EARTHQUAKE BRACE AND BOLT PROGRAM COST

    HOW TO MAKE THE MOST OF THE EARTHQUAKE BRACE AND BOLT PROGRAM

Earthquake Brace And Bolt Program (EBB) seismic retrofit contractors must use Standard Plan A or FEMA P-1100/ICC 1300 to get your $3,000grant .  For low income it can be as high as $10,000.  The author was involved with both committees that wrote these Earthquake Brace And Bolt guidelines. Here I am offering a cost comparison between these retrofit guidelines.   The pricing per piece of hardware and price per linear foot of plywood is based on Bay Area Retrofit’s current pricing.

Standard Plan A was created by a volunteer ad hoc group of engineers, building officials, and a contractor (yours truly) at no expense to the taxpayer.  Standard Plan A is based on a study done by the National Science Foundation which predicted damage based on on actual statistics from both the Northridge and Loma Prieta Earthquakes as found on page 4 of this study. 

EARTHQUAKE BRACE AND BOLT PROGRAM STATISTICS

                                    EARTHQUAKE BRACE AND BOLT PROGRAM STATISTICS

FEMA P-1100 was created by a group of Ph.D. wood scientist and engineers for a cost of $22,400,000 in tax payer money using government grants from FEMA thru the Applied Technology Council which survives on government grants.  No contractors who actually do the work were included. Rather than empirical evidence, it is based on computer modelling and engineering theory as well as various lab tests and reports.  A list of these lab tests and reports can be seen here.  

T

TOTAL COST OF FEMA P-1100

                                            TOTAL COST OF FEMA P-1100

Links to these studies can be seen here.  

Below Is A FEMA P-1100 vs. Standard Plan A Comparison For a 1350 Square Foot 1-Story Light Construction House

1350 Square Foot Light Construction FEMA P-1100 Design Compared To Standard Plan A

$16,080.00

1350 Square Foot Light Construction Standard Plan A Design Compared To FEMA P-1100

$5,622.00

Balanced Engineering  

The earthquake resistance of each component, i.e., the bolts, plywood, and L90s, should be more or less equal to create a balanced and money saving retrofit. The thinking behind this is that a retrofit is only as strong as its weakest connection. The plywood, bolts, and L90s work as a system. If one component fails the entire system fails. For example, in the FEMA P-1100 retrofit above the L90s can resist 18,000 lbs  of force on each wall line, the plywood 9,120 Lbs, and the bolts 23,125 lbs.  The retrofit will fail as soon as it must resist 9,120 lbs. of force provided by the plywood; anything over that in the L90s and plywood  earthquake resistance is redundant and a waste of money.  In this case  all 4 wall lines total 56,020 lbs. of excess bolts ($2,875.00) and 35,120 lbs. of excess L90s ($1,480.00).  This exceed hardware translates into $4,355.00 of excess cost.   Here is a 3:40 video that explains how balanced retrofits work.

A 1350 Square Foot 1-Story Medium Construction Comparison

1350 Square Foot Medium Construction FEMA P-1100 Design Compared To Standard Plan A

$17,784.00

 

1350 Square Foot Medium Construction Standard Plan A Design Compared To FEMA P-1100

$6,644.00

These two figures compare a FEMA P-1100/ICC 1300 retrofit (on the left) with a Standard Plan A retrofit (on the right) for a medium construction 1,350 square foot house. A Standard Plan A retrofit will cost $6,644, compared to $17,784 for a FEMA P-1100/ICC 1300 retrofit. Notice how grossly out of balance the FEMA P-1100 retrofit is. The 21,000 lbs. of bolt capacity in p-1100 exceeds the 11,760 lb. plywood capacity by 9,240 lbs on each wall line for a total of $4,320.00 excess cost when the excess on all four wall lines are added together. We also find 15,065 lbs. of excess  L90 capacity on each wall line (60.260 lbs. when all four wall lines are added together) for a total of 65 excess L90s  ($3,198). These excess bolts and L90s cause this P-1100 retrofit to be far more expensive than it needs to be.

On the other hand, the Standard Plan A retrofit is balanced with 6,600 lbs. of plywood, 6,000 lbs. worth or bolts, and 6,475 lbs. of L90s on each side. This balanced Standard Plan A retrofit costs considerably less because it is balanced.

A 1350 Square Foot 1-Story Heavy Construction Comparison.

1350 Square Foot Heavy Construction FEMA P-1100 Design Compared To Standard Plan A

$19,592.00

1350 Square Foot Heavy Construction Standard Plan A Design Compared To FEMA P-1100

$7,342.00

Again, notice how grossly out of balance the FEMA P-1100 retrofit is.

Comparing 2-story Retrofits

FEMA P-1100/ICC 1300 two story retrofits use the same EARTHQUAKE RETROFIT SCHEDULE as 1-story houses. The only difference is that these retrofits often use holdowns, (called tie-downs in the table), which resist overturning forces.

A 3150 Square Foot 2-Story Light Construction Comparison

Applying the same thinking process we used in evaluating 1-story houses shown below, we see the P-1100/ICC 1300 retrofit on the left will cost $49,384, compared to a $9,158 Standard Plan A retrofit shown on the right. 

Again, notice how grossly out of balance the FEMA P-1100/ICC 1300 retrofit is where the capacity of the plywood is 18,240 lbs., the bolts almost twice that amount at 18,240 lbs., and the L90s almost three times that amount at 44,000 lbs. All of this excess increases costs immeasurably. 

Compare this to the almost perfectly balanced Standard Plan A retrofit with 8,800 lbs. of plywood, 9,000 lbs. worth or bolts, and 9,250 lbs. worth of L90s on each wall line.

Notice how the available foundation on the P-1100 retrofit is less than the linear footage of plywood required by FEMA P-1100. In my experience with designing seismic retrofits for two story houses, which are invariably rectangular, I cannot think of a single instance where P-1100 will work on a two story house.   This will be the case even if the house is a perfect square. 

SAMPLE TWO STORY FEMA P-1100 RETROFIT 3150 SQUARE FOOT LIGHT CONSTRUCTION

$49,384.00

COMPARISON SAMPLE TWO STORY STANDARD PLAN A RETROFIT 3150 SQUARE FOOT LIGHT CONSTRUCTION AND FEMA P-1100

$9,158.00

 

 

3150 Square Foot 2-Story Medium Construction Comparison

Assuming 2-story houses where FEMA P-1100 will work actually exist, when we apply the same thinking process used for 1-story houses to this house we discover that this FEMA P-1100/CC 1300 retrofit will cost $47,284 compared to a $22,530 Standard Plan A retrofit. The same problem with balance applies here. Notice how the Standard Plan A retrofit is almost perfectly balanced.

SAMPLE TWO STORY FEMA P-1100 RETROFIT 3150 SQUARE FOOT MEDIUM CONSTRUCTION

$47,284.00

COMPARISON SAMPLE TWO STORY STANDARD PLAN A RETROFIT 3150 SQUARE FOOT MEDIUM CONSTRUCTION AND FEMA P-1100

$22,530.00

3150 Square Foot 2-Story Heavy Construction Comparison

When we apply the same thinking process to this house we discover that the FEMA P-1100/ICC 1300 retrofit will cost $55,276 compared to a $24,392 Standard Plan A retrofit. The same problem with balance applies here.

SAMPLE TWO STORY FEMA P-1100 RETROFIT 3150 SQUARE FOOT HEAVY CONSTRUCTION

$55,276.00

COMPARISON SAMPLE TWO STORY STANDARD PLAN A RETROFIT 3150 SQUARE FOOT HEAVY CONSTRUCTION AND FEMA P-1100

$15,840.00

No Cripple Wall Retrofits

Here we compare a 2-story 3,150 square foot medium construction P-1100 retrofit of a house without cripple walls. In this retrofit we are using the Type B Connector (the brand name is the Simpson Strongtie FRFP) from the EARTHQUAKE RETROFIT SCHEDULE which is  FEMA P-1100/ICC 1300 approach and compare it to a 3,150 square foot 2-story Standard Plan A retrofit no cripple wall retrofit (on the right) which uses the Simpson StrongTie URFP. The FEMA P-1100/ICC 1300 retrofit will cost $42,793, compared to a $6,438 Standard Plan A retrofit.

SIMPSON STRONGTIE FRFP TWO STORY P-1100 RETROFIT 3150 SQUARE FOOT MEDIUM CONSTRUCTION

$43,793.00

SIMPSON STRONGTIE URFP TWO STORY SIMPSON P-1100 RETROFIT 3150 SQUARE FOOT MEDIUM CONSTRUCTION

$6,438.00

In this last part of our study we look at what happens when a FEMA P-1100/ICC 1300 construction detail seen on the lower right is applied to a medium construction 1,350 square foot single story house. A construction detail is a drawing that shows a contractor how to build something.

The dark and light blue lines in the detail are 4 foot long shims called “runners”. The red lines are Type B Connectors (Simpson FRFPs). This is another case where the linear footage of foundation is not long enough for the length of the plywood required by the EARTHQUAKE RETROFIT SCHEDULE. The detail has many other problems, including a building code violation. This is fully described in this video.

ABSURD CONSEQUENCE OF FEMA P-1100 RETROFIT USING ITS CONSTRUCTION DETAIL

FEMA P-1100 CONSTRUCTION DETAIL USED IN DRAWING TO THE LEFT.

  

Conclusion

The original FEMA P-1100 did not have any contractors on the committee which is reflected in its impracticality and high cost.  It is analogous to a group of aeronautical engineers writing a manual on bicycle writing when none of them had ever ridden a bicycle.  This lack of practical considerations had the following consequences. 

  • The average average homeowner will not be able to afford FEMA P-1100 retrofits. 
  • Their high cost is driven  by imbalanced engineering. 
  • The retrofits are designed to resist improbably high lateral forces which increase cost. .
  • The anticipation of high lateral forces was based on computer modelling rather than the empirical evidence used by Standard Plan A increases cost.  
  • Lower lateral forces based on  empirical evidence is not only more accurate, but the retrofits need to resist these lower forces are far cheaper.
  • These high forces make FEMA P-1100/ICC 1300 impossible to use on two story homes. 
  • Small changes could be made to its requirements such as requiring Structural 1 sheathing rather allowing rated sheathing.  This alone would result in a 13% savings.  

Solutions For The Earthquake Brace And Program

The  most sensible thing to do would be to revise the tables and include contractors who understand cost and the needs  of the average homeowner.   In addition, Standard Plan A, which was revised in 2008 such that its retrofits are half as strong as originally intended. It should be revised again  and newer and stronger types of hardware should be used.  My recommendations for revisions can be seen here.  This will not only reduce cost but will provide 2 alternatives for seismic retrofit contractors to use.