Precast foundation system

[philmck]

Please forgive my ignorance on the subject matter, and if this is not the proper arena for this neophyte type question, but I am a ChemE seriously outside his area of expertise. I am about to purchase a home with a "superior walls" precast foundations system. I have done my research on the web but all that is out there tends to be "you got to have it" type propaganda. The system does not have a footer akin to the traditional poured wall construction. The precast panels are laid on compacted crushed stone with an outside perimeter drain tile. Without a footer how does the overturning moment from the lateral load get taken out? Are there any chronic/systemic problems that I should be aware of with these type of foundations in the residential home building industry? I am just trying to get the warm fuzzy feeling before this substantial investment.
Thank you in advance, Phil

 

[haggis]

I may not be of much help here as (1), I have never heard of this system and (2), I am neither structural or geotechnical in my expertise.

I do however, have some expeirience with small structures i.e. houses. When you mention footer, I presume you mean the traditional strip footing at the bottom of the wall.

If these precast walls are (presumably) 10" to 12" thick, how are the vertical loads of the building being dispersed.

As I said, not much help but am surprised nobody responded to your post.

Good luck,

Haggis

 

[dicksewerrat]

I guess I'd have ageotech. Engr look at the plan and the soils and give you an opinion. W
ill this bldg. stay there or slowly sink into the earth? How does the floor tie to the walls?

 

[pmkPE]

Q: What are the components of the Superior Walls system?
A: Superior Walls panels are created in a factory, where high-strength 5,000+ psi concrete is formed directly to DOW ® insulation. Solid concrete studs provide support, as does a built-in concrete footer that rests on a sub-footer of clean crushed stone. The attention to detail is evident in features that make finishing basements easy, such as pre-engineered wiring access holes and furring strips for easy drywall installation.

I copied the above from the manufacturer's web site. Apparently there is some sort of footer as per their advertisement. If you review the IBC 2000 building code for residential construction it is acceptable to have a wall type structure bearing directly on the sibgrade without the typical footer. However, the basis for such design should be based on geotechnical evidence that there is adequate bearing capacity for the "narrow" wall bearing on the specific soils at your site.

 

[AlohaBob]

How long are the panels? Are the panels joined together with shear connections to mitigate differential settlement between panels?

If the shear connections aren't there, I wouldn't touch it.

 

[philmck]

Panels are approximately 10 feet long. The seams in between the panels are filled with a flexible polyurethane seal. There are shear connectors. I called the local building inspector and asked him on the history of this system in the area. He reported that they have been installing these walls for approximately 8 years and as far as he knew there were no issues. I plan still to buy some time from a local geotech engineer. Phil

 

[AlohaBob]

With the shear connections being substantial, the foundation should act as a tremendously stiff rigid body. The axial loads from a residential structure are relatively small compared to the capacity of a precast foundation to redistribute that load in a uniform manner to the soil. I would place my bet alls well.

If you still have doubts....Call 1-800-XYZ-Structural-Engineer. He can model the loads and connections, approximate the soil bearing characteristics, apply all required applicable loads, and even experiment with some what ifs. Have him make a report and predict - describe the envelope scenarios and probable failure mechanisms. Compare these with actual and prescribed loads.