Reinforcing 2x6 attic joists above 2nd for conversion to 3rd floor living space?

Seeing if anyone can help, I just bought a house built in 1908. Half of the attic was a finished with plastered and deteriorated over the years due to a leaky roof, the other half of the attic was unfinished. I Just got a ne w roof on and recently Demo'd the plaster and ulitmatley pulling up the ton gue and groove subfloor to run new electrical to the 2nd floor. The joists are now exposed and I found a pipe in the floor that was once fully connec ted for radiant heating. With that said someone notched out the joists to cut across with the pipe and now when I stand directly on those joists (3 o r 4 of them) the floor beam feels pretty "spongy" now. I am wondering if t his is a cause for concern? And if so, can and should I sister a 2x6 to the existing joist for more support. Also a quick mention I plan on redrywall ing the room directly below this room (putting 1/2" drywall over top of the existing plaster). I should also say these joists will at a part in the floor where it is not walkable because I will be putting knee walls in. I also plan on putting i n a 3/4" subfloor.
Does Anyone have any ideas or suggestions ?
Thanks Rex
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The existing joists are 2 x 6? How big is the notch? 2 x 6 is a little too small for an occupied floor, you might want to double them all, even if they are not notched.
r.
On Fri, 21 Apr 2017 22:43:59 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

with plastered and deteriorated over the years due to a leaky roof, the other half of the attic was unfinished. I Just got a new roof on and recently Demo'd the plaster and ulitmatley pulling up the tongue and groove subfloor to run new electrical to the 2nd floor. The joists are now exposed and I found a pipe in the floor that was once fully connected for radiant heating. With that said someone notched out the joists to cut across with the pipe and now when I stand directly on those joists (3 or 4 of them) the floor beam feels pretty "spongy" now. I am wondering if this is a cause for concern? And if so, can and should I sister a 2x6 to the existing joist for more support. Also a quick mention I plan on redrywalling the room directly below this room (putting 1/2" drywall over top of the existing plaster).

I will be putting knee walls in. I also plan on putting in a 3/4" subfloor.

Remove 333 to reply. Randy
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.