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Discussion Starter · #1 ·
We have basically rebuilt this house to the point of replacing exterior walls and floor joists. I'm saving the tongue and groove bead board ceiling. However, the original ceiling joists are 2 x 4's, and termite damaged to boot, probably on 24" centers (don't remember exactly).

We would like to support the ceiling because we are going to have to put in duct work and wiring & insulation in the attic and would rather not risk falling through!

The plan is to add 2 x 6's or, more likely double 2 x 6's on the underside or room side of the ceiling resulting in an open beam look. Ceilings are 9 1/2' tall. The interior of original house is about 15' x 35' with a 6-foot deep porch.

Question: Can we use a 15 foot span for the 2 x 6's? Do we need a center bean instead of running joists all the way across? What can our spacing be if we do double 2 x 6's instead of a single 2 x 6?
 

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We need one of our resident engineers to see this--so --Bump!!
 

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Discussion Starter · #3 ·
yes, thanks so much, we do need engineering help! To start with, how much stronger are two 2 x 6's paired together than just a single one used as a support? That might be a good thing to know.
How would the spacing differ, say 16" centers vs (what?)
 

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If you're pulling a permit and plan to do this prescriptively (according to code) without hiring an engineer, then the simple answer is: NO.

The maximum allowable span depends on the size, grade and species of lumber as well as the expected load. For a 15' span, you would need to look into 2x8s as a starting point. Even then, only certain grades and species of lumber will work. When you start talking about doubling up the joists, I believe you step outside the reach of the code and step into engineering land. Have a look at the following tables:

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_5_par015.htm?bu2=undefined

This all assumes that the area you live in has an enforceable building code. Lots of variables...
 

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Discussion Starter · #6 ·
Here is a chart with different spans hopefully it will help.
http://www.awc.org/technical/spantables/tutorial.php

Thanks, very nice chart. What does the SS stand for? I can see I need to go up to perhaps a 2 x 10.
The chart is for attics with fixed stairs and sleeping area. This attic is just for the duct work and wiring. No one will be up there except to install various things like the insulation etc. Of course it wouldn't hurt to over do this a bit.
 

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Discussion Starter · #7 ·
If you're pulling a permit and plan to do this prescriptively (according to code) without hiring an engineer, then the simple answer is: NO.

The maximum allowable span depends on the size, grade and species of lumber as well as the expected load. For a 15' span, you would need to look into 2x8s as a starting point. Even then, only certain grades and species of lumber will work. When you start talking about doubling up the joists, I believe you step outside the reach of the code and step into engineering land. Have a look at the following tables:

http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_5_par015.htm?bu2=undefined

This all assumes that the area you live in has an enforceable building code. Lots of variables...
We have pulled permits. The house is in New Orleans, :jester: west bank, Algiers. I can see the need for something larger than a 2 x 6. Thanks so much. I assume we're using Souther Pine, treated. I will have to do more local research but you've given me some very good information. Thanks.
 

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SS stand for?
SS stands for Select Structural which is the highest grade of lumber, also the most expensive. Normally most builders would use either #2 or #3 except where SS only works.

http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_sec002.htm

These span tables start off with unhabitable attics without storage and go to attics accessed by fixed stairs. if you are attaching gypsum wall board as your ceiling you'll want to select the L/240 deflection limits.

Find your span (between supporting walls/beams), the load you want your attic floor/ceiling joists to support, L/240 deflection limits and size your joists based upon the grade and species of lumber to be used.

hope this helps. Good luck! :thumbsup:
 

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I assume we're using Souther Pine, treated.

I missed this post. Why are you planning on using treated wood? I would not put "chemicals" into your home when not required. Depending on what the wood was treated with you could have a reaction between the wood and metal ductwork (dissimilar metals). Plus you can expect to have a lot of shrinkage as treated wood is normally "wet" and will dry out over time.
 

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Discussion Starter · #10 ·
I assume we're using Souther Pine, treated.

I missed this post. Why are you planning on using treated wood? I would not put "chemicals" into your home when not required. Depending on what the wood was treated with you could have a reaction between the wood and metal ductwork (dissimilar metals). Plus you can expect to have a lot of shrinkage as treated wood is normally "wet" and will dry out over time.
Treated wood came up because the house was nearly distorted by termites but you are absolutely right, the treated wood adds chemicals to the house and also shrinks a lot. We will have to reconsider. Thanks so much for this input!
 

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Discussion Starter · #12 ·
+1 no treated wood indoors. Have you already treated the foundation to prevent the return of termites? The Formosans down here are brutal.

LSU has a good article here: http://www.lsuagcenter.com/en/famil...ermite+Protection/Pier++Beam+Construction.htm

I'm assuming your shotgun is on pier and beam, and being as old as it is, doesn't have metal caps. Good luck.
I'll check out the article. It was a bubble construction originally. It is on piers about 18" off the ground.
 

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Discussion Starter · #13 ·
I wanted to post a couple of photos of the ceiling problem and was trying to follow the instructions Cricket posted but messed up somewhere along the way. Now my paperclip icon has a red "X" through it and I am dead in the water.

It is an unusual situation that would be easier to understand with pics.

I'll try another time. Thanks to all for help.
 

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If you look below the "Submit Reply" box you will see "Additional Options" there you will see "Manage Attachments" click on that and load your photos from there. Just follow the instructions.
 

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Discussion Starter · #15 ·
The situation we're dealing with is rather odd I guess. The ceiling is the original bead board tongue and groove. It is the only remaining feature of the old house. Here are some photos of what we're looking at. I thought supporting this sturdy (where it is not termite damaged) ceiling from below (in the room) would allow us to keep it. The ceiling is 9 1/2'.
 

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