Replacing a structural span

[RTBuilder]

I am looking at moving a span header into the ceiling in my home. The span only supports an attic (with no storage) in a small ca. 1900 home. I would like to support the ceiling joists while I install a new header over top, cut the joists and tie them to the new header using joist hangers. I will eventually have a more structurally competent engineer in to view the design, but is there a good rule of thumb for redesigning a header.

First, is the current header size adequate for an equivalent span if the joists are hung, as opposed to overlapped on top? Second, I have heard that there is a general rule of 1 inch of header depth for one foot of span width - is that generally the case?

 

[FalsePrecision]

We don't use rules of thumb. We use formulas. It is actually a violation of Registration laws to provide specific designs (i.e., tell you you need a 4x10) over the internet, or in this forum. It is legal only to hire a Professional Engineer licensed in your state.

I can answer your general query - it is OK to hang the joists, given the spans or loads are not changed.