Structural Inspection of Residential 4

[rlflower]

Perhaps several of you have conducted structural evaluations and/or inspections of residential construction. This subject is of interest to me in light of recent events highlighted on previous posts.

A couple of questions I would like to present here:

1.) Should there be general mandatory inspections required for structural elements of residential structures, regardless if they are privately owned or rented? How often should these inspections occur?
2.) In lieu of general mandatory inspections, should there be mandatory inspections of specific structural features of residential structures - and if so - what specific features should be inspected? And how often?

In absence of such required inspections, owners are left to their own judgement as to when to call for an evaluation. Usually, they do not call until disaster strikes. We get calls now and then from homeowners insurance companies for structural evaluations of residences that have recently been damaged. We also get calls from time to time from realtors regarding residences currently under escrow that have had a general inspection but required a "specialist" - in this case, a licensed engineer - to answer specific concerns.

Is it sufficient to leave the homeowner to his/her own devices, not really knowing when a certain situation could be dangerous, even life-threatening?

What are your thoughts on this?

Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.

 

[Jerehmy]

Seems like a lot of liability to say that an existing house is "structurally sound". The amount of time required to be sure of this would make an home owner balk at the price. Not only that, but a lot of residential framing is prescriptive design and doesn't really calc out which is something the forum talks about from time to time. A lot of roofs have been standing for 100 years (2x6's @ 24" oc anyone?), yet don't calc out. How do you put your liability on that?


I thought of becoming a home inspector on the side for some extra cash. I looked into how to get certified, pretty simple process. Pay a membership fee, get 100 hours experience, and take a test. Bam, certified.

I've seen some catastrophic failures of homes/garages for insurance companies. But it's always something the homeowner knows about and neglects.

 

[Ron]

Different rules, different design perspective, no consistency....that's residential.

Residential inspections during construction vary all over the board, as do commercial inspections. Some are good...some not so good. Because of the speed with which residential construction happens, the inspections are often cursory with respect to structural items, usually hitting the high spots like wind ties, foundation attachment and general framing to see that headers are there, corners are framed correctly, trusses "look" ok, etc. They pay more attention to plumbing and electrical. They do little or no waterproofing inspection including roofs.

As for real estate transaction inspections, those are driven by either insurance requirements, lender requirements or both. I know of no states in the US having mandatory transaction surveys. Some states require certification of home inspectors. I've heard that there are actually states that will not accept an engineer's inspection report unless he is also certified as a home inspector. Ridiculous. As others have noted, the requirements for home inspection certification are not that difficult. I know one here locally who became certified shortly after retiring from the US Navy as a pilot. My guess is there is little wood framing in an airplane these days.

The "structurally sound" term comes up a lot. The thing we have to guard against is some legislative body defining what "structurally sound" means. We've already had them, in Florida, define "inspection for fatigue" in amusement rides, they've defined "sea walls" but not retaining walls adjacent to any other water body (like every one of them around retention/detention ponds), and various other loosely and poorly defined terms that we then have to spend an inordinate amount of time explaining to non-technical people and others what the real impact is. Waste of time.

In some states, residential structures are not required to be designed by an engineer. Bad move.

 

[JStructsteel]

My inspection of my house focused on the floor being too close to B vent pipe for the exhaust pipe for water heater. keep in mind, it was built this way.


Not a think was mentioned about my retaining wall being out of plumb (failed) by about 6".

House inspections are a joke.

Hire an engineer if you want a thorough inspection of the structure.

 

[Jerehmy]

Ron, in my area it's not required to have a stamp from an architect or engineer to build a residential house. This was surprising to me. Anybody can draw up plans and have them approved for one and two family dwellings.

 

[XR250]

Same with my area as long as it meets prescriptive requiements

 

[boo1]

jrisebo, home inspectors (in Florida) are prohibited from doing any structural inspections (they are not engineers).
Engineers can evaluate (inspect)systems under there area of expertise.

Residential structures engineering requirement have been influenced by builder trade groups to not require engineering.

 

[Jerehmy]

Home inspectors should still be able to recommend hiring a structural engineer to investigate when something in the house looks sketchy.

 

[Guastavino]

Same as in my area.

Meanwhile the Residential code says
"The construction of buildings and structures in accordance with the provisions of this code shall result in a system that provides a complete load path that meets all requirements for the transfer of all loads from their point of origin through the load-resisting elements to the foundation."

Then the next statement (prepare to bury your head in the sand):

"Buildings and structures constructed as prescribed by this code are deemed to comply with the requirements of this section."

In between those two sentences is an assumption that the code provides a complete load path. I don't buy it, but the track record of houses is pretty good. I just feel like the first statement is very misleading. I feel as though the residential code should come clean and say it's a prescriptive method. This half-engineered, half-prescriptive is why I stay away from residential work.

PS - I'm not all negative about the IRC, I don't know what a better solution would be, I just don't think that those statements are accurate together. I think they are misleading at best, and it puts engineers in an awkward spot when reviewing residential structures that clearly don't have a complete load path, but were approved to be built.

 

[ChiefInspectorJeff]

My opinion is that the designer should do the inspections. In lieu of that the insurance companies should have inspectors.
The government inspection process is too corrupt, which is why I left the field after 16 years.
The contractors own the commissioners who control the major who controls the building official.
I can tell you guys that 15 % of inspectors look at all of the structural details and get them enforced.
I failed a contractor for missing 60% of the nails at an osb splice plate designed for uplift and shear.
The boss came out to the job and was on the contractors side. Then the engineer rolled over and said those nails
didn't matter if there were 10 nails above and below the splices IN the side studs. That was not on the plan.
So you see the inspector is attacked on all fronts, and fights a losing battle. A sane person eventually gives up.
Now on to the matter of houses being engineered.In many cases it is not possible to do without steel, which a contractor won't use.
Many Florida counties required engineered wind load design on houses ( which is against State Statute). This puts the engineer in a lose-lose position for it can be proven on many houses that there are no load paths.
I have seen double garage doors with 12" walls between them and called out as shear walls.The above comments are correct in that there are unknown load paths and mechanisms in a house than engineering practice knows, uses or comprehends.
A wall corner functioning as an angle or channel is stronger than a shear wall.





Inspector Jeff

 

[Ron]

Now on to the matter of houses being engineered.In many cases it is not possible to do without steel, which a contractor won't use.
Many Florida counties required engineered wind load design on houses ( which is against State Statute). This puts the engineer in a lose-lose position for it can be proven on many houses that there are no load paths.
I have seen double garage doors with 12" walls between them and called out as shear walls.The above comments are correct in that there are unknown load paths and mechanisms in a house than engineering practice knows, uses or comprehends

??? This makes no sense. Please explain.

 

[ChiefInspectorJeff]

Which part?

Inspector Jeff

 

[Ron]

Now on to the matter of houses being engineered.In many cases it is not possible to do without steel, which a contractor won't use.

What steel are you talking about? If straps, contractors have no issue with installing straps. If tension rods, same thing...however, they don't always install either properly.

Many Florida counties required engineered wind load design on houses ( which is against State Statute). This puts the engineer in a lose-lose position for it can be proven on many houses that there are no load paths.

How is this against state statute? There are load paths on/in every structure. Residential structures are no different.

I have seen double garage doors with 12" walls between them and called out as shear walls.The above comments are correct in that there are unknown load paths and mechanisms in a house than engineering practice knows, uses or comprehends

Competent engineering practice can clearly define the load paths and such is not difficult to comprehend by an experienced engineer.

Please explain your comments so that we might better understand what you mean by them. They are not helpful as stated and seem to have no basis in engineering or fact.

 

[ChiefInspectorJeff]

Quote (ChiefInspectorJeff)
Now on to the matter of houses being engineered.In many cases it is not possible to do without steel, which a contractor won't use.

What steel are you talking about? If straps, contractors have no issue with installing straps. If tension rods, same thing...however, they don't always install either properly.
I am talking about steel columns required for overturning moments under second floor shear walls that occur over garages and are offset 12' from a shear wall.

Quote (ChiefInspectorJeff)
Many Florida counties required engineered wind load design on houses ( which is against State Statute). This puts the engineer in a lose-lose position for it can be proven on many houses that there are no load paths.

How is this against state statute? There are load paths on/in every structure. Residential structures are no different

Florida statute does not require engineering certification on residential and certain commercial jobs.I did not mean engineering is against statutes.
.Try engineering some houses per ASCE and you won't get anymore work.

Quote (ChiefInspectorJeff)
I have seen double garage doors with 12" walls between them and called out as shear walls.The above comments are correct in that there are unknown load paths and mechanisms in a house than engineering practice knows, uses or comprehends
:. Alluding to the fact raised above that there are other untested load paths in houses( electric wiring was mentioned.) I noted that the corner configuration of a wall could be construed to be a channel or angle analogy,imparting more strength to the structure, but is not done according to conventional engineering methods.

Competent engineering practice can clearly define the load paths and such is not difficult to comprehend by an experienced engineer.Many engineers do not know where the load paths are especially with diaphragms and shear walls.They leave out drag struts, chords, etc.

Please explain your comments so that we might better understand what you mean by them. They are not helpful as stated and seem to have no basis in engineering or fact.

The basis in fact is I have done 68,000 inspections and plan review and have seen all of this.
Thus many houses are not engineered to ASCE or codes because to do so would be cost prohibitive as mentioned in above post.They are sealed but do not meet the standards; that is the lose-lose.
One last example.Gable end bracing is attached to the webs of trusses. Was that plate designed to transfer the load to the sheathing? In fact the Fl. engineering board came out with a letter prohibiting the use of x-bracing in 2001.
I have many more examples.
I hope that cleared up the issues regarding structural inspections of residential.


Inspector Jeff

 

[msquared48]

Steel columns at overhanging shear walls? Usually straps or HD'S with 6x6's. Why? Is this a soft story condition?

Mike McCann, PE, SE (WA)

 

[NFExp]

I design houses in Florida on the east coast. I design for all load paths including uplift and lateral from wind. All of the counties we work in have building inspectors to verify all of the structural components. In my opinion the inspectors do a good job since I get calls from contractors all the time for failed inspections. Most of the residential engineers around my area do good job as well. Occasionally I come across a set of really bad structural plans, usually they are from an "out of town" engineer not familiar with the uplift requirements or from an architect who thinks they are an engineer.

 

[Ron]

NFExp....I practice in Florida as well and my experience is similar to yours with regard to the capability of residential design engineers....thus my questions and comments above. I do mostly forensic work which involves a lot of multifamily, condo and single family residences, including evaluations of the structures. The residential structural design is rarely an issue....more often construction.

 

[boo1]

Agree on residential design engineers. But in west FL we have many designs that use deem to comply (SSTD 12) or only have Eng on area that don't meet the SSTD. Our inspectors are not as experienced as NFExp has found. The biggest issues I see are load paths, interior load bearing and shear walls and truss point loads.

 

[medeek]

Aftering working through many residential designs over the past year and half I think that residential designs in this area are thoroughly engineered and inspected. Based on many comments above one would think that residential construction is the bastard child of commercial work but this is not so.

Our local inspector here is very conscientious and careful with both new and remodel work. If the structure is something that does not fit neatly within a prescriptive method that he is comfortable with he turns them over to an engineer and requires a stamped drawing or letter.

With residential work I typically look at the following items for a complete analysis:

Vertical:
Beams
Headers
Posts
Footings
Rafters
Deck Joists
Floor Joists
Uplift

Lateral:

Shearwall (sheathing, chords, connections and holdowns)
Anchor Bolts
Wall Sheathing & nailing
Roof Sheathing & nailing
Stud Wall Check for Biaxial loading

Special situations such as window walls, multi-story, interior shearwalls, girder trusses, highly loaded shearwalls or portal frames require additional analysis and usually another sheet or two of structural drawings.



A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com