We have a 1" sag in our floor along one joist and around 1/2" sag in the joists on either side. The low spot on the floor is in the center of the span and the floor has some bounce in it. I have located the problem and it's a floor joist that was completely cut when the house was built 20+ years ago for a plumbing drain. No support or braces were added. The low spot is where the refrigerator was located (now moved) In addition to the joist that was cut, the joists on either side of the cut joist also appear to be sagged a small amount and in the basement I noticed they have holes drilled out of the bottom 2" for an electrical line. What a mess from shoddy work.
My plan is as follows: I have a LVL board to sister to the cut joist. The LVL is a14' "2x10" and all my joists are 14' 2x8's. I am going to rip the LVL to the size of a 2x8. I plan to turn the LVL on it's side and push it over the beam in the center of the house, then slide it back over the sill plate on the outside wall and rotate it up on it's end. It will be screwed or bolted to the existing joist and PL Premium construction adhesive used. On either side of the cut joist, I will be sistering boards to the those joists as well. I plan to pull back the electrical wires that are currently running through the joists and run those down the center support beam and then through the joist cavity to the light outlet so no joist drilling is required.
There are a couple of issues/Questions:
- The new joists are 7 3/16" tall and the old joists are 7 3/32" Should I rip them 3/32" smaller or just the ends? Also to rotate them into position do I need to radius the corners?
- Screw or bolts? My Father in law said bolts might make it look like there is a more serious problem to a buyer later on if we ever sell.
- At a minimum, I am sistering the cut joist with the LVL and sistering new 2x8's to the joists on either side for a total of 3 sistered joists. The question is with the sequence for attaching the new joists. I have a 4x6 beam for jacking, 3 screw adjustable columns and a bottle jack. I would like to use PL Premium and screws or bolts. PL Premium says it has a 30 minute working time for repositioning the materials to be bonded. So do I get all 3 joists laying on the 8" side then jack up the three joists until the floor above is flat, then apply the PL to one board, turn it on it's side, clamp it together and then screw/bolt that entire joist before going on to the next? I have a feeling turning them up and attaching them is NOT going to be a piece of cake because of the sag. If I wasn't using construction adhesive I imagine I would jack up the old and new joists all 3 at the same time, make sure the floor above is level, then secure everything.
- Do I install it with the floor slightly higher than it needs to be to overcorrect the sag?
- In the areas like the stairwell where I can't slide the joists over the center beam so my options seem only to have one end of the sistered joist resting on a support wall - is this still worth doing? is there another way to support them maybe with a joist hanger or bracket?
The reason I got an LVL beam was I thought I needed something stronger than just another 2x8 joist to overcome 20 years of sag.
Thanks for any advice- here are pictures and a video to better illustrate my situation:
Here is a link to the Video:
Jumpcut - Flooring sag joist repair
Linear Mode
