So the primarily joist in my basement is 2×10, and all I could get locally (due to stay at home order) was 2×6 x 8. I have to notch the joist in a spot and wanted to practice sister it at least 3 ft on each side. However, a one person job resulted in a 1/2 gap between the top of sister joist and floor, so it’s not flush with the primary joist. Is all hope lost in this sister joist supporting the primary joist? I did use a pretty solid nail pattern and generous adhesive.
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To me, properly sistering a joist means installing a new joist identical to the old one - same width, same length, supported at both ends - fastened with nails and adhesive.
What is the length/span of the original 2'x10' joist? What is the dimensions of the notch and where is notch located in relation to the end of the joist.
The original 2x10 is 18 ft. The notch is about 2 inches Long, and 2 inches high and is working 5ft of the wall, so I would say within the first 1/3 of the wall. I just wanted to brace it incase it’s a problem. I didn’t know if the board would still service as a brace or not.
I don't think that a 2"x8"x8'-0" is going to do much but it won't hurt. like plumb 13 said, that is not really sistering.
1/2 inch gap means the load is not being carried by the "sistered" joist, however, it may keep the original joist from flexing/bending.you could rip down some 2x material to fill the space
other question is notch at the top or bottom of the joist - saw something years ago about adding a 2x4 to the bottom of a notched joist creates an I-beam (I-joist?) effect and reduces the flex caused by notching the joist.
also, did you have to notch the "sistered" joist as well?
As my structural engineer says, "the beam will only be as stiff as its stiffest member. All the additional 'sisters' will only be adding weight for the stiffest member to carry." 2x10 with 2" notch is only a 2x8. 2x6 "not supported" is only added weight, not a sister joist. Thickening a joist is the most expensive way to gain stiffness. Add depth and you will gain exponential increases in stiffness. Even regain the depth lost by the notch once it becomes a 'hole'.
so adding a 2x4 on the bottom (creating an inverted T ) works by adding depth to the existing joist (structure)?
guessing the added depth has to be along the entire length of the joist?