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Old 05-18-2013, 02:47 PM   #1
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Deck Framing Question


I am in the planning stages for a partially covered deck. It will be 20' x 16' connected to the house frame. I put together my plan for structure and then sent it to an architect I am acquainted with to get their nod that it is strong enough to support the deck and roof. I'm confident it will be, as I followed the AWC recommendations for a combined deck and roof load expectancy.

I'm having trouble finding the proper framing technique when a deck column extends up through the decking toward the roof. Everything I've found indicates that the beam and joists should rest on top of any posts, but when the column has to extend to the roof, I don't see how that's possible. Everything I've read indicates sandwiching deck beams around the post is a no-no, so that's not a choice. The plan was to use dropped beams with which the joists would rest on. If go the stacked route, it would be concrete-post-beam-rim joist-post-roof. That seems like a whole lot of connection points. I know Simpsons are strong, but that just seems like too many.

Here is an image that might better articulate my question.



I'm seeking to learn and I am getting my structure approved, so assume that everything is structurally sound and I have my permit in hand. Which will both be true before I start this endeavor.

Thanks!

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Old 05-18-2013, 03:14 PM   #2
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Welcome to the Forum!

you may want to edit your profile to include your location as many times answers to questions depend on your location.

Silly question .... not trying to bust ya chops, if you're using an architect why isn't the architect doing the design and sizing structural elements?

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Old 05-18-2013, 03:19 PM   #3
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Welcome to the Forum!

you may want to edit your profile to include your location as many times answers to questions depend on your location.

Silly question .... not trying to bust ya chops, if you're using an architect why isn't the architect doing the design and sizing structural elements?

Thanks. I added my location (East TN).

As for your second question, because I'm using a friend that is an architect. I prefer not to abuse my friends, instead doing a lot of the leg work myself and then seeking their input. I have an engineering degree, though I don't practice structural engineering. I know enough to calculate load levels and read span charts. The architect is just looking it over before I submit it to the city to make sure I didn't do something obviously wrong.

This is more of an execution style question. When I started "building it in my head" my brain kind said "uh, how do we connect the beams when the column doesn't cap?" When Google failed me (and there was much Googling) I came here with specifics.
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Old 05-18-2013, 03:22 PM   #4
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Oh and I found this thread: Attaching Porch Column to a flush beam that was very similar to what input I'm seeking. The design I came up with is drop beam though, so it it's just different enough that it didn't answer my question. I guess I could recalculate for flush beams, but...now I just really want to know. I like knowing and understanding.
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Old 05-18-2013, 04:17 PM   #5
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as I followed the AWC recommendations for a combined deck and roof load expectancy.
if you are talking about the AWC's "Prescriptive Residential Wood Deck Construction Guide" this does not address having a roof over a deck. It strictly addresses the design and construction of a deck using prescriptive methods and does not account for the loads developed in the roof assembly.

A wood beam to wood column connection can be made by either notching the column so that the beam can bear upon the column or the beam can be made the same size as the column so that it sits on top of the column and metal connectors such as the ones you mentioned are used to connect the beam to the column. Some connectors allow for different sizes of beams and columns so they are not required to have the same thickness. Of course notching a column reduces the lateral loads it can withstand.

Typically building codes require a minimum of 1-1/2" of bearing on wood or metal for most joists/rafters/beams and girders. Depending on the actual loads this bearing area may need to be larger to prevent crushing of wood fibers.

Choices for flush or drop beams depends many times on headroom and lateral bracing requirements. Also span of joists can come into play.

Is this a roof over a deck, or a deck over a roof, not sure from your sketch?

A roof over a deck must account for the wind and seismic loads (lateral loads) developed and any gravity loads. These loads must be transferred to the ground or foundation. A means of resisting the lateral loads must be determined. This is where lateral bracing can come into play.

I do not know of any prescriptive porch roof design manuals, I have made a suggestion to the American Wood Council about developing one. Of course prescriptive manuals are a lot more restrictive than an engineered design typically as they have to account for many variables.

Lastly an internet forum is not a good place to seek structural design thus my reason for asking about your friend the architect. You do not know the level of education and experience of people providing you answers such as myself.

Not sure if this has been of much help or not, but I do wish you the best with your project.
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Old 05-18-2013, 04:26 PM   #6
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Thank you for the information. Interesting that it doesn't account for something that I would see as common. I wish my city had been more forthecoming with information.

To answer your one question, it's a gable roof over a deck that will be tied into the existing structure. The trusses will be manufactured, and then built on headers and tied into the existing roof via a cricket style. Fortunately both seismic and wind requirements are low in my area.
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Old 05-18-2013, 04:43 PM   #7
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could look into a post and beam type construction as it sounds like you need something to support the trusses on. A lot of typical porches are built this way with a beam attached to columns, and the roof assembly attached to the beam.
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Old 05-18-2013, 08:28 PM   #8
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could look into a post and beam type construction as it sounds like you need something to support the trusses on. A lot of typical porches are built this way with a beam attached to columns, and the roof assembly attached to the beam.
The first image on this page shows the basic design for the trussed roof. The columns will go up 8' from the deck floor and attach to a beam that connects each post and ties into the wall top plate. The trusses will rest on the beam.

http://www.chiefarchitect.com/suppor...?faqNumber=598

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