I have a 112 year old full 2″x full 8″ joist that has developed a crack about 18″ long, starting 3′ from the interior supporting wall, and about 3″ from the bottom of the joist. The span is 14 feet, but there is no load at all on 3′ of that at the exterior wall end. The crack does not appear to be new and is not all the way through. There is virtually no sag on that joist. There is not much (dead) load on the floor above – child’s bedroom, far enough out from wall no furniture – but not in middle of room.
Unfortunately there are 3 different spots where electrical cable runs through the joist – between 3.5″ and 4″ from the bottom of the joist. Due to the mammoth effort involved to re-route all the electrical I would far prefer to fix the joist without laminating a full other 2×8 to it.
I would propose to salvage the situation by jacking the cracked portion up from below, and gluing and drilling and then screwing a 2 x 4 using 3.5″ #10 screws every 12″, for the full length, to each side, flush with the bottom edge, and then letting it cure for a couple of days.
Any thoughts on the wisdom of this approach greatly appreciated.
Gavin Pitchford
Replies
I'd try 3/4 ply, it will have more lateral strength than a 2x4. you can notch it for the wires. Then glue & screw. Double up if ness. IMHO
Can't I go 1 day without spilling my coffee?
Can you post a picture? It will be worth at least market value (1000 words) maybe more.
From the way I (a mere smart alek 12 yo steelin time at pops computor) understand your post, about 3" from the bottom of the joist...and is not all the way through, you may not have a serious problem. The bottom 1/3 of the joist is in tension. You may have a house ready to fall down, can't tell from info given.
What danger lurks in the hearts of joists? Only the engineer knows.
SamT
Edited 5/1/2003 1:41:46 PM ET by SamT
I like the plywood idea. Makes sense. How far up - all 8" ?
No picture - and unfortunately, the whole thing ain't gonna fall down - though that would be nice... faster to start over ! It is just this one joist. The crack is small enough I didn't even notice it until AFTER I had put the drywall on the walls and part of the ceiling. There is a knot which it appears to have cracked around. The crack does not go all the way through, and the only part which comes comes to the bottom of the joist runs parallel to the joist for about 3 inches, and about a 1/4 inch from one edge. It's almost more like a shear. I have been watching it for about a month now I know it's there, while doing other things and it is not getting any worse.
I have also had a 100 lb. kid jump on it from above and the flex is less than negligible.
I suspect that the 3 tons of lath and plaster and mesh bolted to the ceiling had been preventing it from flexing for the past 100 years, and without the tension on the lower edge for the past 3 months it may have widened a bit.
Gavin Pitchford
If I were going to use the plywood method, I would use it on either side of the joist, and sandwich the joist between using bolts 1/3 from top and 1/3 from bottom every 16" oc.
But then I just like overkill.Never be afraid to try something new. Remember, amateurs built the ark, Professional build the Titanic.