Structural considerations for having a transfer beam set flush with the joists.

[davidl13]

I'm working on a home remodeling project where the client wants to take down a load bearing wall and we are proposing to install a beam (most likely LVL) in its place.

I was wondering what structural considerations need to be taken into consideration if we want to make the bottom of the beam flush with the joists so that we maintain clear head space?

In the past I would typically design it as a drop beam and connect it to the joists with simpson hangers. I assume the same can be done with flush beams, but I imagine there might a different approach with the calculations (perhaps a reduction factor of some sort?).

Any advice/direction on this would be greatly appreciated!

 

[dik]

If dimensioned lumber, you want to have about an inch between the top of the steel beam and the top of the wood joists to accommodate any shrinkage of the dimensioned lumber.

 

[davidl13]

If dimensioned lumber, you want to have about an inch between the top of the steel beam and the top of the wood joists to accommodate any shrinkage of the dimensioned lumber.

In my case, I'm trying to get a wood beam to work as the transfer beam in place of the load bearing wall. I'm thinking something like a (2) 2x10 LVL but need to run the numbers to confirm.

So you're saying that there should be about a 1" gap like so? See attached image.

 

[phamENG]

No, you shouldn't have any gap. dik thought you were using a steel beam.

Is the top of the beam restrained? If not, you'll need to modify your design accordingly. Are you in the US? If so, the NDS has everything you need - you should be going through all of your adjustment factors and you'll see that having the top of the beam not restrained does, indeed, reduce your capacity.

 

[davidl13]

No, you shouldn't have any gap. dik thought you were using a steel beam.

Is the top of the beam restrained? If not, you'll need to modify your design accordingly. Are you in the US? If so, the NDS has everything you need - you should be going through all of your adjustment factors and you'll see that having the top of the beam not restrained does, indeed, reduce your capacity.

Thank you for the advice!

I do live in the US and will definitely look into the NDS for this. I was also considering to use Forte to design the beam and can double-check by hand using the NDS.

Since they don't want this beam exposed and want it to be flush with the floor joists above, that would mean the top of the beam will be unrestrained. Are there any other considerations I need to take into account for designing a flush beam that's different from a regular drop beam?

And are there any fasteners you would recommend for connecting the joists to the flush beam?

 

[phamENG]

Best thing I can recommend is to go through the NDS, but also pick up a copy of Breyer's 'Design of Wood Structures'. It's an excellent primer on engineered wood design.

Do not use Forte unless you can do the design by hand. It's easy to use - almost too easy. There are ways to also misuse it and think you have a safe design when really you don't. If you do use it, make sure you look very closely at all of the inputs AND outputs and ensure you know exactly what they mean.