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Huggins90 12-27-2012 12:30 AM

Load bearing wall removal question...
 
2 Attachment(s)
So here's the situation. I am removing a load bearing wall where 2x8 ceiling joists overlap.
There was previously a flat roof on these joists so they are decked with plywood/osb. The plan is to provide support with temporary walls on either side of the wall to be removed, remove the wall, cut the joists and the plywood down the length of the wall to slide the (city approved) doubled 2x12 header/beam to make the beam flush with joists.

Then attach with joist hangers. My first question is, anything wrong with this plan? The span is 17'. There is no second story, single gable roof, pierling over two load bearing walls at apprx. the midpoint of the rafter span, no additional weight that the joists will be supporting other than the weight of themselves and insulation I guess. :)
My second question is, do I need to be worried about outward pressure on the exterior walls? If I cut through the joists, isn't this what is keeping the roof weight from pushing the walls outward? If so, what would you suggest doing to still be able to get a flush header? There are no rafter or collar ties or anything similar. Maybe add some of those before hand?

Attached are two pics, I can post more if need be.

Thanks!

Missouri Bound 12-27-2012 01:25 AM

I hate to ask this, but do you need to keep the beam flush with the rafters? If you could allow the beam to drop down the 4" would it be an issue? When you cut through the plywood you are losing everything tying the walls together. A few pictures, maybe from the outside may help a bit. I would try to tie it all together, at least at every other wall stud.....before you start cutting. Have you had an engineer look at it? Maybe a drawing would help visualize as well.

mae-ling 12-27-2012 02:11 AM

You say these were rafters? Is there now a roof over this? You could run 2x4" underneath the beam from side to side say every 8' to temporarily tie walls together, Say use 16' 2x4's and overlap in center. Nail thenm to the sides of your outside wall studs and to the side of your temporary wall studs to keep them up in the center.

rossfingal 12-27-2012 06:32 AM

I don't know your location; so, I don't know the potential "snow load"....
17 ft. span? -
Double 2 X 12's?
That would not be acceptable, around here.
Minimum would be double, lam-beams; probably, bolted together.

No matter what you do - I would brace the walls and tie them together -
(As "mae-ling" suggests)

Might be a good idea to have a structural engineer look at it.

Good luck!

rossfingal

Huggins90 12-27-2012 10:34 PM

Missouri Bound;

Yes, if at all possible I would like to keep it a flush beam. However, everything is negotiable... I would just like it to look as clean as possible. What do you mean by tie it all together?

Mae-ling: yes these were the rafters for a flat roof, there is now a single gable roof over this, the 2x8s are acting as ceiling joists now with plywood decking. So you are saying if you ran 16 footers from one exterior wall to the other doubled in the middle then just nailed or screwed together? then attach to temporary walls for support in the center. Sound like a plan. Every other stud work? or what would you recommend? Thanks!

rossfingal: Its actually more like 15 foot. there will be an extra wall in there giving support. But yes, the city actually told me to use 2 2x10s. So I opted for 2x12s. There is not much snow down here in southern Oklahoma. Also they are just ceiling joists now, not holding up much weight. Thanks for the input!

GBrackins 12-28-2012 12:50 AM

what is the distance from one end of the "ceiling joist" to the opposite end? (total span of ceiling joists), is there any storage or access between the old "flat roof" and newer gable roof? (in other words would have to access this area to make repairs or perform maintenance?)

something to remember, just because someone at the city said you can doesn't mean you can .... they may know, and then again they may be guessing, after all it's not their place

mae-ling 12-28-2012 01:09 AM

I'd only go about every 8' with the temporary side to side tie together.

Gary in WA 12-28-2012 01:09 AM

So now you have a gable roof, are the ceiling joists now acting as rafter-ties; you may need a better connection at the rafter/joist or header/joists to maintain rafter resistance unless enough of the plywood floor is acting as a "floor" diaphragm with the rafters sitting on it. Depends on how long the section you are removing is, compared to the remainder. Will you be using "shear" hangers on the b.u. beam?

Gary

747 12-28-2012 01:28 AM

Your going to need the proper calculation for a lvl beam. I would highly recommend getting a structural engineer.

carpdad 12-28-2012 10:35 AM

Town permit office generally tries to encourage building, so it may give you ok based on the minimum allowed with "acceptable" deflection built in. But this is usually not acceptable to you and me. I would go with LVL and consult the LVL maker's own engineering department. So long as you have made commitment to buy, its engineering department will even fax you the spec sheet that you can take to your permit office. Specify a "dead load".
Before you do this, you need little more info on your current roof. I am not sure if your roof rafters by themselves are adequate to resist bending over time. If you need supports, your girder equations may be different.
2x12 girder may be easier to make, but for your span, I would recheck the numbers by searching for girder tables and/or consulting an engineer. Your town affiliated engineer may help you at a discount. Sometimes, crown is built in intentionally to account for future settling. Find the driest lumber and check for moisture content yourself.
Visually check that ends of the girder are supported with equal width all the way to the foundation, and no gap in the support contacts, and foundation around the support contacts is in good condition without cracks, fracture, etc.
At finehomebuilding forum site, there is similar discussion on girder/beam requirements.

Gary in WA 12-28-2012 11:20 PM

We can answer your questions here, on this forum... don't leave. As you are worried about the spreading of the rafters, not the beam size to be allowed per local AHJ, give us a picture of the rafter/floor connection, please. Minimum code requires varying numbers of fasteners at the rafter/joist connection due to the varying stresses produced there, last chart at the bottom; http://publicecodes.cyberregs.com/ic...002_par023.htm

Your application may be similar to this; pp.11- http://www.awc.org/helpoutreach/ecou...seV09-2007.pdf

Hence, the picture, please.

Gary

loftezy 12-31-2012 12:17 PM

You are right, you will need something to keep the walls from spreading. The joist hangers that you are planning to install are great for holding the joists up, but they won't do anything to keep the walls in.

You'll need something like this:

http://www.strongtie.com/products/co...S-HST-LSTA.asp

However, your flush beam design may make it difficult to use these straps. The most basic installation method would be on the bottom of the joists where they meet flush with your new beam. However, unless you are good with drywall, you might see the bulge on your ceiling when the drywall is done. If it were me, I would try to find straps that allow you to go over the new beam and then attach to the SIDE of the 2x8 joists. This means that the strap would have to twist on both sides of the beam so that it would be flush to the side of the 2x8's.

I suggest that you call Simpson to see if they have a connector that works in your situation. Also, you'll probably need to check with your engineer to see how many and what size straps you'll need.

Huggins90 01-09-2013 11:41 PM

4 Attachment(s)
Ok, thanks for the help so far guys.

Update,

Here are some more pics, now I would like advice on how you would handle the entire wall removal, beam size, beam material, and whether you would do flush beam or just drop it down. Also, from the pics, you can see there are vertical supports running from the ridge of the roof, down onto a flat 2x6 on the attic floor across the joists right on the wall I am removing. Do these actually carry weight? How can I remove and cut what is under it if it does? Thanks so much!

Huggins90 01-09-2013 11:46 PM

4 Attachment(s)
Attic views...

mae-ling 01-10-2013 12:17 AM

A dropped beam is much much easier, Having said that there are times when a flush beam will visually be better.


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