Carriage Bolts And Deck Attachments - Follow Up

Home Inspector with Jay Markanich Real Estate Inspections, LLC 3380-000723

A couple of weeks ago I had two posts about carriage bolts and deck attachments.  I had written Simpson Strong Tie with some questions as some information I received in a seminar was not completely understood.

In the seminar they had suggested that carriage bolts should not be used in deck attachments, particularly guardrail posts.  The reason, as I understood, was that the connection can weaken overtime as the wood shrinks, and when tightened they can be drawn into the wood, further weakening the attachment.

Yesterday I received a very kind, and long, phone call from a Simpson engineer.  He went over my questions individually and we had a very nice discussion.  These were my questions, as written, to Simpson:

1. My deck is 13 1/2 years old and carriage bolts were used everywhere. I do tighten them periodically and the heads have been sucked into the wood somewhat. None is weak or wobbly. At what point do these bolts become an issue?
2. How much of an issue is it really, unless the posts, et al, get loose? I don't know what to tell my clients!
3. Should they be replaced with a proper through bolt and washer arrangement?

4. Will codes begin to reflect this information?

This is a carriage bolt and the thing in question.  It comes in various lengths and is characterized by its round head and square shank under the head.  These bolts have been used for years to attach deck guardrail posts to decks, and decks to houses!  These bolts are used all over the country.

The engineer, David F., began by saying that Simpson Strong Tie has a general concern, which they mention in their education classes.  They are about designing and testing attachments and producing holders and an array of other things mentioned in my previous post. 

They do not produce nuts and bolts and washers, so it isn't that they are bashing one attachment, like carriage bolts, in favor of one of their products.

David further said that the actual EFFECT of using carriage bolts, as opposed to washers and through bolts, is UNKNOWN.  They are devising tests now to determine that EFFECT.  As engineers, they are interested in DATA!

The American Wood Council puts out what is essentially a code book for engineers and wood designs.  The information is called the National Design Standard.  In that standard it does not mention carriage bolts as meeting the standards of the American Society of Mechanical Engineers (ASME).  The NDS is the information from which local codes are developed and implemented.

Here is the issue.  The through bolt and carriage bolt are essentially the same steel "dowel."  They have the same strength.

The problem comes with the head.  The 1/2" carriage bolt head has 35% less BEARING AREA than the standard 1 3/8" washer under a 1/2" through bolt's ending nut.

The head of the carriage bolt is what takes the force if a guardrail post is pushed out.  It is the head, or the washer with a through bolt, that takes the brunt of the force.  Having less surface area A CARRIAGE BOLT HEAD IS SIMPLY ABLE TO WITHSTAND LESS FORCE.

How much less force?  That is what they are trying to determine!  Until that is determined ASME cannot cover carriage bolts in any standard.  Nor can a new product be designed.

Always thinking I asked why they don't just design a carriage bolt with more surface area.  That leads to the second concern.

A carriage bolt can only be tightened so much.  Eventually the head will spin due to tension and it cannot be tightened any more.  There is nothing to grip on both ends, so friction takes over.  A through bolt with its washer, as shown above, can be held with a wrench on both ends and can always be tightened further.

Again, always thinking, I suggested that they design a carriage bolt with a larger head with a square or Allen-wrench hole in it so it can be held in place and tightened without spinning!  I think they should design it and call it the Jay Bolt!   I'm wondering if right now he is thinking, "Hmmmm!?"

I appreciated David's willingness to call me and speak with me about this.  I think he said they have never gotten a response or a question from a home inspector before!  He was glad to do it. 

My recommendation:  when you don't know something, try to find out!  You can't always get what you want, but if you try, sometimes, you just might find, you get what you need!  So go, and do that voodoo that you do so well...


Posted by

Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560


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Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

When I have my island in the Caribbean, you can come visit Debbie...

That may be a while from now however!  Maybe I could hire someone who knows about marketing?

Jun 14, 2011 11:49 PM #8
Anne M. Costello
Weidel Realtors - Yardley, PA

Jay: I am rooting for the Jay Bolt. I agree it was great that the company answered your questions via telephone, as opposed to an email. It provided a chance for a great dialogue. Keep us posted as you learn more.

Jun 15, 2011 12:21 AM #9
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

And we had a great dialogue Anne, which he encouraged me to continue when I have questions.  I was pretty sure they would get back to me, just not by telephone!

Jun 15, 2011 12:41 AM #10
Sally K. & David L. Hanson
EXP Realty 414-525-0563 - Brookfield, WI
WI Realtors - Luxury - Divorce

The JAYMAR...attaches anything, anywhere for a lifetime.....and you live off the patent/production residuals...sounds like a plan !

Jun 15, 2011 01:15 AM #11
Tish Lloyd
BlueCoast Realty Corporation - Wilmington, NC
Broker - Wilmington NC and Surrounding Beaches

And here I was scrolling quickly to find Bill's response to this -- very impressive to know you have taken this to the next level for your "followers"; thank you. 

Jun 15, 2011 01:26 AM #12
Don MacLean
New England Real Estate Center Inc. - Easton, MA
Realtor-Homes for Sale- Easton Mass

Jay, I would not had expected the difference to be 35%. But we have all learned a lesson here, the answer can and will be found if we just take the next step to get it.

Enjoy the day

Jun 15, 2011 02:14 AM #13
Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Jay to compensate for the washer I guess you might be able to use a larger bolt.  I have a sense that in this application the likelihood of creating a failure situation would be pretty slim.  Also here is a trick for a spinning carriage bolt---either installing or uninstalling.  Take a hack saw and cut a small groove in the head for a screw driver blade to fit in.

Jun 15, 2011 02:41 AM #14
Steven L. Smith
King of the House Home Inspection, Inc. - Bellingham, WA
Bellingham WA Home Inspector


ARound here we almost never see bolts, lag bolts, per the basic code IRC

Jun 15, 2011 03:20 AM #15
Al & Peggy Cunningham, Brokers
RE/MAX West Realty Inc., Brokerage - Brampton, ON
Our Family Wants To Help Your Family!

Jay in our humble opinion, the carriage bolt should be used when the square under the head fits into a square hole, always thought that was what they were for.  Bolts and washers to be used otherwise.

Jun 15, 2011 03:27 AM #16
Robert Butler
Aspect Inspection - Montreal West Island, QC
Montreal Home Inspector | Aspect Inspection

Now that you've mentioned your 'Jay Bolt' idea, I think you're too late. It's out there. Same idea with an alan head socket in the centre face head of the bolt.

This allows you to hold the head against spinning and tighten the nut. This design keeps the low friction profile of the head that is important in exposed applications.

Charlies idea, comment 14, is good for existing stock maintenance, just file off any burrs that might result.

Jun 15, 2011 04:05 AM #17
Jack Gilleland
Home Inspection and Investor Services, Clayton - Clayton, OH

Good idea Jay, whether there is one already out there or not.

Jun 15, 2011 06:51 AM #18
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Good info. I will have to bring this up next month when the Simpson rep comes to our monthly ASHI meeting.

Jun 15, 2011 12:12 PM #19
John Mulkey - Waleska, GA
Housing Guru

Jay - I can see Billy Jays hawking "J" bolts.  "And if you order right now,'cause we can't do this all day, we'll double the order--just pay extra shipping and handling."  It's a natural for Billy.


Jun 15, 2011 12:31 PM #20
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC


Fun read. It really is amazing hoe much leg (lags) this story gotten ; )

Jun 15, 2011 06:42 PM #21
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

They still haven't gotten back to me with how the idea is progressing S&D, but I'll let you know!

Tish - I have often contacted experts for information when I don't know something.

Well, I didn't either Don, and that is the kind of statistic you would expect to come from engineers!

Charlie - my recommendation to them was a beefier bolt, 1 1/2" in diameter.  Your scratching the end is pretty labor intensive.  In my production factory maybe we could employ thousands of 12 year-old Malasian girls* with hack saws to give the round heads that screw-driver ready look!

* Why not?  The electronics manufacturers do!  I kind of prefer the hole for an Allen or sqauare wrench though...

Jun 15, 2011 11:02 PM #22
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

And despite that, Steve, around here lags aren't permitted!  Only through bolts.  But carriage bolts are used all over.

A&P - hard to get that square hole on a pressure-treated guardrail post!  But when possible of course!

Robert - the head I proposed is beefier and 1 1/2" in diameter.  I haven't seen that size, but maybe they're out there.  And when is a carriage bolt used when it isn't an "exposed application?!"  Charlie's idea is so labor intensive I had to propose the 12 year old Malasian girl idea!

I doubt anything will come of it Jack.  Maybe I need a good marketing agent.  You available?

Jun 15, 2011 11:06 PM #23
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

I'd love to be a fly on the wall there Jim!  I bet his answer is the same, but lemmino!

John - he is on it I am sure.  But his products are usually "improvements" on ideas, and not so much a new product.  The Jay Bolt would be an improvement without the quotations!

Don - gotta wonder how carriage bolts got their name.  Probably 150 years ago they were used for carriages!  Jay Bolts, of course, would only be used by people named Jay...

Jun 15, 2011 11:08 PM #24
Bill Saunders, Realtor®
Meyers Realty - Hot Springs, AR

Jay, as always, an informative post. I am thinking the "Jay" bolt sounds too simple...something like the markanich tension connector might be worth more... especially for government contracts. :). (A smaller similar device could be sold separately for those Billy Jay gutter gardens...


Jun 16, 2011 04:41 AM #25
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

It's impressive, Bill, that you remember the famous Get Yer Gutter Garden! product!  Actually, interestingly, the Simpson engineer called me this morning to say that this bolt is a good idea!  He is sending it on to product development to see what they think.

Jun 16, 2011 05:46 AM #26
Jack Gilleland
Home Inspection and Investor Services, Clayton - Clayton, OH

Jay, I'm always available for the right price, but sadly you can do better than me for marketing.

Jun 16, 2011 06:40 AM #27
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