Can your contractor answer these questions?
Educating yourself is very important because there is no retrofit building code or special licensing for retrofit contractors.
See "False Security" for more.
Approximately 70% of the retrofits we perform involve repairs of jobs done by well-meaning contractors who did not understand the principles and practice of effective seismic retrofitting. An engineer is not necessary so long as the contractor understands the engineering principles behind effective retrofitting.
When interviewing contractors only a few questions need be asked to see if they areknowledgeable:
Question 1:)
Does he know what the base shear formula is and how it would apply to the construction of your house. (For more info see Retrofit Design)
Question 2:
Does the contractor have a wood frame structural engineer he consults, and will that engineer verify that the contractor understands wood frame seismic retrofit engineering principles? If the contractor cannot produce a competent wood frame engineer who can attest to the contractor's knowledge it means he has no understanding of the engineering. This is essential in any retrofit.
Question 3:
Has he read Thor Matteson's 110 page book on shear wall construction. (See www.Shearwalls.com). This is the bible of shear wall construction and any retroft contractor should be very familiar with it.
Question 4:
Does he know which organization is responsible for shear walls tests and what document contains the results of the tests?
Answer: The American Plywood Association and APA Research Report 15.4
Question 5:
Does he know which chapter in the International Existing Building Code applies to wood frame retrofitting and can he name it as Chapter Appendix Chapter 3?
Question 6:
Does he know in new construction a shear wall must be at least 4 feet wide if it is 8 feet tall?
Question 7:
A contractor or engineer must determine the earthquake-resisting value of existing materials on old houses such as horizontal siding, old foundations, plaster, etc. Does he know this information is found in Table A-1-D of the International Existing Building Code?
If a contractor can answer at least 2 of these questions accurately he is worth considering.
Question 8:
Does he know that a structural engineer
who has a "S.E." has advanced training, experience and knowledge over and above that of a civil engineer who has a "C.E." after his name? Does he use a structural engineer?
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