Building a house in an earthquake zone, such as the Wasatch Front, requires extra effort. But it is well worth it. Structural engineering provides the greatest assurance that lives will be protected when a big earthquake hits. And it is not a question of if an earthquake hits, it’s a question of when.
You may ask, "If plans are engineered, doesn’t the house get engineered? Doesn’t the inspector make sure that the house is built the way it should be?"
Subcontractors should know and implement engineering designs. And city/county building inspectors should inspect and insure that they do. But engineering codes have been changing every year and subcontractors do not always know or agree with the latest engineering requirements.
Building inspectors are more likely to be aware of current engineering codes. But they can’t always be at the job site and don’t have time to inspect everything. This is the responsibility of the general contractor.
A general contractor must understand all the plan’s engineering specifications and he must ensure their implementation. Discovering and retrofitting inadequate steel or concrete is not feasible once the concrete has been poured!
Structural engineering components are installed in the house mainly through three means: Footings, foundation and framing. The following are a few decisive questions regarding structural engineering:
Has the soil been tested by an expert? Have the right information been conveyed to the structural engineer for adequate design?
Is the engineer well-known for his thorough and practical design or is he a "rubber-stamper" willing to emboss his seal on any plan for a fee?
Will the engineer be available for consultation should a question or problem develop?
Are the footings on native soil or properly compacted fill?
What is the strength of the concrete considering any extra water that has been added?
Is the width correct?
Is the depth sufficient everywhere? If there are places where the depth is not adequate, who is on the job site to fix it?
Are spot footings the proper size and in the proper location?
Are the garage openings tied together?
Is (are) the steel the right size(s)? Is it wired together correctly and lapped properly?
Is the steel correctly placed to obtain optimum strength?
Is the horizontal and vertical steel in the right place and in the right quantity? What about over windows and doors?
Are the top bars the proper distance from the top of the foundation? Is the bottom bar the required interval from the footing?
Are the anchor bolts the right size and in the correct place? What size would the engineer want to use on his own home?
Are the holdowns the right size and in the right place? How do 2 x 4 and 2 x 6 walls and masonry/stone veneers affect bolt and holdown placement? Holdown placement is very important and must be checked!
Is the required grade of lumber being used?
Do the anchor bolts have the specified washers?
Are the right size and number of nails being used in shear walls, in stud framing, in hangers, and especially in holdowns and straps?
Are shear walls flush nailed?
How would an engineer nail sheathing on his own home?
Is all the wall and roof sheathing gapped according to manufacturer’s specifications?
Are the studs being spaced as required?
Are the floor joists, beams and posts the correct size and in the proper location?
Do the headers have the correct number of trimmers supporting them and does the load adequately transfer through the floor to the footings?
Are the 2nd story and glu-lam straps the appropriate size and installed as required?
Are the overbuild areas sheathed correctly? Are overbuild rafters supported as required?
Are the trusses nailed and braced according to the truss specifications?
Do roof girder trusses have the required number of trimmers?
Have any trusses been damaged or broken? If so, where does one get the required truss fix? Who will fix them?
Are all hangers correct?
Where can TJIs and top plates be cut? Where can they not?
12 Common Framing Mistakes
The structural engineering and truss layout don’t integrate which puts the girders and point loads in the wrong places.
Non-continuous load path.
Sinkers are used instead of common nails. Sinkers are shorter, narrower and coated for quick application. Engineering specifications are based upon the size and strength of common nails.
Rafters are undercut.
Overbuild areas are not sheathed or supported correctly.
Shear walls are not flush nailed.
Sheathing in walls and roof is not gapped as required.
TJIs are cut inappropriately.
Hangers are the wrong size, missing and are nailed incorrectly.
Trusses are not nailed or braced properly.
Damaged trusses are not fixed.
Staples are applied perpendicular instead of parallel to studs.