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Old 04-25-2013, 04:24 PM   #1
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32" cantilever BEAM Double 2x10 on a 19' run??


am going to scan a drawing in if needed, and sorry for another cantilever post. I am having a really hard time deciding if this is OK.


To keep it simple:

my deck is 19' wide x 12ft long.

I have 4 6x6 support posts around 5.5ft apart so span is about that.
My Beam/posts sit at the 10ft mark away from the house, then joist continue to 12ft.

The big question: Can I cantilever my support BEAM qty=2 (2x10) 32" over the support BEAM on one side???


extra info: my joist are 2x10' @16 centers, 6x6 corner rail posts. the beam consists of 2 2x10's treated, they were 20ft boards so all one board across.

considerations: additional support putting a 4x4 or 6x6 @45 degree from the end of beam cantilever (32" mark) down to support post, then back up from other side if necessary to bring side load back to beam. ??

thanks for any good info. I don't want to cut any corners on this deck but this spot is giving me some question.
SHOULD i swap my 2 beams to 2x12's instead of 2x10's? it will be some work but will if suggested.









Last edited by csmonte; 04-26-2013 at 03:58 PM. Reason: adding information
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Old 04-25-2013, 07:54 PM   #2
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32" cantilever BEAM Double 2x10 on a 19' run??


Why dont you run your joists the 12 foot direction?

As to the 2 x 2x10 (2) 2x's only gives you 3 inches of bearing surface, which is fairly easy to roll. If I had a choice, I would go with (3) 2 x10 to make up a girder, not 2.

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Old 04-25-2013, 08:14 PM   #3
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32" cantilever BEAM Double 2x10 on a 19' run??


a 2 ply 2x10 isnt a beam its only a header and for a deck thats insufficient it would never pass in most regions. 3ply is minimum code as for the cantilever 32" wont pass either about the most ive ever seen is 12"
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Old 04-25-2013, 08:39 PM   #4
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32" cantilever BEAM Double 2x10 on a 19' run??


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a 2 ply 2x10 isnt a beam its only a header and for a deck thats insufficient it would never pass in most regions. 3ply is minimum code as for the cantilever 32" wont pass either about the most ive ever seen is 12"
I agree with the three ply, but you can cantilever as much as 3 feet in my county. 2 feet is pretty much the norm. Cantilevers work for you as the loads beyond the fulcrum counteracts the inboard loads, but I'm sure you know that.
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Old 04-25-2013, 08:54 PM   #5
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32" cantilever BEAM Double 2x10 on a 19' run??


Quote:
Originally Posted by csmonte View Post
I am going to scan a drawing in if needed, and sorry for another cantilever post. I am having a really hard time deciding if this is OK.


To keep it simple:

my deck is 19' wide x 12ft long.

I have 4 6x6 support posts around 5.5ft apart so span is about that.
My Beam/posts sit at the 10ft mark away from the house, then joist continue to 12ft.

The big question: Can I cantilever my support BEAM qty=2 (2x10) 32" over the support BEAM on one side???


extra info: my joist are 2x10' @16 centers, 6x6 corner rail posts. the beam consists of 2 2x10's treated, they were 20ft boards so all one board across.

considerations: additional support putting a 4x4 or 6x6 @45 degree from the end of beam cantilever (32" mark) down to support post, then back up from other side if necessary to bring side load back to beam. ??

thanks for any good info. I don't want to cut any corners on this deck but this spot is giving me some question.
SHOULD i swap my 2 beams to 2x12's instead of 2x10's? it will be some work but will if suggested.

To clarify your question. You want to extend your 2-2x10's (used as a header) to span 32" over the corner (last) 6x6 wood post?
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Old 04-25-2013, 09:09 PM   #6
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32" cantilever BEAM Double 2x10 on a 19' run??


Post up some blueprints (you'll need them for a permit anyway) and we can help out a little more. Of course in the end the building department is going to have final say as to what you'll be allowed to do.
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Old 04-26-2013, 09:44 AM   #7
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32" cantilever BEAM Double 2x10 on a 19' run??


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I agree with the three ply, but you can cantilever as much as 3 feet in my county. 2 feet is pretty much the norm. Cantilevers work for you as the loads beyond the fulcrum counteracts the inboard loads, but I'm sure you know that.

im fully aware of how it works. but do to lower quality lumber most engineers wont put a stamp on such a large cantilver so they wont allow more than one joist to bear on the cantilvered beam
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Old 04-26-2013, 10:55 AM   #8
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32" cantilever BEAM Double 2x10 on a 19' run??


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Originally Posted by woodworkbykirk View Post
im fully aware of how it works. but do to lower quality lumber most engineers wont put a stamp on such a large cantilver so they wont allow more than one joist to bear on the cantilvered beam
I guess In just not understanding this post at all. When I think of a cantilever on a deck Im thinking a 3 ply main girder set back two feet, or in this case 32 inches with the joists running perpendicular over the girder. If lumber is of such poor quality so as not having the structural capability to support the implied loads, then it cannot be used in simple span or in cantileverd configuration, so I dont get the statement about an engineer being reluctant to stamp drawings. If the engineer specifies no 2 framing lumber, then his calculations are based on the species and stated grade of the lumber. I have never seen an engineer drive to the lumber yard to inspect the lumber on a case by case basis. If the outlet selling the lumber is lying about the grade it would be pretty obvious to someone who knows wood IMHO. I'm not sure what you mean about a cantilevered beam in this particular post, but you might understand the OP better than I. Some people are able to give answers on posts that I find rather cryptic in their lack of detail, like we are supposed to guess about location, size, slope conditions, frost depth, live load, etc. etc. etc.

I do know that you are well versed regarding wood though, from reading your posts.
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Last edited by jagans; 04-26-2013 at 11:01 AM.
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Old 04-26-2013, 02:37 PM   #9
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32" cantilever BEAM Double 2x10 on a 19' run??


Cantilevered beams are tricky to check as you need to consider different loading cases (eg load only on cantilevered part; load only on inner span; load on whole beam).
There will be a significant 'hogging' moment at the support post,which will increase the bending stress in the timber, and increased compressive stress on the fibres directly over the post.
Cantilevers also have a tendency to twist sideways if not adequately braced,
hence the suggestion that twin beams might roll sideways; 3" might not be sufficient to ensure lateral stability.
It's easy to state, but you do need to get an SE to size the beams.
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Old 04-26-2013, 03:35 PM   #10
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32" cantilever BEAM Double 2x10 on a 19' run??


thank you guys a lot for the replies, I'm working on a way to upload some photo's since my flickr account has expired. Soon, I will have some photo's for you guys. thanks again.
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Old 04-26-2013, 04:07 PM   #11
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32" cantilever BEAM Double 2x10 on a 19' run??


Now that I have pictures:

house to beam = 10ft
joist cantilever = 21"

Beam 19ft qty 2 2x10's
span between support posts about 6'4"

cantilever of BEAM (2 2x10's) = 32"

Last edited by csmonte; 04-26-2013 at 04:33 PM.
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Old 04-26-2013, 08:00 PM   #12
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32" cantilever BEAM Double 2x10 on a 19' run??


if you look at the photos. by having the joists cantilever out past the beam and the beam cantilever out so far past the post your placing quite a bit of force on the framing.. if you overload that deck with weight at the outside corner the deck will want to tip which also transfers to the ledger. just think about how the live loads will act on the structure. just because something was done a certain way 40 years ago doesnt mean its acceptible today.. todays construction has way more thought go into it than in the past..

the amount of floor systems and roof sytems that ive repaired or had to beef up doing major additions and structural alterations too would boggle your mind.. its scary how thing use to be framed.. and people wonder why they have a sag in their ceiling
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Old 04-26-2013, 09:13 PM   #13
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32" cantilever BEAM Double 2x10 on a 19' run??


This may be a stupid question, but why did you do this? Move one of the posts to the end already. Did you put footers under this slab and then decide to increase the size of the deck? Never mind, now I see. The post was falling in the middle of the window. Oops. I would move the post to the end, and evenly space the posts. Sorry.
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Last edited by jagans; 04-26-2013 at 09:16 PM.
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Old 04-27-2013, 08:28 AM   #14
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32" cantilever BEAM Double 2x10 on a 19' run??


you will also need better flashing on the wall where the deck lands on it. the flashing needs to go onto the top of the siding as it comes up to the deck and meets the deck from underneath to direct water from behind the deck and onto the outer portion of the siding to keep the water out from behind the siding.
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Old 04-27-2013, 09:30 AM   #15
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32" cantilever BEAM Double 2x10 on a 19' run??


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you will also need better flashing on the wall where the deck lands on it. the flashing needs to go onto the top of the siding as it comes up to the deck and meets the deck from underneath to direct water from behind the deck and onto the outer portion of the siding to keep the water out from behind the siding.
The flashing needs to go behind the Tyvec, behind the siding, in shingled fashion. Maybe thats what you meant?

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