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Deck Connections
- Thread starter Big Mac
- Start date
JBI
REGISTERED
I'm not.
But, I'm not doing direct enforcement anymore. ;-)
But, I'm not doing direct enforcement anymore. ;-)
Architect1281
REGISTERED
Sometimes we Get them sometimes we don't /
why ? because as it's worded IMHO I can't demand them - just engineering proof if they dont.
the shall be permitted per .... is the key. If I say put them in then I'm the designer not the approver.
and the "not less than 2?? what where and how far apart 2 on a 10 foot deck or 2 on a 40 foot deck.
How wide are those deck 8', 10', 16'. Sounds like someone who was sure of how to build every deck possible.
stupid english IMHO.
R502.2.2.3 Deck lateral load connection. The lateral load connection required by Section R502.2.2 shall be permitted
to be in accordance with Figure R502.2.2.3. Hold-down tension devices shall be installed in not less than two locations
per deck, and each device shall have an allowable stress design capacity of not less than 1500 pounds (6672 N).
why ? because as it's worded IMHO I can't demand them - just engineering proof if they dont.
the shall be permitted per .... is the key. If I say put them in then I'm the designer not the approver.
and the "not less than 2?? what where and how far apart 2 on a 10 foot deck or 2 on a 40 foot deck.
How wide are those deck 8', 10', 16'. Sounds like someone who was sure of how to build every deck possible.
stupid english IMHO.
R502.2.2.3 Deck lateral load connection. The lateral load connection required by Section R502.2.2 shall be permitted
to be in accordance with Figure R502.2.2.3. Hold-down tension devices shall be installed in not less than two locations
per deck, and each device shall have an allowable stress design capacity of not less than 1500 pounds (6672 N).
Francis Vineyard
REGISTERED
Agree with Architect1281; it's an acceptable design method when applicable or required such as high wind or load. This has been discussed before;
http://www.inspectpa.com/forum/showthread.php?3520-Lateral-load-connectors&highlight=r502.2.2.3
http://www.inspectpa.com/forum/showthread.php?3520-Lateral-load-connectors&highlight=r502.2.2.3
NH09
REGISTERED
I also agree, if the other ledger bolting requirements have been met I do not ask for them.
Deck Connections
Follow-up question.
To those of you who replied, or any other forum members for that matter, are any of you in a highly active seismic area, high wind area or flood prone areas, and would that have any impact on your answer?
Follow-up question.
To those of you who replied, or any other forum members for that matter, are any of you in a highly active seismic area, high wind area or flood prone areas, and would that have any impact on your answer?
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dhengr
Bronze Member
Read the thread that FrancisV shows a link for in post #4 abv., in particular posts #38 & 41 if you want part of my take on the question. I’m still waiting for someone to post the applicable code sections and figures, since I don’t have a copy of the 2009 IRC.
BigMac.... certainly the type of loading influences the lateral loads on the deck. Wind loading involves wind pressures positive and negative, a function of wind speed, on projected surface areas; and its resultant acts at the centroid of the projected areas. It is basically treated as a short duration static load at that centroid. Earthquake forces act on the mass of the deck, at the center of mass of the deck, and may act in any direction, in a very dynamic fashion. While floods would act on any projected area of the structure exposed to the onrushing water’s force. All of these can act in most any direction and at some point, or in a line of action, some distance removed from the ledger or other attachment to the house. Thus, they will cause shearing forces in the plane of the ledger or wall of the house; but in addition, since their resultant acts at a centroid point removed from the house, they will also cause a moment, a twisting force couple, trying to wrench the deck diaphragm away from the house. There will be a tension force at one corner of the deck and a compression force at the other corner, the moment couple, due to this twisting action. And, since we don’t know which direction the force may come from, either corner can be the tension corner. I suspect the 1500# and the hardware are intended to counteract the above. IF they are needed.
Maybe with the next edition of the IRC they can come out with an additional 600 or 800 page volume which defines exactly when these things should be considered and when they are needed; depending on the day of the week, the sky color, local altitude, siding color, and such like.
BigMac.... certainly the type of loading influences the lateral loads on the deck. Wind loading involves wind pressures positive and negative, a function of wind speed, on projected surface areas; and its resultant acts at the centroid of the projected areas. It is basically treated as a short duration static load at that centroid. Earthquake forces act on the mass of the deck, at the center of mass of the deck, and may act in any direction, in a very dynamic fashion. While floods would act on any projected area of the structure exposed to the onrushing water’s force. All of these can act in most any direction and at some point, or in a line of action, some distance removed from the ledger or other attachment to the house. Thus, they will cause shearing forces in the plane of the ledger or wall of the house; but in addition, since their resultant acts at a centroid point removed from the house, they will also cause a moment, a twisting force couple, trying to wrench the deck diaphragm away from the house. There will be a tension force at one corner of the deck and a compression force at the other corner, the moment couple, due to this twisting action. And, since we don’t know which direction the force may come from, either corner can be the tension corner. I suspect the 1500# and the hardware are intended to counteract the above. IF they are needed.
Maybe with the next edition of the IRC they can come out with an additional 600 or 800 page volume which defines exactly when these things should be considered and when they are needed; depending on the day of the week, the sky color, local altitude, siding color, and such like.
Francis Vineyard
REGISTERED
Here's link to the 2009 Virginia IRC; Virginia amended the ICC version where there is a double bar in the margin. The single bars are the changes made from the previous 2006 version.dhengr said:
http://ecodes.biz/ecodes_support/free_resources/Virginia2009/09Residential/PDFs/Chapter%205_Floors.pdf
R502.2.2 Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable.
Consider how the deck as a whole is assembled to resist the lateral forces imposed on the floor.
Do the combination of post thickness and height subject to bending and warpage; are there diagonal (knee) braces for both directions; perpendicular and parallel? Is the decking diagonal to the joist? Do the beam and joist attachments resist roll-over?
Another good article on the subject;
http://www.deckmagazine.com/article/252.html
Dick it still wouldn't solve the problem of lack of training and funding for small jurisdictions. Some of us can't keep up with the changes.dhengr said:
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This month's rash of tornadoes should help us understand that we cannot design structures that resist natural forces.
I am happy with decks that fail in earthquakes, tornadoes, hurricanes, floods, snow, or just after 10 years of sitting there. While I suspect my house will survive 10 years of lack of attention, I know that the other 5 events could destroy my entire house.
And I sleep well inside my house every night.
I am happy with decks that fail in earthquakes, tornadoes, hurricanes, floods, snow, or just after 10 years of sitting there. While I suspect my house will survive 10 years of lack of attention, I know that the other 5 events could destroy my entire house.
And I sleep well inside my house every night.
Deck Connections
As I understand it the 1500# holddowns were introduced into the code by FEMA. If that is the case, it would seem that it is a reaction to natural disaster type scenarios. I can't help but wonder if the 1500# holdown is actually a more important factor when adding a deck to an exisiting house. If so, it could be an attempt to deal with situations where we have no real clear cut way to know what exisits to anchor a deck to. The holddowns would then be placed so we would not need to rely exclusively on a potentially rotten rim joist, or maybe just sheathing to support the new deck. I have also seen cases where I-joist were used and solid blocks placed between them to keep the I-joist from rolling sideways. Though the blocking may accomplish that task, it certainly would not make for a solid system for which to attach a deck. For that matter I have seen cases where the workmanship was so poor that a floor joist system even with the proper rim joist still wasn't nailed in a fashion that would adequately anchor the deck to the floor diaphragm. The inclusion of the 1500# holddowns is an attempt to get the deck anchored in a substantial fashion back to the floor diaphragm of the house.
Even a solid deck anchored to garbage makes for an inadequate system, even without consideration for excessive wind, seismic, or flooding.
The code actually that if a solid connection cannot be verified, the deck is required to be a freestanding deck. Currently I know of no jurisdiction that is willing to ask the applicant to expose the framing and/or make an extra trip tot he job site to ensure that a sloid anchor is possible.
As I understand it the 1500# holddowns were introduced into the code by FEMA. If that is the case, it would seem that it is a reaction to natural disaster type scenarios. I can't help but wonder if the 1500# holdown is actually a more important factor when adding a deck to an exisiting house. If so, it could be an attempt to deal with situations where we have no real clear cut way to know what exisits to anchor a deck to. The holddowns would then be placed so we would not need to rely exclusively on a potentially rotten rim joist, or maybe just sheathing to support the new deck. I have also seen cases where I-joist were used and solid blocks placed between them to keep the I-joist from rolling sideways. Though the blocking may accomplish that task, it certainly would not make for a solid system for which to attach a deck. For that matter I have seen cases where the workmanship was so poor that a floor joist system even with the proper rim joist still wasn't nailed in a fashion that would adequately anchor the deck to the floor diaphragm. The inclusion of the 1500# holddowns is an attempt to get the deck anchored in a substantial fashion back to the floor diaphragm of the house.
Even a solid deck anchored to garbage makes for an inadequate system, even without consideration for excessive wind, seismic, or flooding.
The code actually that if a solid connection cannot be verified, the deck is required to be a freestanding deck. Currently I know of no jurisdiction that is willing to ask the applicant to expose the framing and/or make an extra trip tot he job site to ensure that a sloid anchor is possible.