Hey all-
I need to cut a joist that has crowned up an inch or two over 10-12 feet to level it out. After level, why wouldn’t 1/2 inch ( or thicker) ply cut to the width of the joist, in 8 foot lengths (4 feet on each side of the cut) nailed and glued to the joist on both sides make it sound??? Seems the plywood on edge like that would be very strong – stronger even the dimensional lumber sistered. I remember a decade or so ago some inspectors allowing trusses to be sistered in this fashion (or maybe to replace gussets where the gusset had torn or split the wood) when I was doing some new construction work.
For that matter, could the technique be used simply for reinforcing joists that have not been cut?
Replies
It wouldn't bother me to do that in certain circumstances.
I dont see any problem with it. I quarentee it will be stonger than before if you do every thing you said.
Tim Mooney
There was an article in JLC a while back on the strength added to beams and headers by the plywood used to thicken them to match the wall thickness.
Basically they said that you only gain strength from the plys that run parralell to the length of the beam.
So adding a piece of 1/2" ply is really like adding a 1/4' of lumber (3/10" if you use 5-ply)
My point is you would get more strength from a 2xwhatever.
Also if you cut the offending member all or most of the way thru in just one spot you will not end up with a straight piece but two bowed ends with a kink in the middle.
My suggestion is to cut not more than 2/3 thru and use a couple 2x's as sisters, with plenty of glue and nailed tight.
Mr T
Do not try this at home!
I am a trained professional!
I used this method recently during remod of a tract house. the house had some bounce in the 2x6 joist the h.o. wanted reduced and I didn't want it under my tile job. I used 3/4 hardwood ply with poly glue and nailed. was very happy with the end result.
If you've got the height available, you could get more stiffness by fastening 2x4 to the bottom edge of the joist. Stiffness goes up as the cube of the joist's height, but only linearly with the thickness.
Thatguy,
You said the joist has a 1"- 2" crown in it, I would snap a chaulkline at the top of the joist from one end to the other and "cut the crown out."
On the the bottom of the joist nail a 2x4 or 2x6 from one end to the other so you have a staight line for sheetrock.
Joe Carola.