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Lack of codes to force builders to build foundations suitable to questionble soils.

A

ahewett@uselman

Member
Joined
Jun 24, 2013
Messages
6
Location
New Mexico
I'm frustrated to see standard foundation design on questionable soils. We receive quite a few calls each year from homeowners for repairing standard foundation systems placed directly on expansive soils. I have researched residential code and found a very complex responsibility trail. Anybody have any input? I have tried talking to the local inspector about this subject, but I am not getting anywhere.

Here is a example.

The IRC 2009 R401.4 changes here in New Mexico, with an amendment, 14.7.3.12

• International Residential Code for One- and Two-Family Dwellings

o [ 2009 (Fifth Printing) ]

R401.4 Soil tests. Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting or other questionable soil characteristics are likely to be present, the building official shall determine whether to require a soil test to determine the soil's characteristics at a particular location. This test shall be done by an approved agency using an approved method.

New Mexico changes to IRC 2009

14.7.3.12 CHAPTER 4 FOUNDATIONS:

A. Section R401. See this section of the IRC except as provided below: Section R401.4 Soil tests. Delete the text of this section and replace with the following. Where quantifiable data created by accepted soil science methodologies indicate expansive, compressible, shifting, or other questionable soil characteristics are likely to be present at a particular location, a soil test to determine the soil’s characteristics at a particular location shall be performed.

This seems like the only code is to force testing. Cannot find a code direction to do anything with the soils report, if it was showing a poor soils condition.

I am also considering this line from IRC 2009 below. I cannot find the reference: 1805.8 of the 2009 IBC. 1805.4.3 Drainage discharge is the last entry in my copy of code for chapter 18. But it almost looks like IRC2009 - R403.1.8 tries to kick the problem up to the steeper requirements of commercial building code.

R403.1.8 Foundations on expansive soils. Foundation and floor slabs for buildings located on expansive soils shall be designed in accordance with Section 1805.8 of the International Building Code.

Exception: Slab-on-ground and other foundation systems which have performed adequately in soil conditions similar to those encountered at the building site are permitted subject to the approval of the building official. I hope some of this makes sense to somebody.
 
First, welcome the THE forum!

We've amended our local Code to require 2-#5 horizontal bars, top and bottom due to expansive soil.

My previous experience has been when a pre-excavation soil test, or the actual excavation reveals "questionable soil" the owner/builder/code official require an engineered design solution.

If your AHJ isn't requesting soil tests, responsibility falls on the builder. Doesn't really help future property owners though.

mj
 
The regional builder sells this homes with a 10 year structural warranty. I am dealing with the insurance company to attempt repair. They brought in their "experts". Experts did a soils test and wanted to compaction grout with concrete under footings/slab to firm up what they thought was just bad compaction of fill. I look at the soils report and see that there is a foot or two of fill on top of a 15 ' deep expansive clay. I see the compaction grout idea making things worse. My engineer agrees. The insurance company wants a quote to fix the drywall cracks, door resets and a little surface water redirection. Each lot has a septic tank, which makes things worse. I also am seeing questionable framing problems, ventilation and truss uplift. Owners of building are looking for a compliance issue that I cannot seem to find.
 
It feels like our local inspector thinks its not his responsibility to force a engineered design solution.
Click to expand...
Also, ..Welcome to the Building Code Forum!

The inspector is an arm of the AHJ! The AHJ is the entity to enforce or not enforce anything! It's

up to the adopted codes / policies of that AHJ to determine a compliance path here! This one

sounds like it is going to be real messy.

.
 
As you have found unless the building official has reason to believe no geotechnical report is needed the owner must provide one.

Once the geotechnical report is received the application for permit can/should be required to reflect the recommendations of the geotechnical report. If it does not there is no permit.

Because the IRC is supposed to be for simple buildings there are no provisions for expansive soils, thus the applicant is referred to the complementary and more general IBC to address the issue.

As far as the building code is concerned the building owner is responsible for everything. As a result the building owner hires architects, engineers, and contractors to help him fulfill his responsibilities. The building code is not intended to address problems between the building owner and the consultants and contractors he may hire.

Remember even if building official’s lack of action contributed to the problem the City/County will likely have no legal liability.

Your clients probably need the advice of a knowledgeable attorney. Litigation can be expensive and can drag on for years so everybody should try to be pragmatic about when to settle. Do not expect justice out of the legal system.
 
In my opinion and experience, the responsibility for the foundation performance lies with the builder, the design firm’s engineer, and the AHJ; but not necessarily in that order. I can only speak for Texas and not other states, but here all of the above entities can be held legally liable for foundation failure. The AHJ cannot fall back on the sovereign immunity doctrine.

Again, I am not sure what sort of foundation is in question, but the set of codified rules is almost the same for all foundations, save for prestressed post-tensioned. First the IRC, which then defers to the IBC. Beyond these two come all of the referenced standards that apply to the particular type of foundation. These can include those promulgated by the American Concrete Institute, the Wire Reinforcement Institute, the Post-Tensioning Institute, the Building Research Advisory Board, et al.

All foundations built on expansive soil must be of an engineered design. All foundations built on expansive soil must be designed according to geotechnical engineer soil borings from the site in question. The design engineer is required to refer to these soil test reports and design the foundation accordingly. It is the engineer’s responsibility to design a foundation that will withstand the forces of supporting soils.

Assuming for a moment that the foundation was properly designed, then any failure of the foundation can only be attributed to either inadequate or defective materials, or faulty installation; or an act of God, which is not the topic of this post. It is the responsibility of the builder, the contractors under his supervision, and the AHJ who oversees all to insure that the materials and workmanship are code-compliant.

In my experience, foundation failure is almost always the result of under-engineering. This is, of course, driven by the homebuyer’s, and thus the builder’s, desire to save money. Because foundations on expansive soil lie exclusively in the purview of the design engineers, the AHJs bear little if no responsibility, save that of insuring that the code has been adhered to in every respect.
 
Mercifully, here, the jurisdiction has mapped bad soil and shows it on their property verification system. If the inspector leaves the site, on a rainy day, taller than they arrived.. the soil is questionable.
 
peach,

I like that you have had bad soils mapped, thats a very usful tool. I have to use the soil survey maps here from 1985. Was that done by your engineers?

pc1
 
I would think that this would go back to engineering. You should have had and engineering firm complete a soils report for the subdivision. Then there should have been an excavation observation to determine that all conditions of the soils report were met. This would include all required compaction results/observations if required. Then the engineer would have to design the foundation which that design would be followed with out additional requirements.
 
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