sister joist Cracked Floor Joist Sistering, Nailing

[pbgvdad]

1.  Several 2”x12”x16’ floor joists under a corner bedroom are showing signs of cracking and the floor is squawking in a 26 year old home.  This seems to have begun or to have accelerated within the past 6 months or so.  There is no sign of basement block wall cracking under the corner bedroom where the cracking joists are located.  There are also no signs of plaster damage to walls or ceiling in the bedroom.  The door from the bedroom to the adjacent bathroom started to hit the bathroom plank tile floor about a year ago.  The only “heavy” load is a dense foam queen size mattress where an elderly 200 lb. person sleeps.  What could be causing the joists to fail?

2.  I want to jack the joists level and sister the worst joist with a 2”x12”x12’ board which will span the support on top of the outer block wall and a basement load bearing wall.  I plan to use a few bolts and adhesive to hold the sister joist in place against the damaged joist, then nail them together before the adhesive dries.  I want to nail from the sister side to help drive the joists together.  However, the original joists are spaced at 16”, so the space between the sister joist and the next joist is only 13”  [16 - (2x 1-1/2)].  Since the framing nail guns I am considering are taller than 13” (more like 13-1/2”), is it acceptable to nail the joists together with the gun slid between the joists so the 3” nails are driven at an angle?  

Edited August 28, 2020 by pbgvdad

[Marc]

7 hours ago, pbgvdad said:

1.  Several 2”x12”x16’ floor joists under a corner bedroom are showing signs of cracking and the floor is squawking in a 26 year old home.  This seems to have begun or to have accelerated within the past 6 months or so.  There is no sign of basement block wall cracking under the corner bedroom where the cracking joists are located.  There are also no signs of plaster damage to walls or ceiling in the bedroom.  The door from the bedroom to the adjacent bathroom started to hit the bathroom plank tile floor about a year ago.  The only “heavy” load is a dense foam queen size mattress where an elderly 200 lb. person sleeps.  What could be causing the joists to fail?

2.  I want to jack the joists level and sister the worst joist with a 2”x12”x12’ board which will span the support on top of the outer block wall and a basement load bearing wall.  I plan to use a few bolts and adhesive to hold the sister joist in place against the damaged joist, then nail them together before the adhesive dries.  I want to nail from the sister side to help drive the joists together.  However, the original joists are spaced at 16”, so the space between the sister joist and the next joist is only 13”  [16 - (2x 1-1/2)].  Since the framing nail guns I am considering are taller than 13” (more like 13-1/2”), is it acceptable to nail the joists together with the gun slid between the joists so the 3” nails are driven at an angle?  

There's something missing that makes me hold back on making any suggestions.  The resident and foam mattress aren't the problem.  Something else is.

[Jim Katen]

10 hours ago, pbgvdad said:

1.  Several 2”x12”x16’ floor joists under a corner bedroom are showing signs of cracking and the floor is squawking in a 26 year old home.  This seems to have begun or to have accelerated within the past 6 months or so.  There is no sign of basement block wall cracking under the corner bedroom where the cracking joists are located.  There are also no signs of plaster damage to walls or ceiling in the bedroom.  The door from the bedroom to the adjacent bathroom started to hit the bathroom plank tile floor about a year ago.  The only “heavy” load is a dense foam queen size mattress where an elderly 200 lb. person sleeps.  What could be causing the joists to fail?

2.  I want to jack the joists level and sister the worst joist with a 2”x12”x12’ board which will span the support on top of the outer block wall and a basement load bearing wall.  I plan to use a few bolts and adhesive to hold the sister joist in place against the damaged joist, then nail them together before the adhesive dries.  I want to nail from the sister side to help drive the joists together.  However, the original joists are spaced at 16”, so the space between the sister joist and the next joist is only 13”  [16 - (2x 1-1/2)].  Since the framing nail guns I am considering are taller than 13” (more like 13-1/2”), is it acceptable to nail the joists together with the gun slid between the joists so the 3” nails are driven at an angle?  

2x12 joists on 16" centers spanning 16' should not be cracking unless you've got elephants dancing on them. The dragging door is not important here. 

What makes you think that the joists are cracking? Do you have pictures? Do you know what checking is? 

My gut tells me that you're trying to fix a problem that doesn't exist. 

If you drive the nails in at an angle, it will not draw the joists together, but hold them apart. You'd need to clamp them together first, then drive the nails at an angle. Alternatively, google "palm nailer."