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Standard Plan A

 Standard Plan A:  Retrofit Guidelines for the Bay Area

 Critiqued by a Member of the Standard Plan A Development Committee    

This critique of Standard Plan A ( you can download from here everything you need to use this standard) was written by Howard Cook, a member of the Tri-Chapter International Code Council committee which developed Standard Plan A.

This standard was supposed to replace, reduce cost,  and otherwise improve Appendix Chapter A3 of the California Existing Building Code.

The Engineering Background of Standard Plan A

Being a member of the Standard Plan A committee,  I was given a copy of these calculations.  We use these calculations to design every retrofit we perform.

Background and History of Standard Plan A

As a consequence of the Northridge earthquake, the California Earthquake Authority (CEA) sponsored an $8 million residential retrofit program that worked like this: Homeowners would call an 800 number and schedule a structural engineering firm to come out and evaluate their homes. The CEA would pay the firm $800 for this service. While the engineers were on site, they would offer to draw up a set of retrofit plans for the people’s homes for a cost of between four and six thousand dollars.  Bay Area Retrofit was an approved contractor and after noticing some problems with the recommendations of these engineers they informed Mr. Jim Russel.

Mr. Jim Russell, who was a founding author of Appendix Chapter A3, believed that the engineering basis and the construction details used in Appendix Chapter A3 were in many cases difficult to apply.  He was a specialist in wood frame retrofit engineering and former chair of the City of Los Angeles Task Force that evaluated residential wood frame earthquake damage after the Northridge earthquake.  This is the same committee that created the Los Angels retrofit standards.

Consequently he contacted all of the Bay Area building departments to see if they would be willing to meet and develop a set of retrofit guidelines that would be an improvement to the standard he helped write decades prior. Out of this the Tri-Chapter ICC (International Code Council) Wood Frame Retrofit Committee was formed.   Unfortunately, Mr. Russell could only attend three or four meetings before he had to stop due to ill  health.

 

This Information Belew is from an Analysis Howard Cook did while on the Berkeley Disaster Commission

  Plan Set A—Full Text and Commentary

The following pages are my appraisal of ICC Plan Set A and its applicability to Berkeley homes.

  • The Plan Set is shown here in quotes, as published by the ICC, in plain (not bold) font.
  • My commentary is embedded within the Plan Set document in bold italics text.
  • A summary of my recommendations follows the Plan Set.

“GENERAL INSTRUCTIONS:

READ FIRST

“To determine if your home qualifies please answer the following questions.   If you answer yes to all of the following questions your home qualifies to use this standard.”

The following is the first page of the Plan Set.  The answers to these questions let the homeowner know if he or she will be able to use the Plan Set or will have to call an engineer or architect instead.  This document refers to “YOUR HOME” and was meant for homeowners with little or no construction experience who were planning to do this work themselves.

“IF YOU ANSWER YES TO EACH OF THESE QUESTIONS, PROCEED TO APPLICANT INSTRUCTIONS.

“DOES THIS PLAN SET APPLY TO YOUR HOME?

“1. Is your home a one or two family residential structure?

“2. Is your home two stories or less?

“3.  Is your home wood-framed construction?

“4. Does the building have a continuous perimeter concrete foundation (ignoring the intermediate area surrounding the fireplace)?”

Houses with front porches very rarely have a continuous foundation along the front of the house. Usually there are only posts holding up the back of the porch or stairs.  The foundation often follows the front of the porch rather than the front of the house.  The requirement that a house have a continuous perimeter foundation disqualifies about 75% of the Berkeley homes I work on.

“5.  Does your house have a crawl space?

“6. Are all the cripple walls less than 4 feet in height? (See detail in lower left corner of plan set for an example of a cripple wall.)”

Many homes in Berkeley are on hillsides. In these homes, some of the cripple walls are almost invariably over 4 feet tall.  I find cripple walls over 4 feet tall in hillside homes at least 95% of the time.

Many houses in the flats, including the house I live in, are raised up off the foundation more than 4 feet.  This was simply a common style of construction before the 1940’s.  Many homes in the flats also have parking underneath.  The Plan Set will not apply to these homes, so these homeowners will be forced to hire an engineer or architect. Addressing the retrofit of cripple walls over 4 feet tall is not difficult and could easily have been part of a prescriptive retrofit code.

“7. If your home has brick or stone veneer along the exterior walls (excluding any chimneys), is the maximum height of the veneer maximum 4 feet above the foundation? (If your home does not have any brick, or stone veneer, you should answer this question as a YES.)

“8. If the roofing of your home is clay tile, are the tiles installed without the use of mortar along the tile edges? (If your home’s roofing is a material other than clay tile you should answer this question as a YES.)

“IF YOU ANSWER NO TO ANY OF THESE QUESTIONS CONTACT YOUR LOCAL BUILDING DEPARTMENT FOR ASSISTANCE.”

As the proposed changes in the ordinance now stand, building officials will have no choice but to tell most people that they must hire an engineer or architect.

“PURPOSE

“1. These plans set standards for strengthening may be approved by the building official without requiring additional plans or calculations.  They provide a low-cost method to help improve your home’s chances of surviving an earthquake using a method that is quick, easy and inexpensive.”

This is not true.  Even if the Plan Set applied to a Bay Area house, its use would be expensive. At my present pricing and using my own prescriptive standard developed over many years, an average single-story stucco home less than 1200 square feet costs $5,540 to retrofit. Using the Plan Set, for a single-story stucco home less than 1200 square feet I would have to charge $9,280.  A two-story stucco home would cost $6,480 to retrofit using my standards and $14,000 using the Plan Set.  As will be shown later from an engineering point of view, there is a lot of redundancy in the Plan Set approach which unnecessarily drives up the cost of a retrofit.  It is meant for a homeowner who is doing the work himself and is not concerned about taking a lot of time.

Summary of Recommendations

The Standard Plan A retrofit Building Code could have included retrofit requirements for most of the Berkeley housing stock, thus

  • saving Berkeley homeowners thousands of dollars
  • giving engineers and architects the code guidelines they need for designing effective retrofits
  • relieving the Building Department of the extra work involved in determining the large number of cases in which conditions exist outside the scope of Plan Set A.

 PERMIT & INSPECTION REQUIREMENTS

SUBMIT A PERMIT APPLICATION AND 2 COMPLETED PLAN SETS TO THE BUILDING DEPT. FOR REVIEW (PHOTOGRAPHS OF THE MUD SILL, CRIPPLE WALL, AND FLOOR FRAMING CONDITIONS MAY ASSIST THE REVIEW PROCESS).

PRIOR TO COMMENCEMENT OF WORK THE PERMIT HOLDER MAY BE REQUIRED TO SCHEDULE A PRE-CONSTRUCTION INSPECTION WITH THE BUILDING DEPARTMENT TO VERIFY THAT FIELD CONDITIONS ARE CONSISTENT WITH THE INFORMATION PROVIDED ON THE APPROVED PLAN.

INSPECTIONS BY THE BUILDING DEPARTMENT ARE REQUIRED FOR:

  • FOUNDATION BOLT/ANCHOR PLATE INSTALLATION,
  • INSTALLATION OF BLOCKING,
  • PLYWOOD PANEL INSTALLATION ON CRIPPLE WALL,
  • METAL HARDWARE INSTALLATION, AND
  • FINAL INSPECTION.

NO WORK REQUIRING INSPECTION SHALL BE COVERED UNTIL IT HAS BEEN INSPECTED AND APPROVED BY THE BUILDING DEPARTMENT.

PRIOR TO FINAL INSPECTION, SMOKE DETECTORS SHALL BE INSTALLED IN THE ATTACHED DWELLING(S) IN ACCORDANCE WITH BUILDING CODE REQUIREMENTS.

SAMPLE PLAN
Retrofit Guidelines Foundation Plan
SAMPLE FOUNDATION PLAN & PLYWOOD PANEL LAYOUT FOR A 1200 SF 1-STORY HOUSE OF LIGHT CONSTRUCTION

This Sample Plan does not look like the Berkeley houses I work on.  As stated earlier, many Berkeley homes do not have a continuous foundation along the front of the house.  It is also true that many Berkeley homes have additions in the back.  Additions require special retrofit techniques to prevent them from becoming detached from the main house.  The Plan Set does not address the retrofit of additions.
Cripple Wall Bracing for Retrofit Guidelines

NOTES.

1. THIS DETAIL SHOWS A SAMPLE CRIPPLE WALL WHICH HAS UNDERGONE A TYPICAL SEISMIC STRENGTHENING

2. THIS DETAIL IS NOT INTENDED TO SUPERSEDE REQUIREMENTS CONTAINED IN THE SPECIFIC INSTALLATION DETAILS ON SHEET 2 OR THE PLAN SET BOOKLET.

Note the “NEW BLOCKING” that the plywood is nailed to.  The American Plywood Association, which is the testing agency that tests and develops plywood shear walls for all model building codes used in the United States, has determined that using nailed blocking is the least desirable way to attach a shear wall to the bolted mudsill.  The reason this method is problematic is twofold:

The blocks tend to split and shear walls built with wood blocking are not very strong. The engineer who determined the strength of the retrofit shear walls for the ICC Plan Set determined them to have a value of 380 pounds of earthquake resistance per each linear foot of plywood using 8 penny common nails spaced 4 inches apart.  The nails should not be spaced any closer together because of concerns that the blocks will split.  The American Plywood Association has never tested shear walls nailed to blocks.  On the other hand, the American Plywood Association did test shear walls where the mudsill and all other framing member were 2 by 4’s. This is referenced on page 5 of American Plywood Association Research Report number 154 entitled Wood Structural Panel Shear Walls by John Tissell, P.E.  His tests determined that shear walls using 15/32 structural one plywood nailed 2 inches apart on the edges have a tested value of 730 pounds per linear foot. Splitting was not a concern here because full length framing members do not split easily

The results of the APA tests can be found in Table 23-II-I-1 ALLOWABLE SHEAR FORCES FOR WOOD STRUCTURAL PANEL SHEAR WALLS found on page 2-288 of the 1997 Uniform Building Code.  These tested values can only be achieved by using the “Flush-Cut” method of building retrofit shear walls. This method changes the mudsill into a 2 by 4 so that all framing member are now 2 by 4’s, exactly as tested by the APA.  This shear wall configuration can resist almost twice as much force as a shear wall using blocks. If higher capacity flush cut, reverse blocking, or stapled blocking methods are used, only half as much linear footage of plywood may be required along each wall line.  The alone will reduce the retrofit cost of the single story stucco house from $9,280 to $6,680.  These higher capacity walls can only work if other parts of the retrofit are designed and detailed very carefully.

Retrofit Guidelinies, Plywood and Linear footage of shear walls

The table on the previous page is a condensation of the engineering calculations that form the basis of the Plan Set.  The table is based upon shear walls having strength of 380 pounds per linear foot, 820 pounds for a ½ inch bolt, and 1170 pounds per a 5/8-inch bolt.  Please see pages 1 and 2 in APPENDIX B in the appendix.

In the left hand column table it requires that additional bolts be placed at non plywood-braced locations. However, earthquake forces are transferred only to those bolts that are attached to a plywood panel.

Before continuing with comments on the table, please read the following answers to questions that were posed to a number of experienced wood frame structural engineers in a document called Retrofit Code Questionnaire.  This is a questionnaire that I sent to a number of engineers as part of the ICC committee.   The position of the letters represents how the engineers answered the questions.  Please see Appendix C.

“3)- Some engineers believe that all the earthquake forces go to the stiffest element, (in this case the shear panel is the stiffest element), and therefore only the bolts that are attached to the shear panel absorb any force.

 The questions are:  Is it true that all the earthquake force goes to the stiffest element and therefore only to the shear panels?  Or, as Nels Roselund puts it: most of the force goes to the stiffest element; slightly less force goes to a slightly less stiff element.

 (These are the initials of the participating engineers) Ke, L, R, S, T    Yes  __B__Indeterminate

 Relevance to Code:  This is extremely relevant, as it means bolting outside of shear panel locations is probably not necessary and also very expensive.   It appears that installing bolts that are not connected to the shear panels, while adding greatly to the cost of a retrofit, offer little or no protection. 

 Question:  If the retrofit design makes sure that the shear capacity of the bolts attaching the shear panel to the foundation matches the capacity of the shear panel itself, is it still important to put bolts between 8 and 12 inches of the mudsill ends as currently required by the UBC and UCBC?

____Yes   Ke, L, R, S, T, B    No

 Roselund, Tipping, and Kennedy-Bolts at the end of mudsills are not necessary so long as each section of mudsill attached to a shear wall has at least two bolts to prevent out of plane rotation

 Relevance to code:  This information is relevant because it means it is not necessary to maintain UBC bolt end distances when doing retrofit work.   This is important because it is often not possible to maintain these distances because of lack of access.  The critical thing appears to be in maintaining equality in strength capacities between the shear walling and the bolts attached to the shear wall.   

 3a) If it is true that most of the force goes to the stiffest element; slightly less force goes to a slightly less stiff element, how much earthquake load is transferred to the part of the cripple wall that has no shear walling?

 Loar, -Only a negligible amount of earthquake force transfers to the unbraced sections of cripplewall.

 Sonntag, Tipping, Kennedy,- No shear forces will  travel to the sections of cripple wall that have no plywood shear-walling. It is therefore not necessary to install bolts along the mudsill at non-shear wall locations.  Whatever is currently holding the mudsill in place at non-shear wall locations is probably enough. 

 Schmid-Indeterminate, but assume the stucco on exterior sheathing offers some resistance. 

 Roselund, Very little shear forces will  travel to the sections of cripple wall that have no plywood shear-walling, depending on the existing wall sheathing – stucco in good condition will carry a lot of shear, but once the nails have corroded, it’s not worth much.

 In a retrofit, is it necessary to bolt the sections of wall currently braced with horizontal siding or stucco that have no additional plywood shear walling?

 _B__ Yes          Ke, L, R, S, T    No

 Relevance to code:  This information is relevant because all existing retrofit building codes (UCBC, GREB, San Leandro, and Los Angeles) now recommend installing bolts 6 feet on center regardless of the placement of the shear walls. This results in the installation of many redundant bolts and unnecessarily increases the cost of the retrofit. “

A lot of Berkeley homes are rectangular and the front and back are about 24 feet wide.  The foundations are 24 feet long unless interrupted by a porch. I find porches on probably 95% of the Berkeley houses I work on.  In addition, there are often obstructions such as pipes and gas meters that make installation of plywood shear walls impossible.  The Plan Set Table (see the top red arrow) requires 20 linear feet of shear wall on a one-story stucco house that is 1200 square feet or less. Because of the porch and other obstructions, it is rarely possible to find 20 linear feet of usable foundation upon which to build plywood shear walls on the front and back of the house.  For a 2400 square foot house (see the lower red arrow,) 1200 square feet above and 1200 square feet below, the Plan Set dictates that 29’4″ of shear wall be installed on a foundation that is often only 24 feet long at the front and back of the house! Most two-story homes in Berkeley are on small lots and are narrower than 24 feet. It is doubtful that many two story Berkeley homes will quality for use of the Plan Set.

The problem with insufficient foundation could be eliminated if the low capacity shear walls recommended by the Plan Set were substituted with high capacity shear walls.  This is because with high capacity shear walls, the required linear footage of shear wall shown in the table could be cut in half. This is only possible if the nailed blocking method of building retrofit shear walls is substituted with the higher capacity flush cut, reverse block, and stapled block method.  It must be noted that when high capacity shear walls are used other parts of the retrofit must be carefully detailed and designed.

The table below is part of the Plan Set and rates the strengths of the L70’s, L90’s and bolt hardware used in the Plan Set.  The connectors are rated in pounds and specify how many pounds of earthquake force each connector can resist.
Table: Retrofit Guidelines Connector Capacity

The L70, also known as the Simpson L70 because it is made by the Simpson Strong-Tie company, is rated to resist 460 pounds of earthquake force when used to connect Douglas fir to Douglas fir, such as in the floor framing to cripple wall top plate connection. When this connector is used to connect Douglas fir to redwood, such as when connecting the floor framing directly to the mudsill, the strength of the L70 connector is reduced to 395 pounds.  The L90, also made by Simpson Strong-Tie, is rated to resist the 600 pounds shown in the table above for Douglas fir to Douglas fir connections. When the L90 is used to connect Douglas fir to redwood the strength of the connector is 520 pounds.  Each connector should have two listed values depending on the species of wood being connected.  Please see APPENDIX D from Simpson Strong Tie.

Interestingly, the values used by the ICC found on page nine of Substantiating Data For Cripple Wall and Sill Bolting by Mr. Jim Russell, P.E., which were used to justify the amounts of plywood and hardware used in the STANDARD PLAN SET A SCHEDULE are different from the values listed in the chart above, and somewhat different from the values given by Simpson manufacturing.  See page 7 of APPENDIX B.  The values used in Mr. Russell’s document are 450 pounds for the L70 and 585 pounds for the L90 and no special consideration is given to redwood. I doubt such a small strength discrepancy in the Douglas fir to Douglas fir connections provided by the L70 and L90 will have any effect on the STANDARD PLAN SET A SCHEDULE.  I believe it will make a big difference in the PLAN SET SCHEDULE where the Douglas fir to redwood connections are concerned.

As part of the efforts of the ICC committee, I contacted the American Wood Council, the organization that determines and publishes the strength of bolted wood to concrete connections.  It is their opinion that the ½ inch bolt has a value of 992 pounds in new Douglas Fir blocking and 1081 pounds in two inch thick old growth redwood mudsills. This contradicts the 820 pounds found in the Plan Set.  It is also their opinion that 5/8 bolts have a value of 1424 pounds when installed in new 2 by 4 blocks and 1499 pounds when installed in 2-inch thick old growth redwood.  Calculated bolt values using the building code are also much higher than the values given by Mr. Russell. This is significant because the number of bolts listed in the Plan Set Schedule could be reduced by almost 25% if these higher values were used. This would significantly reduce the cost of retrofits to Berkeley homeowners. Please see APPENDIX E.

There is a formula for determining the ability of a bolt to resist earthquake forces and difference in bolt values between the American Wood Council and the ICC can be traced to this multiplier. The ICC used a 1.3 multiplier instead of the 1.6 multiplier allowed by the Uniform Building Code.  In the footnote to TABLE 2-3.2 on page 2-292 of Volume 2 of the Uniform Building Code it says, “1.6 may be used for nailed and bolted connections exhibiting Mode III or Mode IV behavior.” I cannot explain it here, but any engineer will tell you that ½ or 5/8 bolts in 2 inch thick mudsills required to resist earthquake forces exhibit Mode III behavior; so the use of 1.6 multiplier appears to be fully justified.  1.6 will also be the multiplier used in the soon to be adopted International Building Code.  I objected to the use of 1.3 to the committee but was told “because the L70’s and L90’s only allow 1.3, we are also going to use it on the bolts” and was overruled.  Please see APPENDIX F.

The value listed in the table for the l70 and L90 is also inaccurate.  Please see APPENDIX D. The reason the ICC ignored the redwood and Douglas fir differential can be found on page one of Substantiating Data For Cripple Wall and Sill Bolting by Mr. Jim Russell, P.E. where it states: “For determining bolt capacities, foundation sill plates are considered to be tight grained redwood. Based on observations, and some limited testing, the dowel bearing strength of this species is considered to be equivalent to Douglas fir having a specific gravity of 0.50.”

“Observations” refers to a day when I took a piece of flush-cut redwood mudsill to the ICC meeting. To my knowledge no actual testing has been done. I contacted Mr. Charlie Jordain, the technical advisor at the California Redwood Association, 415-382-0662, about this and he too knows of no testing.

I contacted Mr. Russell about this.  He told me that he believed I told him the APA had done some tests.  I have since told him that they had not done any testing and that I had simply sent a section of flush cut Mudsill to Mr. Skaggs.

The Plan Set Schedule should be probably be reworked based on accurate L70 and L90 values in Redwood, high capacity shear wall values, and accurate bolt values.  This would result in a more usable document as well one that makes retrofitting more cost-effective for homeowners.

Drawing: Retroift Guidelines Hardware

The “Floor Joists Parallel to Foundation” detail shows what it normally looks like at the front and back of a house.  The arrows mark where L90 or L70s are to be installed a minimum of 16” o.c. (o.c means “on center” or apart.)  On a wooden single story house the Plan Set Table requires 14’-8” of plywood shear wall.  This braced wall can resist 5,624 pounds of force (380 pounds per foot shear wall capacity times 14.8 feet of shear wall).  The table also requires that 10 L90s need to be installed to match the strength of the shear wall.  If L90’s are installed 16 inches o.c. on a 24 foot long wall, 18 connectors will be required with a capacity of 10,800 pounds.  Because the shear wall will fail once the earthquake forces exceed 5624 pounds, the 4800 pounds provided by 8 of the L90’s are redundant and their installation will add an unnecessary expense to the project.

There is absolutely no reason to recommend both the L70 and the L90 as alternate hardwares as recommended in the Plan Set.  The L90 is about the same price as the L70 and is much stronger.  Overall, the L70 is more labor intensive and thus more expensive to use and I see no reason to recommend its use.

image-11

Retrofit Guidelines for single top plate splice

It must be noted that existing framing conditions require the use of many more Simpson products besides the L90.  In my business, I use 4 other Simpson products to tie framing members together besides the L90.  I even use one that is made by a sheet metal shop because no manufacturer makes what I need.  For the Plan Set to only allow one type of hardware puts extreme limitations on the applicability of the Plans Set.

Retrofit Guidelines for double top plate spliceThis detail illustrates bridging a gap in a cripple wall double top plate that I have never seen.  Actual houses do not have breaks in double top plates that look like this.  I recommend eliminating this detail from the Plan Set.  We do see situations where a vent or drain pipe cuts through both top plates such that a strap will never work because of compression forces.  In this case a 2 by 4 needs to be used to straddle that gap so that the continuity tie works in compression and tension.
This detail illustrates a corrected serious structural deficiency I have seen many times.  This detail should remain as part of the Plan Set.
Drawing: Retrofit Guidelines Foundation BoltingThe arrow points to a section of the detail that says “New cripple stud nailed to existing with 16d common nails at 8” o.c.  The American Plywood Association recommends that this connection be made with 12d common nails because 16d common nails tend to split the wood and all nail guns shoot the slightly smaller in diameter 12d common nail.  Many nail guns do not shoot the 16d common.  This detail should be changed to say 12d common rather than 16d common.

Retrofit Guidelines: Blocking of retrofit shear wall

In the PANEL CUTOUTS detail it shows framing modifications around the vents.  This is a very labor-intensive process. Whenever it is used the Plan Set also requires that the plywood length along the wall be increased.  The Plan Set also specifies that in no case shall the ventilation be reduced.  If a house has 4 vents across the front of the house it will be very labor intensive to install the necessary framing around the vents; and adding extra linear footage may make the retrofit impossible. It is much easier and quite effective just to drill ventilation holes in the plywood at vent locations.  This does not seriously reduce the strength of the shear walls.

PANEL NOTCHING Nail stops for shear wall nailing in Retrofit Guidelines

The PANEL NOTCHING detail is to be used in the event wires are set back into notches in the wall framing.  The nail stops illustrated above are supposed to prevent nails shot by a nail gun from penetrating through the plywood and into the wires.  The problem is that 16 gage nail stops DO NOT resist penetration of nails shot by a nail gun. Recommending the use of nail stops only gives people a false sense of security and will actually increase the likelihood of nails penetrating the wires. This detail should be eliminated and a written warning issued in the Plan Set telling contractors to be careful about shooting nails through wires.

 TECHNICAL NOTES

1. THIS PRESCRIPTIVE PLAN ADDRESSES ONLY SEISMIC STRENGTHENING WORK.  ALTERNATIVE DESIGNS WILL BE CONSIDERED ON A CASE-BY-CASE BASIS.  WORK DONE UNDER PERMIT PURSUANT TO THIS PRESCRIPTIVE PLAN DOES NOT LEGALIZE ANY PREVIOUS WORK DONE WITHOUT A PERMIT.

2. ALL EXISTING CONCRETE AND WOOD MATERIAL WHICH WILL BE PART OF THE STRENGTHENING WORK SHALL BE IN SOUND CONDITION AND FREE FROM DEFECTS WHICH WOULD SUBSTANTIALLY REDUCE THE CAPACITY OF THE MATERIAL.  ANY SUBSTANDARD MATERIAL SHALL BE REPAIRED OR REPLACED TO MEET MINIMUM BUILDING CODE REQUIREMENTS.

There is no information available to the public to help contractors, city inspectors, or homeowners determine the soundness of existing concrete. This should be provided. See APPENDIX G from the Structural Engineer’s Association of Southern California.

  1. NEW FOUNDATIONS SHALL MEET CURRENT CALIFORNIA BUILDING CODE REQUIREMENTS.
    It is redundant to say this.  If a permit is issued this will occur automatically.
  1. NEW MUD SILL PLATES SHALL BE PRESSURE-TREATED DOUGLAS-FIR OR FOUNDATION-GRADE REDWOOD.Foundation grade redwood, which is another name for old growth redwood with a growth ring count of 6-40 rings per inch is a special order item and costs 3 times as much as         pressure treated Douglas fir. It is never used and there is no reason to mention it. In addition, plywood shear walls nailed into redwood are weaker than those nailed to Douglas fir.  I called Ashby lumber, a local lumber yard, and they said they have never sold any and were not even sure they could order it.  They also said that it would be extremely expensive because such quality is only found in old growth redwood.
  1. AN EXISTING SINGLE TOP PLATE MAY BE USED WHEN A 16 GA. METAL STRAP IS PROVIDED WITH 14-8d COMMON NAILS ON EACH SIDE OF THE
    JOINT.
  2. IF SPLICES IN DOUBLE TOP PLATES DO NOT HAVE A MINIMUM 48″ LAP, PROVIDE MINIMUM 4′ STRAP AS ABOVE.
    This is the most expensive way to make this connection. Using nails alone to connect the two top plates together on either side of the break with a nail gun is a much cheaper and more effective way of making this connection.
  1. 7.        WHERE PLATE STRAPS OCCUR WITHIN A BRACED PANEL, THE STRAP SHALL BE PLACED OVER THE PLYWOOD AND THE PLYWOOD NAILS OMITTED WHERE THE STRAP IS INSTALLED.

This is a poor way to make this connection.  Any engineer knows that an independent set of connectors is needed across each shear plane; one set of connectors from the plywood to the top plate and another set of connectors from the steel strap to the plywood.  This detail does not recognize this fact.

  1. 8.        NEW STEEL BOLTS SHALL CONFORM TO ASTM A307.  All bolts found at any lumber year and Home Depot are ASTM A307.  This term is meaningless to people reading the Plan Set so there is no reason to mention it. EPOXY BOLTS AND EXPANSION BOLTS SHALL BE INSTALLED PER MANUFACTURER’S INSTRUCTIONS.  It needs to be made clear here that 5/8 wedge anchors cannot be used for retrofit applications.  See APPENDIX I.  AND IN ACCORDANCE WITH THE PROVISIONS OF AN APPROVED NATIONALLY RECOGNIZED TESTING AGENCY.  NO THIRD PARTY SPECIAL INSPECTIONS ARE REQUIRED.  EXPANSION BOLTS SHALL NOT BE USED WHEN THE INSTALLATION CAUSES CRACKING OFTHE FOUNDATION WALL AT THE LOCATION OF THE BOLT.  Mention should also be made that bolts shall not be installed within a certain distance of any existing cracks.  Information should also be given concerning the pros and cons of various bolt fasteners, some of which are not mentioned in the Plan Set.  Please see APPENDIX I.   

9.   ALL METAL CONNECTORS AND HARDWARE SHALL MEET AN APPROVED STANDARD FOR ITS INTENDED USE AND BE INSTALLED PER MANUFACTURER’S INSTRUCTIONS, AND IN ACCORDANCE WITH THE REQUIREMENTS OF THESE STANDARDS.  ALTERNATE DETAILS MAY BE APPROVED BY THE BUILDING OFFICIAL PROVIDED DETAILED INFORMATION   AND CALCULATIONS ARE SUBMITTED AND APPROVED.

10.   WHERE AN EXISTING CONTINUOUS RIM JOIST, END JOIST, OR SOLID BLOCKING BETWEEN JOISTS, DOES NOT EXIST ABOVE THE PERIMETER CRIPPLE WALL OR MUD   SILL, NEW BLOCKING AND/OR SUPPLEMENTAL CONNECTIONS SHALL BE PROVIDED AND SUBJECT TO APPROVAL BY THE BUILDING   OFFICIAL.

  1. UNDERFLOOR VENTILATION SHALL BE MAINTAINED.

This sometimes makes it difficult and expensive to install the proper linear footage of plywood.  Holes should be drilled in the plywood to provide the required ventilation. 

  1. DUE TO THE CORROSIVE NATURE OF NEW PRESSURE TREATED WOOD USED AFTER 1-1-04 AND TO PREVENT PREMATURE FAILURE OF THE METAL HARDWARE, FASTENERS IN NEW PRESSURE TREATED WOOD SHALL BE HOT DIPPED GALVANIZED FASTENERS (MEETING ASTM A  153) AND CONNECTORS (ASTM  A 653 CLASS G185 SHEET), OR BETTER.

In retrofit work, new pressure treated wood is usually installed in very dry locations under the house. The chemical manufacturers of the pressure treated wood do not require galvanized fasteners in dry locations. Please see APPENDIX H.  ASTM specifications will be meaningless to the users of this document. Most users will not even know what ASTM (American Society of Testing Materials) stands for.     

 

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