[Huggins90]

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]

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]

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]

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]

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]

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]

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

 

[Gary in WA]

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]

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

 

[carpdad]

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]

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/icod/irc/2009/icod_irc_2009_8_sec002_par023.htm

Your application may be similar to this; pp.11- http://www.awc.org/helpoutreach/ecourses/MAT108/MAT108eCourseV09-2007.pdf

Hence, the picture, please.

Gary

 

[Underdog]

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/connectors/HRS-ST-PS-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]

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]

Attic views...

 

[mae-ling]

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

 

[Huggins90]

Also, Forgot to mention the beam will be 15ft. unsupported it will be more like 17 ft. total length, but 15 of it will be unsupported. What size? No real snow load, southern oklahoma.

 

[Gary in WA]

Because some of your roof load is supported by the frame walls above, resting on the flat roof, you have a special situation that may require a structural engineer. You have more than ceiling loads. The SE would give the fastening requirements of the new roof added above the flat one, especially at the joist/rafter connection for shear thrusts as well as uplift resistance. And, the paper trail would appease the local AHJ (with new permit for structural changes), and help with your HO Insurance carrier, if a future claim from this work. He/she would take liability for the beam, bearing, fastening, shear, etc.

Gary

 

[Huggins90]

Update

So I have engineers drawing up a plan. However, the first thing they said to me was..."I'm not sure you're going to be able to remove that. I just don't see how." Umm...you are a structural engineer are you not? Problem solve! So eventually he suggested some beam options claiming it needed to be steel, which I disagree with. Then he said, well yea we could probably do LVL. So long story short, I felt like I had to exert extra effort just to get him to think outside the box and give me some options. Needless to say, I did some thinking on my own after he left.

I drew up a few figures on what my situation looks like. Look at previous pictures to see the situation in person. There is the one wall in the center of the room, the wall in question. I have built two walls on either side approximately cutting the room into fourths. From one new wall to the other is 15'. The ceiling joists are 2x8s running from one exterior wall to the middle wall doubling over in the middle. Instead of running a beam perpendicular and trying to fasten joists to it, could you not run new 16' 2x8s sistered onto each joist from one new wall to the other? The only problem I see with this is a bit of a sag in the middle due to the roofers framing down onto the middle wall making it load bearing (duh). But as far as just holding up the ceiling weight, 2x8s can span 15' yes? So then as far as taking care of the sag, could you run a beam alongside the middle of the roof supports coming down onto the wall, maybe a 2x12 or 2x14 on each side of the 2x6 supports sadwiching them together with 2x6 in between and lag bolt them so that the beam is carrying most, if not all, of the roof support weight, thereby eliminating the extra load on the joists enabling them to be carrying ONLY the ceiling weight, (no storage on top). Seems like its pretty simple to me. But, I am no engineer. So give me your thoughts about this system and if it won't work. I don't want to do it wrong, I just want to do it without steel, and without hiring it all done. Thanks so much. This site is awesome.

-Huggins90

P.S. In first drawing, highlighted wall is the wall to be removed, green dotted lines represent pier and beam locations or foundation walls. If you need me to explain anything else let me know. Anxious to here everyone's thoughts.