Can I stack new beam to the top of old beam to extend span?

Question

I have appropriately sized an LVL to extend a span by 3ft as well as assured the column support to the foundation at the new column.

EDIT: The existing 12 ft span is carried by a 4x10, the new span is 15 ft and would be carried with the appropriate full-length LVL

The existing simple span is a 4x10 beam with 2x8 ceiling joists. It had been my intention to build the temporary support walls, remove the existing beam, place the new LVL beam and re-hang the joists.

A competent framer told me that I could save work by setting the new LVL on top of the old beam then connect them with metal fasteners. In this way, I would only need to hang a few additional rafters from the new beam and would not need to build temporary walls or remove the existing beam.

The LVL is oversized so the additional weight of the 4x10 is negligible.

This method stands to reason in my mind and I would likely add some timber to keep the beam from yaw/roll anyhow.

Is this a common/acceptable practice? It seems perfectly plausible to me but I had never heard of doing this before.

Answer 1

There is no problem flush framing the LVL in the ceiling as you suggest, provided it physically fits in the space available. If the LVL is placed directly over the 4x10, the ceiling joists will need to be cut to make room for the LVL. If this cutting keeps them from bearing on the 4x10, they need to be shored up until the LVL and hangers can be fitted. A temporary ledger on the 4x10 will suffice. Since LVLs can be narrower than sawn timbers, shoring/ledger may not be needed.

You might consider removing the 4x10 beam to open up the new opening so it is taller. Once you remove the supporting walls, it will more or less fall down anyway, unless it is well attached to the new LVL, essentially hanging it beneath the LVL. Why leave it there? It's not doing anything but getting in the way. Unless it's hiding the end of a soffited area, the taller opening would be an added benefit of flush framing the new LVL.