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Old 04-22-2011, 09:17 PM   #1
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LVL Beam Sizing


I am replacing a 16 foot load bearing wall with an LVL beam in my single story ranch. The wall separates the kitchen from the LR. We are going with an open floor plan. Above the wall is the attic. I am going to leave the attic floor joists in place (2x6 not cutting them) and install the beam above the joists (in the attic itself). The joists will be supported from the beam up above with Simpson Strong-Tie twist straps (TS18).
The length of the joists on either side of the wall are 11' and 17.5 feet. If I use 20# per sq. ft. attic floor loading (DL & LL), I calculate that the beam has to support a total of 4,560 lbs. What size beam do I need? My local building supply store says two 1-3/4 inch x 11 7/8 inch Ridgelam LVLs screwed together (side by side) will do the job.


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Old 04-22-2011, 10:10 PM   #2
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LVL Beam Sizing


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I am replacing a 16 foot load bearing wall with an LVL beam in my single story ranch. The wall separates the kitchen from the LR. We are going with an open floor plan. Above the wall is the attic. I am going to leave the attic floor joists in place (2x6 not cutting them) and install the beam above the joists (in the attic itself). The joists will be supported from the beam up above with Simpson Strong-Tie twist straps (TS18).
The length of the joists on either side of the wall are 11' and 17.5 feet. If I use 20# per sq. ft. attic floor loading (DL & LL), I calculate that the beam has to support a total of 4,560 lbs. What size beam do I need? My local building supply store says two 1-3/4 inch x 11 7/8 inch Ridgelam LVLs screwed together (side by side) will do the job.
I don't think this plan makes structural sense. If you don't want the beam below the ceiling joists, cut the joists and put the support in the same plane.
Ron

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Old 04-23-2011, 09:04 AM   #3
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LVL Beam Sizing


Yes there are three options here. I can put the beam under the joists, flush with the joists or above the joists. The local building inspector (I've been there three times) mentioned this design (above the joists). In this way the joists stay intact and we won't see any cracking in the ceiling sheet rock a year from now after everything settles. The section of attic above is essentially unused. However I am being open minded to the design before any work begins.
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Old 04-23-2011, 09:35 AM   #4
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LVL Beam Sizing


There are a few engineers that post here, I'm sure they'll offer a more learned opinion.
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Old 04-23-2011, 12:04 PM   #5
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Your plan is feasible, however I do not recommend use of twist straps to support joists. Joist hangers are more positive connectors, and of course Simpson makes a line of them, one of which would certainly meet your needs. You would simply need to cut the joists, install the beam, install the hangers, and nail the joist ends into the hangers. Just make sure you use the Simpson specified nails, and use all of them.

As for sizing the beam, if your supplier is willing to certify the beam for your application, and the building inspector will accept their certification, that seems like the way to go. Unless you have a very unusual building inspector, they are not likely to accept a design from an on line chat room. You could always hire an engineer to size the beam, but if the supplier will size it for you, why spend the extra money?

You need to carefully design the supports for the beam. I did a similar project between my kitchen and dining room, and I used tripled wood 2x4 studs to support each side of the beam (I used a steel beam). You have probably discussed this with your inspector; depending on the length, you may be able to get by with doubled studs, ask the inspector. The studs need to be positively connected to a main beam in the basement, or they need to be supported on individual footers. You have probably worked all this out, but you need to show all of the connections on the plan, at least in my town you do.
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Old 04-23-2011, 09:52 PM   #6
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yes I will use tripled wood 2x4 studs to support each side of the beam (although I did not think of using a steel beam). I guess I'm going to have to rethink the joist support system. Several people are recommending that I cut the joists and mount the beam flush using joist hangars as opposed to supporting the joists from the beam mounted above.
As far as the two wood stud supports at either end of the beam each will go through to the basement (one story). One will sit on a concrete foundation wall which is supported by a footing; the other side will sit on the 3 inch concrete floor. I was told by inspections that I didn't need a footing for it. What can I put on the end of the triple stud to distribute the load (2,330 lbs) over a larger area?

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Old 04-23-2011, 09:59 PM   #7
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Originally Posted by rjmcg View Post
yes I will use tripled wood 2x4 studs to support each side of the beam (although I did not think of using a steel beam). I guess I'm going to have to rethink the joist support system. Several people are recommending that I cut the joists and mount the beam flush using joist hangars as opposed to supporting the joists from the beam mounted above.
As far as the two wood stud supports at either end of the beam each will go through to the basement (one story). One will sit on a concrete foundation wall which is supported by a footing; the other side will sit on the 3 inch concrete floor. I was told by inspections that I didn't need a footing for it. What can I put on the end of the triple stud to distribute the load (2,330 lbs) over a larger area?
The jack studs should be connected to the bottom plate of the wall.
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Old 04-24-2011, 07:54 AM   #8
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There is only a wall with bottom plate on one end; the jack stud on other end of the beam falls where there isn't a wall. That jack stud will have to be mounted directly on the 3.5 inch concrete floor. I could dig a footing but that may be overkill as I think that the floor can handle 3000 lbs/sq inch. I will have 2330 lbs spread over 12 square inches.

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Old 04-24-2011, 07:58 AM   #9
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There is only a wall with bottom plate on one end; the jack stud on other end of the beam falls where there isn't a wall. That jack stud will have to be mounted directly on the 3.5 inch concrete floor.
You do not want the wood directly on the concrete. Look into the Simpson hardware catalog for a standoff support.
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Old 04-24-2011, 09:22 AM   #10
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Couple of comments.

1. Although the concrete in your basement may be rated at 3000 psi, that does NOT mean you can put a heavy load on it. The limiting factor is diagonal shear of the concrete, which is a function of the thickness of the floor and the area of load. Normally the column (the two or three studs you bring to the basement) are supported on a separate footing, designed to prevent frost heave and concrete cracking. As an alternative, the load can be spread over a larger area by using a steel plate. In either case, it is important that the column be physically anchored to the foundation, using either J bolts, epoxied anchors, or equivalent anchors. Anchoring the column reduces the chance of column movement during an earthquake or high wind event. The same goes for the other column, which must be anchored either to the sill beam, or directly pinned to the concrete wall.

2. You do not want wooden columns to rest directly on concrete. The wicking of moisture will rot the columns very quickly. The standard approach is to install a galvanized steel standoff bracket to support the column, Simpson makes a line of them, as do other manufacturers.

3. There is no need to install a special plate on top of the column, as long as the two or three studs are flat on top, you can attach the column to the beam using either a hanger (Simpson and others make them), or lag screws. Personally I prefer the galvanized steel column connectors. The exact bracket depends on the geometry of the connection. The simplest technique is to install the beam directly on top of the column using the appropriate bracket. As in the bottom of the column, you want a positive connection here to prevent separation during an earthquake or high wind event. The brackets cost under $20, and will provide a positive connection well worth the investment.

4. You may want to consider a steel beam, the cost is competitive with LVL, and they are not as deep. Connections are somewhat more complex with steel, but not beyond DIY. I installed a steel S beam for my 11'6" kitchen header, it worked out very nicely, and saved me approximately 4 inches of headroom versus conventional lumber, which I liked.
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Old 04-24-2011, 05:14 PM   #11
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Will I have to open up the walls (cutting the existing sheet rock) from ceiling to floor in order to get the wooden columns installed? (I can't visualize any other way).
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Old 04-24-2011, 05:25 PM   #12
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You probably do have to open up the wall, I certainly had to. You also have to cut an opening in the floor to slide the column through. All part of the fun of installing a header.
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Old 04-24-2011, 05:41 PM   #13
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thanks. If I have to open up the floor to slide the column through is the floor now weakened at that point? Do I now have to somehow support the floor around the new column or is that unnecessary?
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Old 04-24-2011, 05:52 PM   #14
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Your floor typically has a subfloor (plywood) and hardwood or something similar. There is usually no need to strengthen the floor, unless you happen to have it supported on poor material like chipboard, in which case you might need to add an extra joist where the floor overhangs. You can always add a wooden or metal bracket attached to the column to support the floor adjacent to the column if it is necessary.
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Old 04-24-2011, 06:11 PM   #15
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thanks. If I have to open up the floor to slide the column through is the floor now weakened at that point? Do I now have to somehow support the floor around the new column or is that unnecessary?
I'm confused. You said the support for this header was going to rest on concrete. Now you mention a plywood floor. If this renovation is happening on the first floor and this is a load bearing wall, there will be a main support beam under this, and running parallel to the new load bearing beam. If that's the case, the jack studs would set on the botton plate over the subfloor. You would then fill the space under the subfloor with solid blocking above the main beam below to carry the load.
There would be no reason to carry the load down to the concrete floor.
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