Isolated pier foundations for manufactured buildings

[Sifu]

Can a manufactured building regulated by the IBC be supported on isolated footings and piers without a continuous exterior footing? For example, a light-frame wood, with exterior bearing walls supported by exterior floor beams spanning between isolated footings and masonry piers, with a non-structural "skirt"?

 

[fatboy]

If it were a stamped engineered design, I don't see why not.

 

[classicT]

See it all the time here. Typically still have some non-structural skirting at the perimeter. The isolated footings still have to extend to frost depth.

And make sure the geo-engineer is aware. Locally, they typically require larger pads due to the sliding potential.

 

[Mark K]

What code provision would prevent it?

 

[bill1952]

If it were a stamped engineered design, I don't see why not.

I can see the IRC could be interpreted differently I have built several permitted additions on independent piers with beams, without a RDP seal. R403.1 (2018) starts with "continuous solid or fully grouted masonry or concrete footings" but goes on to allow "other approved structural systems". Does the code or do you require an engineer for "other approved"?
R403.1.3.6 and R404.1.9 seem to permit prescriptively isolated concrete and masonry piers supporting floor beams for both interior and exterior walls.

So educate me as to why what the OP asks is not permitted without a RDP sealed drawing?

 

[Sifu]

Agree with what everyone is saying, but I was asked some specific questions about it yesterday....to which I said, "if its engineered", and "its done all the time", and that I knew of no code that prohibits it. But in double checking my assumptions I don't see where it is permitted if its engineered (the normal "designed in accordance with accepted engineering practice") but I do see that shallow foundations must satisfy 1809, and the only language that looks close is 1809.10 for pier and curtain wall foundations. Isolated footings don't satisfy item #1. However, if a bearing wall is supported by a beam, and that beam is supported by an isolated pier, I am not placing a load bearing wall on a footing, thereby negating item #1? If I get past item #1 then I am left with item #3 only and it works. That is the assumption I made years ago in residential, but now I need to check my assumptions.

 

[Sifu]

I can see the IRC could be interpreted differently I have built several permitted additions on independent piers with beams, without a RDP seal. R403.1 (2018) starts with "continuous solid or fully grouted masonry or concrete footings" but goes on to allow "other approved structural systems". Does the code or do you require an engineer for "other approved"?
R403.1.3.6 and R404.1.9 seem to permit prescriptively isolated concrete and masonry piers supporting floor beams for both interior and exterior walls.

So educate me as to why what the OP asks is not permitted without a RDP sealed drawing?

I was looking for the same type of language as the IRC for "other approved" systems but couldn't locate it. The only prescriptive language in shallow foundations says "where a specific design" is not provided, table 1809.7 can be used, but that still refers back to required foundation walls. I am not sure what "specific design" means in this case anyway. I assume it means engineered design, but then why not use the same language used in most other similar situation of "accepted engineering practice"?

 

[bill1952]

I was looking for the same type of language as the IRC for "other approved" systems but couldn't locate it. The only prescriptive language in shallow foundations says "where a specific design" is not provided, table 1809.7 can be used, but that still refers back to required foundation walls. I am not sure what "specific design" means in this case anyway. I assume it means engineered design, but then why not use the same language used in most other similar situation of "accepted engineering practice"?

Probably my confusion about which code includes what buildings. It seemed like purely an IRC question but I guess in other parts of the country, there are other modular buildings than manufactured homes.

It sounds as if you would accept isolated piers supporting beams supporting walls for a one or two family dwelling without RDP seals?

 

[Sifu]

The IRC clearly allows an engineered design in lieu of continuous footings, and I had many arguments about 15 years ago when I would inform people that their footings needed to be continuous or to get an engineer. But that wasn't required for manufactured foundations, I just can't recall how or why. Back then we had an actual manufactured housing code, but I can't find it now.

Probably my confusion about which code includes what buildings. It seemed like purely an IRC question but I guess in other parts of the country, there are other modular buildings than manufactured homes.

It sounds as if you would accept isolated piers supporting beams supporting walls for a one or two family dwelling without RDP seals?

Doubtful. Lateral load path would give me pause. But all day long with an engineer, but my question isn't if it can be done without an engineer, rather if it can be done with an engineer for a commercial building.

 

[Sifu]

I found my old code from a different state, which offers prescriptive requirements for isolated footings for manufactured housing, so now I know why I remember dealing with it. But it still doesn't answer the non-residential question.

 

[Sifu]

I have seen many, and approved a few, modular classrooms with isolated foundations, engineered systems on metal or masonry piers and anchoring systems without a continuous foundation, now I'm just concerned about the justification. So many out there, I know there must be a codified path. I know the code doesn't appear to prohibit it directly (no "shall nots") but the " shall" requiring compliance with 1809.2, seemingly without specific provisions for these foundations is making me dig a little deeper.

 

[classicT]

The word "continuous" does not even appear in Section 1809 Shallow Foundations.

Not sure what you are digging for... conventional isolated pier pads, just like a continuous perimeter footing, are shallow foundations.

 

[Sifu]

The word "continuous" does not even appear in Section 1809 Shallow Foundations.

Not sure what you are digging for... conventional isolated pier pads, just like a continuous perimeter footing, are shallow foundations.

1809.10 Pier and curtain wall foundations. Except in Seismic Design Categories D, E and F, pier
and curtain wall foundations shall be permitted to be used to support light- frame construction not
more than two stories above grade plane, provided that the following requirements are met:
1. All load-bearing walls shall be placed on continuous concrete footings bonded integrally with
the exterior
wall footings.

A shallow foundation must comply with 1809.2 through 1809.13, a pier and curtain wall system is permitted to be used and since no other provision seems to account for isolated piers that is the closest provision in these sections I can find.

 

[steveray]

I can see the IRC could be interpreted differently I have built several permitted additions on independent piers with beams, without a RDP seal. R403.1 (2018) starts with "continuous solid or fully grouted masonry or concrete footings" but goes on to allow "other approved structural systems". Does the code or do you require an engineer for "other approved"?
R403.1.3.6 and R404.1.9 seem to permit prescriptively isolated concrete and masonry piers supporting floor beams for both interior and exterior walls.

So educate me as to why what the OP asks is not permitted without a RDP sealed drawing?

This gets a little contentious in the IRC:

R602.10.9 Braced wall panel support. Braced wall panel
support shall be provided as follows:
1. Cantilevered floor joists complying with Section
R502.3.3 shall be permitted to support braced wall
panels.
2. Raised floor system post or pier foundations supporting
braced wall panels shall be designed in
accordance with accepted engineering practice.

 

[Sifu]

This gets a little contentious in the IRC:

R602.10.9 Braced wall panel support. Braced wall panel
support shall be provided as follows:
1. Cantilevered floor joists complying with Section
R502.3.3 shall be permitted to support braced wall
panels.
2. Raised floor system post or pier foundations supporting
braced wall panels shall be designed in
accordance with accepted engineering practice.

I KNEW THAT WAS IN THERE SOMEWHERE! I just couldn't find it.

 

[bill1952]

Thanks for finding this. Feels like there's a grammar problem but seems a little vague.

R602.10.9 Braced wall panel support. Braced wall panel support shall be provided as follows:

2. Raised floor system post or pier foundations supporting braced wall panels shall be designed in accordance with accepted engineering practice.

Not clear if it is the floor system or floor system 'on' post or pier foundations or just the post or pier foundation that needs an RDP. I should look for commentary.

 

[Mark K]

I can see the IRC could be interpreted differently I have built several permitted additions on independent piers with beams, without a RDP seal. R403.1 (2018) starts with "continuous solid or fully grouted masonry or concrete footings" but goes on to allow "other approved structural systems". Does the code or do you require an engineer for "other approved"?
R403.1.3.6 and R404.1.9 seem to permit prescriptively isolated concrete and masonry piers supporting floor beams for both interior and exterior walls.

So educate me as to why what the OP asks is not permitted without a RDP sealed drawing?

There are two distinct questions compliance with the IRC and whether an engineer is required. The answer may vary for different states. It is your state licensing laws, not the building code, that determine when an engineer is required.

 

[bill1952]

There are two distinct questions compliance with the IRC and whether an engineer is required. The answer may vary for different states. It is your state licensing laws, not the building code, that determine when an engineer is required.

I think in my rural area it's the building official that determines that.

 

[Mark K]

"Accepted engineering practice" is a poorly defined term.

The IRC has a provision that allows the use of the IBC when dealing with conditions not addressed in the IRC.

 

[Mark K]

I think in my rural area it's the building official that determines that.

Unless your state statutes are explicitly clear that the building official can determine when an engineer is required I suggest you think again.

The licensing of engineers restrains trade and would be subject to the federal anti-trust laws except when the state legislature, not the city council or the building official, has clearly articulated a desire to restrain trade. The US Supreme Court made this clear. Thus if the local jurisdiction decided to regulate when an engineer was required they would be subject to anti-trust legislation.

 

[fatboy]

"Can a manufactured building regulated by the IBC"

This is what I was responding to, and "exterior bearing walls supported by exterior floor beams spanning between isolated footings and masonry piers"

So, my assumption, take that FWIW, was this was a commercial structure, as the OP call it a manufactured building. We have many in our AHJ.

 

[Sifu]

"Can a manufactured building regulated by the IBC"

This is what I was responding to, and "exterior bearing walls supported by exterior floor beams spanning between isolated footings and masonry piers"

So, my assumption, take that FWIW, was this was a commercial structure, as the OP call it a manufactured building. We have many in our AHJ.

Yes, a proposed bank. And the building is manufactured but the foundation must be designed from the IBC.

 

[fatboy]

Yes, a proposed bank. And the building is manufactured but the foundation must be designed from the IBC.

Hence my reply.

 

[Genduct]

I think, The choice of foundation design to hold up a structure is not the key to this question but if the Structure in question falls under the Building Code or the DOT for Manufactured Housing.

Not sure why we are in a rut over traditional spread footing design as the only approach. I know we can tend to be creatures of habit, bur Piers have been used forever