irvinehomeshopper
Well-known member
We live in earthquake country and should we buy earthquake insurance.
I have seen the devastations of Semi Valley, Whittier Narrow and Northridge Earthquakes. Prior to these earthquakes constructions were often not monitored and inspected. Code standard were less stringent. Construction defect litigations and lawsuits during the late 80's improve the way builders construct homes.
Regardless of builders reputation the bad craftsmanships are evident in waterproofing, plumbing, finishes and cosmetic appearance. Seismic measure in a home has been a common practice where builders never or rarely cut corner or cheapen up. Shear walls, structural hold down, specified diaphragm, nailing schedules, drag hardware, and wall height to width ratio are built accordingly per architects and engineers design.
The structures that failed during the earthquakes were structure without adequate shear walls or moment frames. Many of there structure were pre 70's and constructed out of multiple materials such as masonry blocks base to wood frame apartment structures. These structures have wide openings without adequate shear walls flanking both ends. The end walls must have a 2 to 1 ratio. If the wall adjacent to the opening on that given story is 10' high the width of the wall must be 5' wide to become an adequate shear wall. This is extremely crucial for the flanking walls at the ends of those 3CWG. Because so much of the house front is relegated to the garage openings very little is left for shear walls. If these flaking walls are narrow and don't meet the 2:1 ratio wood wall then a narrow galvanized metal wall bolted to the foundation can be used for the shear. Older homes did not have these metal walls. The only wood frame house I have seen collapsed or damaged were those that failed around the garage openings and much more susceptible to the 3CWG design.
Wood frame houses is ideal for earthquake zones because the structure is ductile and allowing the entire structure to flex and dissipate energy. The entire wood frame must be bolted to the slab foundation and the entire structure must move with the seismic oscillation. Plaster may crack and window may pop but the structure is relatively well protected from seismic damage. The standard practice in wood framing is typical and therefore is quite consistent through out SoCal and NorCal. Houses don't fall down or collapse during earthquake.
The masonry we see on homes are fake. This is actually better than a true masonry structure from seismic standpoint. The brick and stone are glued to a wood frame exterior wall. The appearance is nice and without the weakness prone to cracking resulting from lateral forces.
After all my gibberish you don't need to buy earthquake insurance if you bought a home built by a builder after 1980's.
You should consider hiring a structural engineer if you have a 3CWG builder home built prior to 1980s to evaluate shear walls and seismic hardwares.
If you have a mid century modern home like the Eichler homes in The Fairhaven tract in Orange the expansive glass openings, the dissimilar materials used in construction, the lack of wood shear walls and deterioration of rigid moment frame then you should also consult a structural engineer for an evaluation.
I have seen the devastations of Semi Valley, Whittier Narrow and Northridge Earthquakes. Prior to these earthquakes constructions were often not monitored and inspected. Code standard were less stringent. Construction defect litigations and lawsuits during the late 80's improve the way builders construct homes.
Regardless of builders reputation the bad craftsmanships are evident in waterproofing, plumbing, finishes and cosmetic appearance. Seismic measure in a home has been a common practice where builders never or rarely cut corner or cheapen up. Shear walls, structural hold down, specified diaphragm, nailing schedules, drag hardware, and wall height to width ratio are built accordingly per architects and engineers design.
The structures that failed during the earthquakes were structure without adequate shear walls or moment frames. Many of there structure were pre 70's and constructed out of multiple materials such as masonry blocks base to wood frame apartment structures. These structures have wide openings without adequate shear walls flanking both ends. The end walls must have a 2 to 1 ratio. If the wall adjacent to the opening on that given story is 10' high the width of the wall must be 5' wide to become an adequate shear wall. This is extremely crucial for the flanking walls at the ends of those 3CWG. Because so much of the house front is relegated to the garage openings very little is left for shear walls. If these flaking walls are narrow and don't meet the 2:1 ratio wood wall then a narrow galvanized metal wall bolted to the foundation can be used for the shear. Older homes did not have these metal walls. The only wood frame house I have seen collapsed or damaged were those that failed around the garage openings and much more susceptible to the 3CWG design.
Wood frame houses is ideal for earthquake zones because the structure is ductile and allowing the entire structure to flex and dissipate energy. The entire wood frame must be bolted to the slab foundation and the entire structure must move with the seismic oscillation. Plaster may crack and window may pop but the structure is relatively well protected from seismic damage. The standard practice in wood framing is typical and therefore is quite consistent through out SoCal and NorCal. Houses don't fall down or collapse during earthquake.
The masonry we see on homes are fake. This is actually better than a true masonry structure from seismic standpoint. The brick and stone are glued to a wood frame exterior wall. The appearance is nice and without the weakness prone to cracking resulting from lateral forces.
After all my gibberish you don't need to buy earthquake insurance if you bought a home built by a builder after 1980's.
You should consider hiring a structural engineer if you have a 3CWG builder home built prior to 1980s to evaluate shear walls and seismic hardwares.
If you have a mid century modern home like the Eichler homes in The Fairhaven tract in Orange the expansive glass openings, the dissimilar materials used in construction, the lack of wood shear walls and deterioration of rigid moment frame then you should also consult a structural engineer for an evaluation.