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Sistering Joists; Glue and Fastener suggestions


Northern Mike's Avatar
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08-12-13, 06:54 AM   #1  
Sistering Joists; Glue and Fastener suggestions

I will be starting the long process of sistering the floor joists for our main floor.
These have been covered a couple times in different threads. Long story short, 24" C2C, true 2"x8" joists.

For sistering, What product(s) should I look at?
From my reading, nails are generally prefered over screws (personally like screws, but breaking strength is where nails shine). Any specific style?
I will also be looking to glue. Anything specific I should look for in a glue? The original joists are ~1930's.

Doing this more then likely solo, I'm thinking it should be fairly easy to add a beed of glue to the new joist, clamp in place (1 clamp at each end), and once placement is perfect, nail into place. Once nailed, remove clamps, and move to next. Sound about right?

 
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08-12-13, 07:48 AM   #2  
Construction adhesive...PL or Liquid Nail type. As to nails...just regular 12d should be fine. You want to nail from both sides. A pneumatic nailer would really speed up the process, esp since that old wood is probably pretty hard.

May want to use 2 clamps, since it will be pretty hard to hold one end, and then start a nail and hammer it in w/o the new one shifting. Unless you use a framing nailer of course.


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08-12-13, 08:55 AM   #3  
If your doing it by yourself then one clamp in the middle will work, how you going to hold up both ends at the same time? Start nailing in the middle, remove the clamp and nail the rest.

 
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08-12-13, 09:03 AM   #4  
I have a number of good wood clamps from my old speaker construction days.
I was thinking a clamp at both ends, tap into place with a hammer (should they move at all when clamping), then drive a couple nails in each end to secure before moving to the middle. Once there are a couple nails at both ends, I should be able to move the clamps (if needed) towards the center.
I am going to look into a jack if needed (still haven't confirmed how bad the sag is, doesn't visually look to be any).

 
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08-12-13, 11:12 AM   #5  
I'd prepare to have a jack handy anyway. If you have a sag, and the new sister joists are put in "crown up" then there will be no way you will be able to stand the new joist up without raising the old sag out of the way.

Are you going to sister with 2x10's? Rip 2x10's to match true 2x8? or install 2x8's?

 
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08-12-13, 11:27 AM   #6  
czizzi,
I'm going to see if I can get true 8" from one of the local lumber mills. If not, I'll probably go 2x8 as ripping 2x10" will be a very long process.
A quick count looks like ~28x 12ft boards and ~14x 8ft boards. I don't know if my table saw would be up for the task. Notching them to fit would take away from my already low basement (currently ~6'5" from concrete to joist).
I'll be doing solid blocks (bridging) between the joists. Thinking probably 3 each span (~3ft between each).

 
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08-12-13, 11:57 AM   #7  
Considering my basement is only 2 1/2 ft tall, I would kill to have 6 1/2 ft! OK it is only a crawl space but just the same. If you can bankroll the rough cut to match, go or it.

Also keep in mind simple geometry. You are trying to stand up an object that is dimensional. During the "tilting" into place process, you will be trying to get the opposite corners to clear before the flat top of the joists set into place. If you look at the end cut of the 2x8, corner to corner is bigger than top to bottom. To ease the process, you can cut a small bevel on one edge to shorten the gap and ease the install. Have a sledge or maul handy to persuade as you go. Ripping a small bevel would be likened to ripping a 2x10 to match your true 2x8. However, you can do the bevel with a skill saw as the bevel will be hidden against the original joist when installed so "pretty" is not necessary.

 
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08-13-13, 10:23 AM   #8  
IMO, I'd use standard dimensional 2x8 if able to use the existing bottom edge of old joists for ceiling material attachment. Do you require all the extra work for both bottoms flush?

Also, since the old joist is taking (most of ) the bearing now, just cut a taper (think thick, short shim) on the end only/bottom edge of the new joists to allow setting the crown-up distance you need without ripping any material, much quicker...and may not need a jack. Glue the shim before installing after shortening it on point-end to allow for saw-blade thickness you removed with cutting- or more. Keep your 1-1/2" bearing for non-bolt application, though the old one could carry it unless a new heavy load.

Gary
PS. to make up the 5/8-3/4" (as old mill) you could just cut a notch with that extra added to slip a 2x (1-1/2") under it w. glue. Notch (D-4 at ends) allowed; http://arch.umd.edu/Tech/Structural_..._Guide_A11.pdf


Last edited by Gary in WA; 08-13-13 at 10:59 AM.
 
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08-13-13, 08:47 PM   #9  
If you have any sag in your existing joists, jacking that sag to above level will be necessary before you can tilt a new full-length piece into place.

If you don't have any sag now, why are you doing this?

Nailing one end and then lifting, leveling and nailing your way to the other end is often an easier and more effective way to do this. Any adhesive will set up, or at least tack, before you can get to the other end. I'd leave the glue at the store.

I'll be doing solid blocks (bridging) between the joists. Thinking probably 3 each span (~3ft between each)
We used one per span for the 15' spans in our old house. Entertained dozens of people at a time without a jiggle in the floor.

Those were mostly cross (X) braces, and they're better stiffeners, but you should still be OK with a single brace.

 
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08-14-13, 03:54 AM   #10  
Nashkat1,
This is being done due to excessive floor bounce. The joists as mentioned are old (true) 2x8 at a spacing of 24 C2C. With both East and West sides of the house being ~12' spans, walking across the floor in some rooms will make items move (i.e the fridge in the kitchen will rock lightly when you walk past).
The floor surface is original hardwood, and I can not visually see any sag (need to confirm obviously). Subfloor is 1x8(?) plank that runs diagonally.

 
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08-14-13, 05:19 AM   #11  
raise garage floor 20in. ? how close should joist be , how to secure ends. 10ft wide spacing of stuffers.

 
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08-14-13, 02:56 PM   #12  
IMHO, use construction adhesive, not a hot melt glue with a fast set-up time. Wooden furniture, airplanes, boats, drywall, LVLs, GluLams and other engineered products, found it of maximum benefit for minimal cost. Sheathing, decking, and other uses where members act as one and increase strength while reducing/eliminating movement; http://www.google.com/url?sa=t&rct=j...mi-NFA&cad=rja

6 Ways to Stiffen a Bouncy Floor - Fine Homebuilding Article

Gary

 
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