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Mobile Homes

Plumb-bob

Registered User
Joined
Aug 31, 2022
Messages
214
Location
BC
How do you guys deal with modifications to mobile homes? I have been struggling with this for some time, and have come to the conclusion that these creatures are outside of the building code and any structural modifications must be engineered. But most of the local engineers dont want to touch them, so it leaves the owners in a tight spot.
 
I would disagree that they are outside of the code. They take advantage of certain exceptions or alternative path to code compliance in comparison with traditional construction. A good example being 9.15.1.3. allowing them to be blocked under CSA Z240, rather than on a traditional foundation.

A lot of them are engineered, but I'm not sure I could agree that this would required any additions to be engineered unless they violated the original engineered design assumptions.

Whether it is stamped or not, if the building is compliant under Part 9, we can use Part 9 for additions or modifications that fall under the jurisdiction of Part 9.
 
Minihomes are not exempt from Code. They are deemed code-compliant from the factory (CSA A277), and once placed in situ are essentially Code-compliant buildings. BCBC has language for "altering" a building, just as NBC does.
You have a Part 9, C occupancy single-family dwelling. Altering it or adding to it must adhere to Part 9 (or part 4) like any other building.
Mobile homes (that being the old style things on wheels, but difficult to move) are still structures. They are likewise subject to Code.

The only potential exception I would consider is that most of those homes are on blocking per (as tmurray noted)Z240 10.1. We allow small additions (porches, decks) attached to Z240 10.1 structures to have foundations at grade, since a blocked minihome may move with frost, and having foundations for a deck would create a differential movement.
 
I would disagree that they are outside of the code. They take advantage of certain exceptions or alternative path to code compliance in comparison with traditional construction. A good example being 9.15.1.3. allowing them to be blocked under CSA Z240, rather than on a traditional foundation.

A lot of them are engineered, but I'm not sure I could agree that this would required any additions to be engineered unless they violated the original engineered design assumptions.

Whether it is stamped or not, if the building is compliant under Part 9, we can use Part 9 for additions or modifications that fall under the jurisdiction of Part 9.
I have a hard time understanding this. These units are factory built and certified, not built to Pt9 in any way, including structure, insulation, foundations etc.

The situation I have in front of me today is an old trailer that is gutted and being rebuilt. I found it at this stage and placed a stop work order on it. Much of the structure is rotten, including floor members, sheathing, studs and top plates. If I were to allow the owner to rebuild it to the original state then I am allowing 2x3 framing members, low insulation values etc., at which point I will be inspecting and certifying a standard that I have no business certifying.

If I require the rebuild to be to Pt9 then the entire structure will change, but still be supported by a rusty metal frame, which I cannot assess for being able to withstand the loads imposed by code compliant framing.
 
Minihomes are not exempt from Code. They are deemed code-compliant from the factory (CSA A277), and once placed in situ are essentially Code-compliant buildings. BCBC has language for "altering" a building, just as NBC does.
You have a Part 9, C occupancy single-family dwelling. Altering it or adding to it must adhere to Part 9 (or part 4) like any other building.
Mobile homes (that being the old style things on wheels, but difficult to move) are still structures. They are likewise subject to Code.

The only potential exception I would consider is that most of those homes are on blocking per (as tmurray noted)Z240 10.1. We allow small additions (porches, decks) attached to Z240 10.1 structures to have foundations at grade, since a blocked minihome may move with frost, and having foundations for a deck would create a differential movement.
By allowing foundations that are not frost protected you are immediately outside of Pt9.

Many of the additions to mobiles that i see have substantial air leakage into the walls and roof, resulting in mould.

I believe these units lose their A277 certification if they are altered, leaving them in some grey zone.

As a side note, I would guess that 1/2 of the fires we get in our small town are in mobile homes, which make up at most 5% of the housing stock.
 
If they are factory certified, wouldn't you need to ask them to have a factory certified inspector review their changes to the mobile and re-certify it? If they can't provide that then it would need to meet all codes as if it were an existing (old) structure being brought up to current codes.
 
I have a hard time understanding this. These units are factory built and certified, not built to Pt9 in any way, including structure, insulation, foundations etc.

The situation I have in front of me today is an old trailer that is gutted and being rebuilt. I found it at this stage and placed a stop work order on it. Much of the structure is rotten, including floor members, sheathing, studs and top plates. If I were to allow the owner to rebuild it to the original state then I am allowing 2x3 framing members, low insulation values etc., at which point I will be inspecting and certifying a standard that I have no business certifying.

If I require the rebuild to be to Pt9 then the entire structure will change, but still be supported by a rusty metal frame, which I cannot assess for being able to withstand the loads imposed by code compliant framing.

No different than issuing a permit to rebuild home that was constructed in the 1970s, with 2x4 walls, etc.
We have a number of renos to buildings constructed in the 1880s! Sure as heck, not to any Code ever considered.
NBC A1.1.1.1(1) gives guidance: try to get the renovated home as close to existing codes as reasonable/practicable. Internal office policies will assist greatly in creating some certainty. In our case, if we have a project where the building is being gutted to the exterior studs, we require R17 insulation in the walls wherever practicable, vapour barrier to Code, an HRV, etc. It doesn't mean you make the renovator push *everything* to Code, but you push for what's practicable.

Rebuilding the stair? If you can get a NBC2015 stair - 10" runs - in the same space, great. If not, as long as the new stair provides at least the same run as before, you're being reasonable. (Canlii has a number of good decisions to give guidance - search "building inspector" + "reasonable" for examples.)

2x3s can legally serve as load-bearing framing members in NBC2015.

Canadian Wood Council allows one-ply lintels, FYI. Suitable for framing openings in 2x3 construction.
 
I don't know how you guys do mobile homes up there, so I will defer to the Canadians on this one.

Down here, mobile homes are under federal regulations, and the state of Kansas has really limited our ability to address items with mobile homes from a municipal level. The homes are outside of a lot of prescriptive codes we use, so we generally have to get engineers involved.
 
No different than issuing a permit to rebuild home that was constructed in the 1970s, with 2x4 walls, etc.
We have a number of renos to buildings constructed in the 1880s! Sure as heck, not to any Code ever considered.
NBC A1.1.1.1(1) gives guidance: try to get the renovated home as close to existing codes as reasonable/practicable. Internal office policies will assist greatly in creating some certainty. In our case, if we have a project where the building is being gutted to the exterior studs, we require R17 insulation in the walls wherever practicable, vapour barrier to Code, an HRV, etc. It doesn't mean you make the renovator push *everything* to Code, but you push for what's practicable.

Rebuilding the stair? If you can get a NBC2015 stair - 10" runs - in the same space, great. If not, as long as the new stair provides at least the same run as before, you're being reasonable. (Canlii has a number of good decisions to give guidance - search "building inspector" + "reasonable" for examples.)

2x3s can legally serve as load-bearing framing members in NBC2015.

Canadian Wood Council allows one-ply lintels, FYI. Suitable for framing openings in 2x3 construction.
I can see the logic. But for the big picture, I do not think these units were ever intended to be altered, and as soon as they are they become something else. On the flip side, they provide much more affordable housing than SFDs so fulfill a valuable niche.
 
By allowing foundations that are not frost protected you are immediately outside of Pt9.

Not necessarily: See NBC 9.12.2.2 (table) for required foundation depths. Footings need not be at depth for coarse, well-drained soils.
That's what we use as guidance when allowing foundations-at-grade for small additions (decks/porches) to Z240-compliant buildings on blocks.
 
Well drained soils to below frost depth are frost protected, at least per ASCE 32. It's pretty strict on how little fines you can have.
 
I have a hard time understanding this. These units are factory built and certified, not built to Pt9 in any way, including structure, insulation, foundations etc.

The situation I have in front of me today is an old trailer that is gutted and being rebuilt. I found it at this stage and placed a stop work order on it. Much of the structure is rotten, including floor members, sheathing, studs and top plates. If I were to allow the owner to rebuild it to the original state then I am allowing 2x3 framing members, low insulation values etc., at which point I will be inspecting and certifying a standard that I have no business certifying.

If I require the rebuild to be to Pt9 then the entire structure will change, but still be supported by a rusty metal frame, which I cannot assess for being able to withstand the loads imposed by code compliant framing.
Are these buildings exempted from the code by your province's building act? If not it must be built to code. If they are exempt from the code, modifications would be exempt as well. Your review would be limited to the addition.
 
CSA A277 under section 4.1 requires these buildings comply with "the National Building Code of Canada or the applicable provincial, territorial, or municipal building code;"
 
Are these buildings exempted from the code by your province's building act? If not it must be built to code. If they are exempt from the code, modifications would be exempt as well. Your review would be limited to the addition.
Not exempted from the code, just not Pt9
 
Not exempted from the code, just not Pt9
Do you have a code reference? I'm not familiar with anything that would preclude these buildings from using Part 9 as a compliance path.

The A277 only requires an engineer for commercial, semi-commercial, and industrial factory constructed buildings.
By allowing foundations that are not frost protected you are immediately outside of Pt9.
See 9.15.1.3. for a reference to CSA Z240.10.1. as an acceptable foundation type for these buildings.
 
A277 is a certification standard, not a building code.
Z240 is the actual building code for mobile homes.
From the BSSB:

1681422208951.png
So to apply Pt9 to these buildings seems to me a stretch. And because I live in a swamp with clay soils that are very prone to frost jacking, there is always differential movement between trailers and additions that leads to mould from either bulk water entry or air barrier failure.
 
A277 is a certification standard, not a building code.
Z240 is the actual building code for mobile homes.
From the BSSB:

View attachment 10496
So to apply Pt9 to these buildings seems to me a stretch. And because I live in a swamp with clay soils that are very prone to frost jacking, there is always differential movement between trailers and additions that leads to mould from either bulk water entry or air barrier failure.
OK, so with exception of foundations, siting, and mountings, these buildings are exempt from the BC code.

That is a BC specific amendment to the code and does not exist in either the national code or the Ontario code (the only other two I own).

We should differentiate between the CSA 240.2.1 (structural requirements) and the CSA 240.10.1 (site anchorage). It appears that the structural requirements are dealt with differently between our codes.

The CSA Z240.2.1 that deals with structural requirements is not referenced at all by the national code and only referenced in Part 3 for the Ontario code. The BC code does reference it is Part 9 through.

Now we are a little bit better equipped to answer the original question: can modifications happen to these buildings? Yes, provided the modifications comply with CSA Z240.2.1.

Here is the national commentary on factory constructed buildings (A-1.1.1.1.(2)):

A-1.1.1.1.(2) Factory-Constructed Buildings. The NBC applies the same requirements to site-built
and factory-constructed buildings. However, it can often be difficult to determine whether a factory-constructed
building complies with the Code once it has been delivered to the construction site because many of the wall,
roof and floor assemblies are closed in and so their components cannot be inspected. CSA A277, “Procedure for
certification of prefabricated buildings, modules, and panels,” was developed to address this problem with
regard to residential, commercial and industrial buildings. This standard describes a procedure whereby an
independent certification agency can review the quality control procedures of a factory and make periodic
unannounced inspections of its products. The standard is not a building code, only a procedure for certifying
compliance of factory-constructed components with a building code or other standard. If a factory-constructed
building bears the label of an accredited certification agency indicating that compliance with the National
Building Code has been certified using the CSA A277 procedure, the accepting authority will have some
assurance that the concealed components do not require re-inspection on site.

On the other hand, standards in the CSA Z240 MH Series, “Manufactured homes,” do resemble a building code.
Most of the individual standards in the series contain requirements regarding many issues also covered in the
NBC. Some of these Z240 MH Series provisions are performance requirements with no quantitative criteria,
some simply reference the applicable NBC requirements, while others contain requirements that differ from
those in the NBC. Because it would be illogical to have two different sets of requirements for buildings—one set
that applies to site-built buildings and one set that applies to factory-constructed buildings—the NBC does not
reference these Z240 MH Series standards. One of the individual standards in the Z240 MH Series deals with
special requirements for manufactured homes related to the fact that these houses must be moved over roads,
which is an issue the NBC does not address. Therefore, labeling that indicates that a factory-constructed house
complies with the Z240 MH Series standards can NOT be taken as an indication that the house necessarily
complies with the building code in effect for the location where the house will be sited.

The NBC does reference CSA Z240.10.1, “Site preparation, foundation, and installation of buildings,” which is
not actually part of the CSA Z240 MH Series. This standard contains requirements for surface foundations
where buildings—not just houses—comply with the deformation resistance test provided in CSA Z240.2.1,
“Structural requirements for manufactured homes.”
 
I agree that a modification that complies with the Z240 would be appropriate, but I feel I am not equipped to approve work to this standard. I believe to do work to this standard you must have a facility that has the A277 certification.
Also, a large part of the intent of the Z240 is to keep these structure road worthy, and any form of alteration or addition obviously compromises this ability. And this can have implications for zoning and other bylaws regarding a "mobile home" park.
Anyways, I appreciate the comments, they have been helpful.
I decided to go down the rabbit hole on this because of the poor state that many of our mobiles are in, and the rash of fires (including a fatality) that we have had over the past several years. I love seeing the old shitty trailers getting replaced with nice new ones.
 
The rules in the states are different from those in Canada.. The Federal government is involved because the mobile homes are assumed to be able to travel between the states. I believe that state jurisdiction is limited to issues related to foundation and bracing issues. Decks would be subject to local codes.
 
I really had to question my understanding of this several times, and now feel I understand the issue better than before. So time well spent.

FYI the snip I posted is not out of the BCBC, but is a bulletin from the Building Safety and Standards Branch, which is provincial, which explains the difference in the approach between provinces.
 
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