House trailor foundation 2

[rittz]

Does anyone have any details for a foundation for a Mobile home (mobile home park) like “permanent/temporary ( …I jest)

I see nothing about it in the NBCC (National Building Code of Canada) – 2005 …. (2010 out now but not in widespread use yet)

I have heard of the use of piles and grad beam (kinda permanent) and some also some sort pad and post setup c/w a cable and screw anchor … to keep it from blowing away !

The building inspector has advised the owner ( who wants to plunk it down on some plank pads) that the foundation has to be certified by an Engineer (good idea)

 

[Ron]

Most common foundation system in wind areas is to use soil anchor tie-downs. You can set the frame on anything you like, but when you compute overturning moment, you'll need some extra help from the soil anchors.

 

[rittz]

It would seem that one would need more than individual pads or a raft slab which essentially are bearing on existing grade. The manufactured mobile home should be capable of resisting differential settlement or frost heave. I could see the home moving up and in plastic clay or in deep freeze/thaw situations like here on the Canadian prairies.

 

[Ron]

Set the frame on piers extending below the frost line, then provide soil anchors in addition to handle uplift/overturning. Soil anchors should obviously extend below frost line.

 

[dik]

What area of Canada? What frost penetration and what type of soil?

Dik

 

[msquared48]

What are you worried about?

After all it is a "Mobile" Home. It's supposed to move!

The Mobile home manufacturer should have the foundation and tiedown instructions in the manual that came with the home, if the owner has it. Just carry it below frost.

Mike McCann
MMC Engineering

 

[rittz]

The frost penetration varies depending on the soil type. 4 ft to 6 ft +. Typically we use 5 ft here on the western prairies of Canada
A mobile home is supposed to be moved yes... but if it is not wrack resistant differential settlement of individual piers would damage the building.
Heaving of highly plastic clay results from seasonal volume changes (heaving and subsidence i.e. expansion due to increase in moisture content and settling due to drying). ..... more serious actually than changes due to frost.
The Owner would like to set in on the grade ... circumstances listed above (and possibly Codes) could dictate otherwise.

 

[a2mfk]

In the US there are federal guidelines and they are rather extensive regarding both temporary or mobile homes, and manufactured homes (not site built), which are two completely different categories. I would imagine you will have something similar way up north up der...? In the US, well at least not in Florida, this is not part of the building code. Manufactured homes must meet all the same requirements as any other structure in the regular building code, though in my experience they are riding that line pretty tight at times...

 

[Ron]

a2mfk....

In Florida, manufactured homes themselves are not under the building code. Any site built additions or appurtenances must comply with the building code, but the mobile home itself has to comply with HUD standards as you noted for the Federal requirements.

Florida has supplemented these requirements to accommodate anchorage for high winds.

It was interesting to see that 30 or so years ago, anchorage of mobile homes was from the frame to the ground. That didn't work, since wind would just blow the weak walls away from the transport frame (which we could then buy and make some terrific utility trailers). Then came the requirement that anchors would incorporate the roof as well. Still doesn't work when the winds get high.

 

[rittz]

It sounds to me that the codes you quote are not much interested in surface nounted pads with screw anchors for lteral support, but rather are treating them the same as a regular residential buildings requireing foundarions below the frost line. Yet megsa such surface foundations are in use for this type of structure

 

[GTEngineer95]

I run into this problem frequently (in Georgia) because FHA or other guaranteed loans require permanent foundations for loan approval. HUD document "7487 Permanent Foundations Guide for Manufactured Housing" has several methods for permanent anchorage, but soil anchors is specifically excluded. We pass on inspecting anything existing now because it never meets the requirements, and no one will pay for an engineered design for a new installation. Hope this helps.

 

[msquared48]

Plus, mortgage agents want the structural engineer to state that the existing meets the requirements of the HUD manual when the document specifically says that if the current condition is OK with the local jurisdiction, outside of the opinion of any structural engineering consultant, mine you, then no changes need to be made.

The financeers will not accept this out for the owner for existing mobile homes, and in this is the problem. They want the engineer to accept all of the responsibility and liability, not them, and we are painted as the bad guys when the loan fails. Go figure.

I, too, have stopped doing any of these for exactly that reason. I have enough situations where I have to be the bad guy. This is not one of them.

Mike McCann
MMC Engineering

 

[dik]

Depending on the soil type, construction can be a stiffened slab on grade for drained granular material and insulated as required for other soils with a perimeter foundation 'knee' wall of concrete or CMU's secured together so there is no overturning.

It is also possible to construct a frost wall either of concrete or masonry on a perimeter strip footing.

Both can be insulated and provide a crawlspace.

Alternatively, it's possible to construct the perimeter support using gradebeams and friction piles or some other type of piling.

Most areas of the prairies that I've done work in, frost penetration is typically 6' min...

Dik

 

[rittz]

NBCC Canada 9.12.2.2 6) b) permits a slab on grade for mobile homes (that is no foundation to the frost line) if the superstructure conforms to the requirements of the Deformation to Resistance test in CAN/CSA-Z240.1, “Structural Requirements for mobile homes”. And for other buildings less than 55 sq meters in building area.

This is presumably to guard against differential vertical movement causing damage to the superstructure.