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Old 05-13-2013, 03:08 PM   #31
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


[QUOTE=madmilitia;1178495]ok ok i'm new, first things first.

this second support beam that i'm going to stand up, i want to put it as close as i can to the excisting one, because i'm still going to siste the 2x12s to the old 2x6 joists for strength.

so i'm hearing (2)2x10's for the new support beam, keep in mind if i can dig the hole right taht new support beam is going to be like 2-3 inches from the excisting support, <<< doing that do i really need to use 2x10's

second are you saying that i CAN dig holes under the old beam and fill in concreate and hammer in more 4x4's?[/QUOTE] That's not a problem at all.

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Old 05-13-2013, 03:15 PM   #32
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


If your plan is something like the attached sketch, your tributary area of loading on the double beam will be approx 8'x6'6", = 52 sq ft.

Assuming live load 40 psf (?) and dead load 10 psf, total load on beam would be around 2600lbs.

Maximum bending moment will be 31200lb in.

For two 2x6s (probably 3 x 5 1/2) this bending moment will produce a bending stress in the timber of > 2000lbs/sq.in.

Most softwoods are maybe in the range 800 - 1200psi, so your beams would be overstressed. You definitely need to consider at least a third beam.


PS got distracted before I pressed the 'submit' button and missed everyone's latest posts. Yes, just try and stick a central post under the double beam and it'll work.
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help-mini-scan1411.jpg  

Last edited by tony.g; 05-13-2013 at 03:21 PM. Reason: missed other posts
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Old 05-13-2013, 03:17 PM   #33
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


I have difficulty in answering some written questions...... sorry. I'm a visual person, and I usually need some fairly detailed and accurate plans to fully grasp some concepts. Can you get us something like Tony did?
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Old 05-13-2013, 03:53 PM   #34
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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I have difficulty in answering some written questions...... sorry. I'm a visual person, and I usually need some fairly detailed and accurate plans to fully grasp some concepts. Can you get us something like Tony did?

yeah sorry tonight when i get home i'll measure and draw out a better picture for you guys.
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Old 05-13-2013, 03:55 PM   #35
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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Originally Posted by tony.g View Post
If your plan is something like the attached sketch, your tributary area of loading on the double beam will be approx 8'x6'6", = 52 sq ft.

Assuming live load 40 psf (?) and dead load 10 psf, total load on beam would be around 2600lbs.

Maximum bending moment will be 31200lb in.

For two 2x6s (probably 3 x 5 1/2) this bending moment will produce a bending stress in the timber of > 2000lbs/sq.in.

Most softwoods are maybe in the range 800 - 1200psi, so your beams would be overstressed. You definitely need to consider at least a third beam.


PS got distracted before I pressed the 'submit' button and missed everyone's latest posts. Yes, just try and stick a central post under the double beam and it'll work.

wow thanks for the math, ok so i need to build a new support beam, cause this addtion is going to take on an L shape. so that 2 of the 4 sides are surronded by decking.

and i belive my newly added support beam will be about 16 feet long. i'll try to draw a picture for you guys.

are there any online cad programs?
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Old 05-13-2013, 04:04 PM   #36
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


this is fairly simple and straight forward http://www.sketchup.com/intl/en/download/gsu.html

there are videos on youtube and there site for how do use it, and it's FREE and will do 3d
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Old 05-13-2013, 04:08 PM   #37
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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this is fairly simple and straight forward http://www.sketchup.com/intl/en/download/gsu.html

there are videos on youtube and there site for how do use it, and it's FREE and will do 3d
You can hardly do any better than this. And it is easy to learn... besides being fun!
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Old 05-13-2013, 04:10 PM   #38
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


ok givwe me abit an i'll setch up the plan
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Old 05-13-2013, 04:18 PM   #39
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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ok givwe me abit an i'll setch up the plan
You'll never regret getting, and learning SketchUp. It will reward you a thousand times over in satisfaction and convenience.
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Old 05-14-2013, 11:25 AM   #40
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


ok ran into a problem, the place i need to dig down to set another support beam next to the support beam that is there already is non compaced dirt.
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Old 05-14-2013, 12:01 PM   #41
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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ok ran into a problem, the place i need to dig down to set another support beam next to the support beam that is there already is non compaced dirt.
If I read this literally. I'm confused.
Post- vertical
Beam- horizontal
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Old 05-14-2013, 12:09 PM   #42
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


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ok ran into a problem, the place i need to dig down to set another support beam next to the support beam that is there already is non compaced dirt.
footings that bear structural load must be down to at least your frost protection depth (12' Minimum, verify with your building department), and to undisturbed virgin material. if the soil is disturbed you need to go deeper, if not you'll probably have compaction/settling issues
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Old 05-14-2013, 12:18 PM   #43
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


ok so i found that i can't dig in a main suuport for my addtion because the ground is unsettled soil.

i also took measurements and drew a better picture.

so i have to use the already there support beam for this addition, i assume that means i'll have to reenforce it but heres a pic let me know what you think

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Old 05-14-2013, 12:25 PM   #44
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help





http://www.flickr.com/photos/9569496...in/photostream
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Old 05-14-2013, 12:27 PM   #45
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extending my deck. sistering a 2x12 to a 2x6 joist to gain riase need help


Don't anyone give me grief on this (!) but would your code allow you to bolt additional 2x6s each side of the existing beam?
Granted the beam is not then supported full-width but it would beef up the existing arrangement.
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