have them go through the plan review process again to ensure that no one is overlooking something.

I've had this discussion a lot in the past year or so with foundation contractors. I always preach to have the designer design to the minimum, because we are almost never going to be upset to see a footing that is larger than the plan, but going smaller, omitting reinforcement, etc. is going to throw up some flags and may delay approvals.

 

[mtlogcabin]

because we are almost never going to be upset to see a footing that is larger than the plan,

Foundations are designed to support a specific load and when a designer specify different size foundations within a structure it should be based on the loads they will support. Allowing smaller footings to be increased in size may create a differential settlement within the structure over its live span.

Causes of differential settlements​

• Soil of different lithological characteristics in the horizontal direction (different compressibility and soil compressibility beneath different parts of the foundation structure).
• Drying of soil surface layers.
• The proximity of trees with large roots.
• Piping leaks, sewer drainage etc.
• Excavations near the structure.
• Different dimensions and depth of structure foundation.
• Vibration.

Differential settlements - Causes, methods of prevention and remediation

Settlement of the foundation soil is a vertical displacement of the soil surface caused by the workload of the building. During and after...

www.geotech.hr

 

[bill1952]

designed in accordance with accepted engineering practice

This half belongs in "rural deregulation" thread, but I designed and built a 900 SF detached garage using a rubble trench foundation. 4+ ft deep, drain to daylight, a lot of crushed stone, to nearly grade. 12 x 8 footing, surface bonded block to above grade, and stick framed with ungraded rough sawn on that.

A number of items not clearly within the prescriptive requirements of the NY amended IRC. The rubble trench was designed "accordance with accepted engineering practice", but not by an engineer. Is that possible? I did put rebar in the footing though not required by the IRC where I live. (Feels like one of those things where often building officials require more than the code requires. ) Surface bonding kind of at the periphery if the IRC (though I'm convinced stronger and more waterproof than mortared block). And the ungraded lumber is allowed in NY with a more from the sawmill.
Generally the building is much more stout than a lot of code compliant accessory buildings, and not likely to compromise safety in any way.

 

[mtlogcabin]

but not by an engineer. Is that possible?

Absolutely, there are a number of software programs that will do that for a person.

 

[Yankee Chronicler]

Foundations are designed to support a specific load and when a designer specify different size foundations within a structure it should be based on the loads they will support. Allowing smaller footings to be increased in size may create a differential settlement within the structure over its live span.

OR ... three walls will bear on undisturbed soil of decent bearing capacity, while the fourth wall happens to occur over a finger of poor soil that occurs on one part of the site. So the structural engineer's professional opinion is that the prescriptive footing is appropriate for the three sides on good soil, but that an engineered, reinforced footing is necessary for the fourth wall because it will rest on different soil.

 

[steveray]

OR ... three walls will bear on undisturbed soil of decent bearing capacity, while the fourth wall happens to occur over a finger of poor soil that occurs on one part of the site. So the structural engineer's professional opinion is that the prescriptive footing is appropriate for the three sides on good soil, but that an engineered, reinforced footing is necessary for the fourth wall because it will rest on different soil.

OR...it is built into a bank of crappy soils and has a higher backfill (although that would likely improve the wall as well and maybe a cantilevered footing.) or any number of reasons they beefed up the footing...Impossible to know, inspect to plans...

 

[jod0001]

As a "registered design professional" (I am a licensed architect) as well as a code official, I will say that my view is when a registered design professional elects to follow the prescriptive requirements in the code, then that is that design professional's "engineered" design. He or she has reviewed the relevant parameters and has made a professional judgment that the prescriptive requirements are adequate. The code official has no authority to demand that because the registered design professional used his/her professional expertise, education, training and experience to determine that ONE side of a 4-sided box requires a non-prescriptive design, that the other three sides must also be engineered to a non-prescriptive solution that -- for those three sides -- exceeds what the code requires. Candidly, IMHO your boss is asking to be sued.

However, I would not accept a drawing that only shows one side of the foundation and then has a note for the other three sides that essentially says "to code." According to UpCodes, Alabama's version of the IRC retains the section on information on construction documents:



So the foundation drawing(s) need to show "in detail" how all four sides are to be constructed. The builder should not EVER need to open a code book to find out what the other three sides need to be. The engineer's seal applies to the overall design of the foundation, even if three sides are prescriptive and one side is engineered. The details should show the prescriptive information for the three "standard" sides as well as the details for the "engineered" side.

A former State Building Inspector here (now deceased) used to hammer into us pre-COVID when we still had live- in-person training classes, "The code is the least you can accept and the most you can require." Applying that to your example foundation, a licensed professional engineer has determined that the prescriptive requirements of the IRC are sufficient for three sides of the foundation. As the code official, you CANNOT (legally) require anything more for those three sides of the foundation.

R301.1.3 Engineered design.
Where a building of otherwise conventional construction contains structural elements exceeding the limits of Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice. The extent of such design need only demonstrate compliance of nonconventional elements with other applicable provisions and shall be compatible with the performance of the conventional framed system. Engineered design in accordance with the International Building Code is permitted for buildings and structures, and parts thereof, included in the scope of this code.

I actually showed him this section and he told me that I look at things to black and white, I said code is black and but does allow for exceptions or provide alternative ways for achieving certain things. Thank you for your response.

 

[jod0001]

As a "registered design professional" (I am a licensed architect) as well as a code official, I will say that my view is when a registered design professional elects to follow the prescriptive requirements in the code, then that is that design professional's "engineered" design. He or she has reviewed the relevant parameters and has made a professional judgment that the prescriptive requirements are adequate. The code official has no authority to demand that because the registered design professional used his/her professional expertise, education, training and experience to determine that ONE side of a 4-sided box requires a non-prescriptive design, that the other three sides must also be engineered to a non-prescriptive solution that -- for those three sides -- exceeds what the code requires. Candidly, IMHO your boss is asking to be sued.

However, I would not accept a drawing that only shows one side of the foundation and then has a note for the other three sides that essentially says "to code." According to UpCodes, Alabama's version of the IRC retains the section on information on construction documents:



So the foundation drawing(s) need to show "in detail" how all four sides are to be constructed. The builder should not EVER need to open a code book to find out what the other three sides need to be. The engineer's seal applies to the overall design of the foundation, even if three sides are prescriptive and one side is engineered. The details should show the prescriptive information for the three "standard" sides as well as the details for the "engineered" side.

A former State Building Inspector here (now deceased) used to hammer into us pre-COVID when we still had live- in-person training classes, "The code is the least you can accept and the most you can require." Applying that to your example foundation, a licensed professional engineer has determined that the prescriptive requirements of the IRC are sufficient for three sides of the foundation. As the code official, you CANNOT (legally) require anything more for those three sides of the foundation.

Hey thank you for your response, I know my example was vague on the plan submitted but yes the foundation plan should call out the requirements not just the engineered side, I didn’t put much effort in describing how the plan was submitted(as that was not a concern in my original post) just that one was submitted and one side called for an engineered design and the other section of the foundation plan did not. Also, I have never required any foundation plan that falls under the IRC to go above and beyond the code requirement unless an engineer has submitted a foundation plan with a design that has been signed and stamped. For my example I would only require that one side with the engineered design to be installed as designed. The other 3 sides would would be installed to the IRC code. Thanks again.

 

[Mark K]

This half belongs in "rural deregulation" thread, but I designed and built a 900 SF detached garage using a rubble trench foundation. 4+ ft deep, drain to daylight, a lot of crushed stone, to nearly grade. 12 x 8 footing, surface bonded block to above grade, and stick framed with ungraded rough sawn on that.

A number of items not clearly within the prescriptive requirements of the NY amended IRC. The rubble trench was designed "accordance with accepted engineering practice", but not by an engineer. Is that possible? I did put rebar in the footing though not required by the IRC where I live. (Feels like one of those things where often building officials require more than the code requires. ) Surface bonding kind of at the periphery if the IRC (though I'm convinced stronger and more waterproof than mortared block). And the ungraded lumber is allowed in NY with a more from the sawmill.
Generally the building is much more stout than a lot of code compliant accessory buildings, and not likely to compromise safety in any way.

accepted engineering practice should never be used on the construction drawings. As an engineer I do not understand what "accepted engineering practice" means.

 

[Mark K]

The supervisor is wrong but you want to keep your job. I would be VERY surprised if the supervisor was an engineer. Personally I believe all building officials be either an licensed engineer or a licensed architect.

It is possible for a part of the building to be designed by an engineer without requiring the whole building be designed by an engineer.. If some part of an existing building was engineered in a remodel would this mean the whole building be engineered and upgraded.? Where do the laws say I am wrong.

The focus should not be on whether an engineer sealed the drawings but on whether the design and what was constructed complied with the code.

Your immunity is with respect to your providing what is required by the code. If you decide to require more you are acting as a designer and you have no immunity when you are the designer.

 

[jod0001]

I would agree that in this case the code official screwed the pooch.

Just above I quoted our former State Building Inspector, who often stated in classes that "The code is the least you can accept and the most you can require."

That's true -- as far as it goes. But IMHO that's at the plan review level. Nothing in the code or in law prevents an owner or a designer from exceeding the minimum requirements of the building code. When we approve a set of construction documents, those plans and details become the minimum standard for that building. We should be inspecting to that standard. You used the footing as the example, but how about floor framing? A living room may meet the prescriptive requirements of the code with 2x10 joists, but the owner doesn't want bouncy floors so the designer called for the ground floor to be framed with 2x12s. I approve construction documents calling for the ground floor to be 2x12s. I should not allow 2x10s in the field even if they meet the code, since they don't match what's shown on the approved construction documents.

So when it comes to floor joist, ceiling joist beams and rafters many of the plans that we receive do not call out those items when using nominal lumber. With that being said with floor joists and beams, many contractors use Engineered Wood Products (EWP) We follow those down to the letter, we also verify the allowable drilling of the Ijoist, should they be over drilled (as describe in the manufacturer guidelines) mainly due to ductwork we advise the contractor we can not pass the EWP, until a letter of repair has been sent in to our office and the performed repair matches what is in the letter. We look at this during the framing inspection after all the trades have been completed and passed. During the framing inspection we also look at the truss system, those normally fail due to broken trusses, which also require a letter of repair, they also fail to stabilize the piggy back trusses. Other than that we verify the span length of the ceiling joist and rafter, if not a truss system. One other thing we look at is where their air handler is, if the air handler is sitting out over ceiling joist and not over a wall we will require that the ceiling joist supporting the weight of the air handler are sized as floor joist. I can’t quite recall the specifics verbiage in the mechanical code but it basically states that the framing should be sized to adequately support the equipment and workers, ceiling joist is sized for sheet rock where floor joist are sized for sheet rock and dead/live loads.

 

[jod0001]

The supervisor is wrong but you want to keep your job. I would be VERY surprised if the supervisor was an engineer. Personally I believe all building officials be either an licensed engineer or a licensed architect.

It is possible for a part of the building to be designed by an engineer without requiring the whole building be designed by an engineer.. If some part of an existing building was engineered in a remodel would this mean the whole building be engineered and upgraded.? Where do the laws say I am wrong.

The focus should not be on whether an engineer sealed the drawings but on whether the design and what was constructed complied with the code.

Your immunity is with respect to your providing what is required by the code. If you decide to require more you are acting as a designer and you have no immunity when you are the designer.

Yes, I feel if part of it is engineered design then we must follow it, if I choose not to enforce the design and what I allow fails then I own the failure, where as if I would enforce the engineer design and it still fails, we’ll I hope the designer has a good E and O policy.

 

[jod0001]

The supervisor is wrong but you want to keep your job. I would be VERY surprised if the supervisor was an engineer. Personally I believe all building officials be either an licensed engineer or a licensed architect.

It is possible for a part of the building to be designed by an engineer without requiring the whole building be designed by an engineer.. If some part of an existing building was engineered in a remodel would this mean the whole building be engineered and upgraded.? Where do the laws say I am wrong.

The focus should not be on whether an engineer sealed the drawings but on whether the design and what was constructed complied with the code.

Your immunity is with respect to your providing what is required by the code. If you decide to require more you are acting as a designer and you have no immunity when you are the designer.

He is not an engineer but although i disagree with him on the one aspect he is very knowledgeable of the code and structural aspects of building which can be both a good thing and a bad thing.

 

[Mark K]

Yes, I feel if part of it is engineered design then we must follow it, if I choose not to enforce the design and what I allow fails then I own the failure, where as if I would enforce the engineer design and it still fails, we’ll I hope the designer has a good E and O policy.

Talk with a lawyer to better understand your liability. If you limit your actions to enforcing the code you, as a building official, likely have no liability even if you make a mistake. But if you go beyond what is required by the code and act as a designer you likely will have liability

 

[steveray]

Personally I believe all building officials be either an licensed engineer or a licensed architect.

That helps when you are dealing with incompetent designers....Other than that, it is useless....

 

[Mark K]

That helps when you are dealing with incompetent designers....Other than that, it is useless....

How does a building official review the submitted engineering calculations if he had no engineering training? If the answer is that you only look at the engineers stamp then I suggest that you have not done your job.

 

[steveray]

How does a building official review the submitted engineering calculations if he had no engineering training? If the answer is that you only look at the engineers stamp then I suggest that you have not done your job.

I look at the design loads they designed to....and the stamp.....and If i see anything weird I will ask a question of the all powerful engineer that never makes mistakes...That is all my job requires me to do.....

 

[Yankee Chronicler]

That helps when you are dealing with incompetent designers....Other than that, it is useless....

No, it doesn't.

I'm an architect, wearing a building official hat. Been there, done that. Remember the old saying: "Ignorance can be educated. Stupid is forever."