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Old 12-18-2011, 10:42 AM   #1
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12' span glulam beam?


i have a bearing wall in my basement that i would like to remove to expand our family room. the span from where i want to end my bearing wall to the foundation is 11'-8". My plan is to temporarily shore up my floor joists (floor joist span is 25' [i-joists]). tear down the old bearing wall and replace with a glulam, then remove the temporary shoring wall. i just need some assistance with the sizing of my glulam. any thoughts?

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Old 12-18-2011, 10:50 AM   #2
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12' span glulam beam?


yes you do need help, there are several things to consider when sizing up such a beam. you need to consult an engineer, they will draw up a sketch and spec the depth and thickness of the beam along with the post that will support the floor. you will also have to jack hammer up the slab where the post will sit so to put a footing in the ground to support the additional weight

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Old 12-18-2011, 10:51 AM   #3
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12' span glulam beam?


Yep, get a structural engineer to size it and any needed posts, connections. It will be safe and the building dept will want to see an approved plan from someone licensed.
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Old 12-18-2011, 12:18 PM   #4
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12' span glulam beam?


I rarely use engineers unless absolutely necessary. I used to create spreadsheets specific for each beam I designed, but then I found the ConstructionCalc tools. Their ProBeam spreadsheet is pretty simple to use, and it already contains all of timber profiles and other constants. It lets you enter a number of different type loads, live/dead, distributed and point, and it gives you multiple choices for material options that might work best in your situation. I've not found a situation for which the program wouldn't work. You can checkout their demo at: http://www.constructioncalc.com/blog/software-demos/. It's inexpensive, and accepted at least with building departments that I've worked with. Also, as others have stated, you will need to pour footings at the support points for the beam, but their size is easy to calculate based on the load bearing capacity of your soil. You will also have to include appropriate vertical support and connections in the walls at the ends of the beam.
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Old 12-18-2011, 01:26 PM   #5
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12' span glulam beam?


Dave,

How does one find out: "...the load bearing capacity of your soil."?
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Old 12-18-2011, 02:00 PM   #6
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12' span glulam beam?


Quote:
Originally Posted by bob22 View Post
Dave,

How does one find out: "...the load bearing capacity of your soil."?
Actually in California, most cities already have the information for how much your soil is capable of holding per PSI in a given neighborhood. Not all cities and not all neighborhoods in all cities of course but many do.
Most do in Orange and LA Counties, so I have found.

Unlike Dave54 I have to use licensed engineers most of the time for the remodels that I design for a client. Most are 2 stories and are in a seismic D sub 0,1, or 2 area so I am only allowed to do the prescriptive design for a single story home.

The hosed thing is that 50% of the time I have specified that an engineered product be used, be it an LVL or even "I" joists the cities then want full on engineering for the whole house.
That sucks, but I understand that they want to limit their liability any way they can.

Andy.

Last edited by AndyGump; 12-18-2011 at 08:13 PM.
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Old 12-18-2011, 03:17 PM   #7
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12' span glulam beam?


I work for a heavy civil contractor and do have a lot of connections with structural engineers, I guess I could give the a call. Some of you have mentioned chipping out my floor to build footings, since this is a bearing wall, the home builder did put a footing under the floor slab in this location. Do you think I would need an even bigger footing? Or would the existing one be sufficient for the support post point loads. Also do you think a glulam is the way to go for this 12' span or are there other alternatives that may be cheaper or better?
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Old 12-18-2011, 04:54 PM   #8
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12' span glulam beam?


ive installed 14' 2 ply 16" lvl's for similar situations but it can vary on the situation.. this was supporting another floor plus a roof load and was engineer spec'd... memory serves correct installing it was how i spent my new years eve afternoon two years ago
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Old 12-18-2011, 07:06 PM   #9
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12' span glulam beam?


What size of footing is under the slab? Do you have the original plans.
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Old 12-18-2011, 07:20 PM   #10
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12' span glulam beam?


Sizing a beam for a situation such as yours has been discussed repeatedly on this forum over the past few years, you can do a search and find at least 20 threads. A lot of people think that sizing a beam is a pretty routine thing, doesn't require any engineering, or if it does you can get the answers out of a table or at worst you can purchase a computer program to do it for you. And much of the time, that is correct. About 10 percent of the time, there is something unusual about the situation, and it may be very difficult to tell if you have such a case, unless you are trained.

I am not one who advocates that individuals untrained in structural engineering buy a piece of software and put trust in it, too easy to miss something. But to each their own.

I suggest that you consider a steel beam as an alternate to a glulam or an LVL, in some cases the reduction in required depth offers advantages, and the cost differential may be minimal. You do have to design the connections carefully, mating wood to steel can be a little tricky.

I do not recommend sizing a beam over the internet. The problem is that those who are capable of doing it should not do so, because they may inadvertently accept liability for improper design, or improper installation. Those who are not competent to design the beam are of course free to offer whatever advice they choose, since they are not considered expert, and likely would have no liability for erroneous recommendations.

This of course leaves you in an odd position; how are you going to tell from an internet chat forum whose advice to take? If you are trying to save money on design, my suggestion is to go to a lumber yard that sells glulams or LVL's, give them a carefully drawn diagram of your house, and ask them to prepare a stamped design as part of the purchase price. Some yards will do just that, which saves you a few bucks on design, and gives you a design document you can take to the code enforcement official. You may be able to get similar service from a steel supplier.
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Old 12-18-2011, 07:25 PM   #11
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12' span glulam beam?


If you go to the website of the company that makes the beam, they have a book with span tables. Just look up your application and it will tell you the size of the beam. It will be pretty big, I think.

Bigger issue is foundation. Can whatever post is going to hold up the other end be supported.
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Old 12-18-2011, 09:35 PM   #12
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12' span glulam beam?


With regard to soil bearing capacity, the local building department will have the specific answer, but most seem to adopt some version of the UBC standard, which states the following:

Crystalline bedrock = 12,000psf
Sedimentary and foliated rock = 4,00psf
Sandy gravel and/or gravel = 3,000psf
Sand, silty sand, clayey sand, silty gravel and clayey gravel = 2,000psf
Clay, sandy clay, silty clay, clayey silt, silt, and sandy silt = 1,500psf

I work mostly in clay, so I'm used to large spread footings for everything.

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