The beam is too deep Mr. Engineer

[ANE91]

12-foot span supporting two residential stories, (2)14” LVLs flush, joist bays are 12’ and 16’, contractor wants 9-1/4” instead. Deflection controlled. No chance of reconfiguring the floor plan to cut down the trib width or add interior supports. I can’t think of a way to make this work…5 or 6 LVLs feels like crazytown. Any creative ideas before I crush his dreams of a mildly taller ceiling?

I’m sure there’s plenty of other posts about this exact topic, but I wanted some contemporary feedback while I searched. Thanks y’all.

 

[jhnblgr]

Did you look at glulams or steel beam? Forte web would be an easy check

 

[Eng16080]

Seeing a floor plan would be helpful.

Some ideas:

1. Use a steel beam. I would bet a W8 section works for your loads and fits within the desired floor depth.
2. Use a flitch beam (for ex. 2 LVL plies with a steel plate sandwiched between).
3. If the floor plan allows it, push the beam up into a wall above. This only works if there aren't any wall openings which would be obstructed by the beam.

I usually go with option 1 in this situation.

 

[XR250]

W8 would be my choice

 

[ANE91]

Contractor has historically turned his nose up at steel beams for whatever reason. They can't be that much more expensive, can they? Plus I don't want it bearing on wood, so then we'd need to hide steel tubes in the walls...doable but I doubt he'll go for it. Contractors really like LVLs here...

Also found this, if I really have to go this direction: https://www.eng-tips.com/threads/multiple-ply-lvl.432811/. WestFraser and Weyerhauser do not seem to list values for more than 4 plys, though. Seems like I'll have to widen my bearings either way. I didn't budget for this, so I'm gonna push back for now. Thanks y'all.

If the floor plan allows it, push the beam up into a wall above. This only works if there aren't any wall openings which would be obstructed by the beam.

Intriguing. Can you share a detail?

 

[JAE]

You gotta do what's right - not what the contractor tells you to. I assume you'll do what's right but at some point I've had to tell contractors that I'll draw whatever they want done as long as they take responsibility for it after I leave the project.

 

[Eng16080]

Contractor has historically turned his nose up at steel beams for whatever reason. They can't be that much more expensive, can they?

Based on some recent research I did, no, steel is not necessarily more expensive than LVL beams. I actually found it to be slightly cheaper based on comparing costs of an LVL beam with a steel beam of similar strength.

The contractor doesn't get it both ways. Let them either choose steel and the ceiling height they prefer or LVL and a deeper ceiling. There's nothing about steel that should be a deal breaker for a good builder.

Plus I don't want it bearing on wood, so then we'd need to hide steel tubes in the walls...

I held this belief for many years that a steel beam must be supported by a steel column. After giving it more thought, I couldn't think of a good reason why. If a PSL post or other wood column has adequate capacity, why not support it on that?

Intriguing. Can you share a detail?

Sure, here's one from a recent project where I needed a 16" LVL beam but the floor depth was only 11 7/8". I usually don't go overboard with this. For example, I probably wouldn't use something like a 24" deep beam where then it becomes questionable if the top of the beam would be laterally braced against buckling.

 

[XR250]

I went to a job recently where they had constructed that detail but ended up adding a door so they cut a 6" deep notch x 36" in the top LOL.

 

[Eng16080]

I went to a job recently where they had constructed that detail but ended up adding a door so they cut a 6" deep notch x 36" in the top LOL.

That's ridiculous. I'm guessing nobody thought twice about making the cut either!

Normally I reserve this detail for exterior walls, but in the case above, it's for an attic kneewall, where no access doors are shown. I still have a little fear they could do this, although luckily the builder on that project is really good.

 

[271828]

I went to a job recently where they had constructed that detail but ended up adding a door so they cut a 6" deep notch x 36" in the top LOL.

That was my first thought.

If the potentially notched beam is strong enough, I might go for it. Deflection might still be ok or close to ok with only a door sized segment with reduced EI.

 

[ANE91]

I held this belief for many years that a steel beam must be supported by a steel column. After giving it more thought, I couldn't think of a good reason why. If a PSL post or other wood column has adequate capacity, why not support it on that?

Could the reason be related to providing rotational restraint at wood bearings? I know this can be done with a flange plate bolted to the wood, but that can be messy.

 

[phamENG]

Another issue with the beam upset into the wall above is bracing. I've had trouble convincing myself that it's adequately braced unless joists are at least 2/3 of the depth of the beam and perpendicular to it in both directions without some funky detailing that residential contractors hate. I'll use it at exterior floor offsets where they put a little shallow slope shed roof in to cover the offset - I can often place the beam so the rafters catch the top edge.

 

[Eng16080]

Could the reason be related to providing rotational restraint at wood bearings? I know this can be done with a flange plate bolted to the wood, but that can be messy.

This could be an issue for a deeper steel beam, but for something like a W8 bearing on a PSL post, I don't think it's a concern. I should note that my typical detail has a 1/4" end plate welded to the beam and 1/4" vertical steel tabs which extend down opposing sides of the PSL and have holes for thru bolts.

From a recent job:

 

[Eng16080]

Another issue with the beam upset into the wall above is bracing. I've had trouble convincing myself that it's adequately braced unless joists are at least 2/3 of the depth of the beam and perpendicular to it in both directions without some funky detailing that residential contractors hate.

I agree with these points and generally try to follow this. I suppose in my detail above it's debatable if the lateral bracing is from both sides.

 

[phamENG]

From a recent job:

This is more or less my go to as well. Just have to make sure it's within the wall, and that the bolts aren't going through the wrong face of the glulam, built up post, or SCL column.

I suppose in my detail above it's debatable if the lateral bracing is from both sides.

Depending on what sort of brace force is needed, 2 or 3 joist spacings of solid blocking at 2' o/c may be enough. If only on one side, periodic tension ties to ensure the bracing works in both directions with enough blocking to engage the diaphragm.

 

[Ron247]

I would consider the flitch beam already mentioned if it can work.

 

[XR250]

I would consider the flitch beam already mentioned if it can work.

For me flitch beams are not good at shorter spans as the end reactions are typically very high. I would take an I-beam any day over a flitch in this situation.
1) The i-beam will be cheaper as it is more efficient
2) Having confidence in getting the plate loading into the wood at the supports with high loading is sketchy at best. I generally add a bearing plate under them to keep the plate from knifing thru the support.

They do have their place though. I like them better for one-sided loading.

 

[phamENG]

I generally add a bearing plate under them to keep the plate from knifing thru the support.

What about detailing it so that it's shallower than the wood, and held 1/4" to 1/2" above the bottom of the wood plies? That's my go-to...curious if you've seen issues with that approach in the wild. I haven't gotten complaints, but then I wouldn't be surprised if they just spray painted a piece of plywood black to trick a city inspector...

 

[jerseyshore]

Contractor has historically turned his nose up at steel beams for whatever reason. They can't be that much more expensive, can they? Plus I don't want it bearing on wood, so then we'd need to hide steel tubes in the walls...doable but I doubt he'll go for it. Contractors really like LVLs here...

I have a 21ft long W12x26 in my kitchen on two steel columns and the price of the steel vs 18" LVL's was cheaper for the steel. Engineered lumber is expensive these days.
The cost difference is usually in the installation because not all contractors want to work with steel beams. Also they can be heavier to move since they are in one piece and not separate plies. Either way steel beams all day.

I went to a job recently where they had constructed that detail but ended up adding a door so they cut a 6" deep notch x 36" in the top LOL.

Saw the same thing. I never upset beams unless it's in an uninhabitable attic because they always get messed up.

For me flitch beams are not good at shorter spans as the end reactions are typically very high. I would take an I-beam any day over a flitch in this situation.
1) The i-beam will be cheaper as it is more efficient
2) Having confidence in getting the plate loading into the wood at the supports with high loading is sketchy at best. I generally add a bearing plate under them to keep the plate from knifing thru the support.

They do have their place though. I like them better for one-sided loading.

These days for non-LVL beams we design probably 95% W shapes and 5% flitches. Steel flitch plates are way $$$$. And over the last 5 years or so steel beams in residential are way more common. Rarely do we get pushback.

What about detailing it so that it's shallower than the wood, and held 1/4" to 1/2" above the bottom of the wood plies? That's my go-to...curious if you've seen issues with that approach in the wild. I haven't gotten complaints, but then I wouldn't be surprised if they just spray painted a piece of plywood black to trick a city inspector...

We always show the flitch plates being shallower than the wood, but flush to the bottom. No way to transfer the shear at the end thru bolts into the columns with heavy flitches. Need the steel plates to bear directly on the PSL post and/or steel bearing plate.

 

[SE2607]

I went to a job recently where they had constructed that detail but ended up adding a door so they cut a 6" deep notch x 36" in the top LOL.

If something like that happened on one of my projects, right after the jobsite visit, my next call would be to the state contractor's license board and would be persistent until I receive evidence that the contractor had lost his/her license.