LVL beam vs I beam

[B.L.]

i am designing my house and i have a room that is 29' x 41.5' with 2 different ceiling heights.  i have 4 - 24" lvl's to carry the load over the 29' span.  in the icc joist table i used live load 20 psf and dead load 10 psf to calculate joist sizes.  there is also  3 - 24" lvl's that t into this beam about half way that spans 21.5' also supporting joists.  instead of using engineered lumber, would it be more cost effective to use a single I beam for the main beam and the tributary.  the reason this became an issue is i have another room with a 34' span and a lvl beam will not work because of deflection.  i have redesigned the lvl support beams as to where it will work but i am increasing the amount of material as to where the cost is getting high.   I have all the formulas for calculating the size of I beam needed but i would like a little reassurance from some other professionals.  it seems to me that a single I beam is more cost effective than all this lumber.  The room is 34' x 25'8" and the way it is designed the beam should span the 34'.  any information on the beam size would be appreciated.  

thanks

 

[Holzhacker]

Hopefully this doesn't sound too rude, but if you are building rooms that size you should be hiring a Structural Engineer to do your load calcs. Those rooms are too big for a layman to read books and design it himself. So unless you are a licensed SE, hire one. No matter how smart you think you are. Of course if you are building rooms that big you should have sufficient money to hire an SE. If you don't have the money, then you probably shouldn't be bigger that monstrosity.
I've been in the trades my whole life and have no issue designing or spec'ing loads or structural components for 'normal' houses. I've dealt with enough jobs, engineers and architects to know what will and what won't work. There are however jobs where I leave the Spec work to a Pro. With spans that big I would not recommend just looking at load tables and saying 'oh that works per the load table'. I've been on too many jobs where, yes it works per the load table. Unfortunately the idiot contractor and architect didn't take life into account. Even if it is 'safe' people don't like walking on a floor that they can feel moving. When LVL's first started getting wide usage here, noticeable bounce was a real issue. The installs were compliant but nobody liked them.
A couple things to consider:
- A crew can probably move LVL's no problem. You may need a crane or hydraulic rollers for the I beam though. i.e. additional cost
- An I beam is unlikely to cost less, at least around here
- You also need to consider the deflection values for your finished flooring products if its going to be something besides carpet
- substrate needs to be properly glued and screwed in these cases, not just nailed down
Gotta go

 

[peter halle]

I will have to agree with Markus about getting an engineer involved.  I would doubt that you ever would get your plans approved by the local code officials without an engineer's stamp or an architects's stamp anyway.  And it is likely that your architect would be using an engineer to review to boot.  Better to get one on board early in the process and determine if design changes would be necessary due to exorbitant requirements or potential costs and potentially save some serious redesign time.

Just my tights.

Peter

 

[Vindingo]

Hire an architect and an engineer.

The space is too big to just use charts.  You make no mention of roof pitch, intended use, geographical location... so many other things to take into account.  

No person qualified to confirm your calculations will do so over the internet, or be willing to based on what little information you have provided.

Hire an architect and an engineer.

 

[B.L.]

i apologize for not being a little more thorough with my description.  i did go to college for arch. engineering though it has been a long time and i am not in that field as a career either.  i have drawn the house in autocad, a trait picked up in college.  i am a huge diy'er, and have designed the house almost entirely myself, something to be proud of when the project is done.  what i plan to do is all the leg work with the design and structural integrity, and then drop everything off to a structural engineer to have the calculations approved.  yes, building codes will not issue my permits until i have done this.  i have built a few homes but nothing with rooms this size.  it is only a one story dwelling and there will be limited storage above the garage which is the  34' x 25'8" dimensions.  by making a minor design change, which took 5 min. to do on the computer, i am able to run the beam the 25'8" length and then a tributary on each side to receive the joists.  behind the garage there is a 3' breezeway under the same roof.  the roof here is designed as a cantilever with no vertical supports except for the garage wall.  this causes a problem because the joists have to run parallel to the main beam, but has to tie in to a tributary beam.  the roof on the garage will be 8 on 12 with 4 different roof supports angled to where the center of the room does not receive all the loads.  the house will be located in southern louisiana.  i am concerned with the deflection.  in the other room the 29' span, with using 4 - 24" lvl's, the deflection would be 5/8", which i can live with, in the garage over the 25' span i was going to use the same thing, but the engineer at the lumber company mentioned I beams and honestly that had never crossed my mind.  i do have lifting equipment so the weight of the beam shouldn't be an issue.  would there be any advantage to using a lambeam than a lvl?  i tried including a picture but for some reason it wont let me.

 

[jmarkflesher]

Vindingo, Should not you be cutting open people? MARK

 

[fritter63]

One more data point. A fireman once told me that I-Beams ("TGIF joists") are great... except in a fire.....

In fact, IIRC, he said they wouldn't enter a burning structure that had them.

 

[Tim Sproul]

Are regular steel or light steel I beams out of the discussion?

When wood fails from an engineering standpoint, you normally turn to steel.

 

[j123j]

One more data point. A fireman once told me that I-Beams ("TGIF joists") are great... except in a fire.....

In fact, IIRC, he said they wouldn't enter a burning structure that had them.

Steel structures can be dangerous when a fire happens. But these days atleast here where I live they need to be designed to withstand a fire for a good amount of time. Methods include paint (that expands and creates a protective layer), boxing them in "plasterboard", concrete etc etc.

Some steel structures actually have running coolant inside the beams/pilars to transfer the heat elsewhere thereby keeping their structural integrity.

Ofcourse old buildings are what they are...

Steel I-beam or LVL ?
Depends on the loads,span,design... If the lvl cross-section is too big then use steel.

 

[tbellemare]

One more data point. A fireman once told me that I-Beams ("TGIF joists") are great... except in a fire.....

In fact, IIRC, he said they wouldn't enter a burning structure that had them.

Isn't the issue that they don't trust steel supported by wood?

Tom

EDIT:

Fahrenheit 451... Steel? The melting point or temperature at which it will even plasticize is WAY higher.
Steel is really heavy and firemen, though maybe strong, are not Manitowac cranes.

 

[fritter63]

Isn't the issue that they don't trust steel supported by wood?

No, because the OSB in the I-beams burned through much faster than solid joists and made floors collapse on them.

 

[tbellemare]

'Sorry, Fritter...
I see what you're saying, now.

The TGI joists ARE the issue. I thought you were joking about a day off, the last day of the week...

One more data point. A fireman once told me that I-Beams ("TGIF joists") are great... except in a fire.....re.....

Do the firemen typically know the building construction? Are they normally discreet based on the architecture? I don't know any Firemen so I'm sincerely curious.

It would be nice if they had real knowledge of the buildings they were trying to protect.

Tom

 

[fritter63]

'Sorry, Fritter...
I see what you're saying, now.

The TGI joists ARE the issue. I thought you were joking about a day off, the last day of the week...

One more data point. A fireman once told me that I-Beams ("TGIF joists") are great... except in a fire.....re.....

Do the firemen typically know the building construction? Are they normally discreet based on the architecture? I don't know any Firemen so I'm sincerely curious.

It would be nice if they had real knowledge of the buildings they were trying to protect.

Tom

I'm sure it's dependent on the area. In Denver there were large tracts built by the same mega builders, so it would be easy to know in your fire district which ones were built that way.

 

[Holzhacker]

My brother is a Fireman and I used to have various Firemen on my team when I was doing a certain type of inspection work. I haven't had in depth discussions with any of them on this topic. However, based on our general discussions, I can say that they all prefer vintage buildings with real wood. Conditions and times are more predictable.

 

[Nigel]

My brother is a Fireman and I used to have various Firemen on my team when I was doing a certain type of inspection work. I haven't had in depth discussions with any of them on this topic. However, based on our general discussions, I can say that they all prefer vintage buildings with real wood. Conditions and times are more predictable.

I've heard that over here too. Basically steel is too unpredictable and can collapse at any time but solid wood is far easier to read.

 

[jeep jake]

I beams go for about 1 dollar a pound. There is no way you are going to man handle a beam that size. It will cost a ton more to do steel. Generally for residental install will run a additional dollar a pound. However 30ft plus clear span beam will cost more and you will also still have deflection.