Settlement - New 2 story Home & Analysis of Wall Foundation 3

[PT999]

I am looking at new home, with cracks in gypsum wall board, windows and door binding up, cracks in basement concrete floor slab, but no crack visible in 8" concrete foundation wall.

Still, I am concluding settlement of the wall foundation. How can I prove it conclusively. How can there be settlement without a crack in a foundation wall?

Secondly, regarding the unreinforced concrete wall foundation. I suspect the wall is to thin for the wall height which is 1 foot higher than the usual 8 or 8.5 ft (Total Height is 9.5 ft, concrete is supposed to be 3000 psi, will be tested shortly because of the cracked floor slab)

Exactly how is unreinforced concrete analyzed. Naturally all my texts and meager skills are for reinforced concrete design.

 

[pmkPE]

Obtain a copy of the NRCS (Formerly the SCS) Soil Survey for the county the structure is in. They, the manuals,are free (call the USDA in your local phone and loom for either SCS or NRCS). Locate the soil series that the structure is located on and search the tables for the estimated soil type. The tables will tell you if they are sandy, clayey, silty and to what percent plastic. Depending on these results choose your lateral soil pressure accordingly. Review your college soil text book(s), buy engineering/text book(s) on foundation design, join the local brach of the ASCE and/or the NSPE and talk with other engineers that are involved with residential type engineering problems. Consult the local governing authoruty that approves residential construction. What do they recommend as minimum values; what have they seen in the neighborhood that the structure is located in. Talk to locals........

 

[CSEllc]

PT999,

I'm from CT and our soils are usually similar. I have had numerous (many......spelling is not my strong suit) geotechnical reports done for various projects. Typically, the geotechnical engineers suggest a lateral fluid pressure between 50 to 60 pcf for restrained foundation walls since you must use the at rest pressure not the active pressure. The value will vary based on your site conditions, but this has been my experience with "free draining backfill"

If you look in the NYS Building Code in Chapter 18, they list varying backfill hieghts for various wall thicknesses. But, I doubt these thicknesses were actually "designed". I believe they are empirirical. I could be wrong, I haven't taken the toime to actually analyze the walls listed.

 

[engrx2]

In the Midwest, the standard is 8 inch with 1 no. 5 top and btm and no vertical reinf for a 8ft high basement wall. Walls over 8ft are typically 10 inches thick. Most times, it's difficult to get the values to check out if struct. calcs are required.