# Decking beams and joists for perpendicular decking



## Gary Cornelisse (Apr 24, 2017)

I'm planning to lay my decking perpendicular to the house instead of parallel.  I've been through the DCA 6 several times, and despite what our local code officer said, it's not clear how to figure out the specs for my beams and joists.  Table 3 in the DCA is for joists framing from one side only.  If my beams are extending from the ledger and I'm running joists between the beams (parallel to the house), it has to be framing from two sides of the beams.

I was hoping someone could point out the relevant sections of the DCA  or help me figure out the necessary spec to meet code requirements.

- Basic deck dimensions are 20'x40', 40' side against the house
- Beams and joists will be 2"x10" Southern Pine
- 6"x6" posts at 10' and 20' from house

- 2 or 3 -  2"x10's" for a beam?
- Spacing (joist spans) between beams?

Any help is appreciated. Thank you!


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## cda (Apr 24, 2017)

Welcome


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## north star (Apr 25, 2017)

*~ # ~*

Gary,

Another Welcome to The Building Codes Forum !

On Page 19 and following; of the DCA 6 Guide, it lists the span
distances........Also, the American Wood Council ( AWC ) has an
online calculator for use in determining the correct spans for each
wood species and size of joists used.

Here is a Link to the AWC:
*http://www.awc.org/codes-standards/spantables*

At the top of the page are the Links to the calculators for use
and the span tables.

*~ # ~*


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## steveray (Apr 25, 2017)

You are going to need piers and posts at the house if you are running the beams perpendicular (or bear on the existing foundation)....so you can run the joists parallel...so you can run the decking perpendicular....


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## Gary Cornelisse (Apr 25, 2017)

Thank you!  I'll take a look at this new info.


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## jar546 (Mar 10, 2020)

Glen where are you?


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## Pcinspector1 (Mar 10, 2020)

I think he's trying to get yellow highlighter out of an old code book!


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## e hilton (Mar 10, 2020)

Saturn2020 said:


> , is there any difference if the decking is laid perpendicular or parallel?


As long as you honor the span limits of the product and adjust the joist spacing as needed, the choice of direction is cosmetic.  If you’re on a budget, normal 5/4”x6 deck boards will be the least expensive, followed by 2x boards.


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## Glenn (Mar 11, 2020)

There are a number of things to respond to.

1) Where the beams bear their concentrated load at the house, you cannot transfer this load through a ledger attached with any prescriptive means (IRC or DCA-6).  Those concentrated loads are not accounted for.  In this design you essentially do not have a ledger.  You will need to either have a connection engineered or extend the beams into your house and bear them with support directly below (stud post or foundation).  FLASH THIS LIKE YOU HAVE NEVER FLASHED BEFORE!!  INSANE DETAILING AND CARE.  You also need to be sure you have significant lateral restraint at the house at each beam, as you have no ledger fasteners providing this resistance.

2) The reason you cant support the beam from both sides is simply because the engineering in the span table does not account for this.  There is a way to do this, but it is outside of the code.  It does meet the intent of the code, however.  See my course Down the Load Path at www.buildingcodecollege.com for details.  You can take the course fro free without the coupon code "welcome"  If you are building a deck, I suggest you purchase the other three deck courses as well (if you find the free one of value).

3) There would be nothing unusual about your joist span in this design.

4) You absolutely must understand that you are undertaking a much more difficult design and project with beams/joists in this orientation.  This is not recommended for non-studied DIY'ers.  It most certainly can be done, but I caution you that what you are intending is not very standardized.

I hope this helps.


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## Glenn (Mar 11, 2020)

jar546 said:


> Glen where are you?


Just got home from traveling and teaching for the last week and a half.  Now my future events are being corona'd.  (cancelled)


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## Rick18071 (Mar 11, 2020)

Just got concert tickets for Santana/ Earth, Wind and Fire in August. I hope the this virus is over by then.


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## ADAguy (Mar 13, 2020)

Likewise


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## e hilton (Mar 15, 2020)

Rick18071 said:


> Just got concert tickets for Santana/ Earth, Wind and Fire in August. I hope the this virus is over by then.


You better hope so.  The band and most of the audience are in the age group that is most at risk.


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## ADAguy (Mar 18, 2020)

Too true but way to reduce SS payments (smiling) for future generations.


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## e hilton (Mar 18, 2020)

This whole event might be natures way of thinning the herd.


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## JPohling (Mar 18, 2020)

My Stones concert was cancelled.................


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## ADAguy (Mar 24, 2020)

Mick is a senior and recovering from heart surgery, think he isn't a candidate for avoiding crowds?


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## Min&Max (Apr 9, 2020)

Gary I am curious as to how far out of the ground you are with your deck.


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