carpentry question - strapping ceiling, shimming to level

[mound]

Regarding prepping an old ceiling for drywall and wanting to make it flat and level....

I located the lowest point in the whole ceiling and have a 360* laser level I can use to show me how much I need to bring down any given joist.

I've seen folks sister "two-by" material to the joists to bring them down. 

Two-by material is expensive and I have a lot of extra 3/4" plywood.. if I were to rip the plywood into 6" strips, screw and glue those to the joists offset down to the level line, is the 3/4" edge of plywood suitable to attach 1x3 strapping to with 2" ring-shank 10d nails?

Or would I be better shimming down the strapping and still nail it to the joists? (I edited this post to use the word shimming, apparently the same word but without the "ming" at the end is masked out by the woodnet forum code as foul language!)

[jteneyck]

Regarding prepping an old ceiling for drywall and wanting to make it flat and level....

I located the lowest point in the whole ceiling and have a 360* laser level I can use to show me how much I need to bring down any given joist.

I've seen folks sister "two-by" material to the joists to bring them down. 

Two-by material is expensive and I have a lot of extra 3/4" plywood.. if I were to rip the plywood into 6" strips, screw and glue those to the joists offset down to the level line, is the 3/4" edge of plywood suitable to attach 1x3 strapping to with 2" ring-shank 10d nails?

Or would I be better shimming down the strapping and still nail it to the joists?  (I edited this post to use the word shimming, apparently the same word but without the "ming" at the end is masked out by the woodnet forum code as foul language!)

I've never done what you need to, but I would not use plywood on edge if I were to do it.  Edge grain plywood has poor screw/nail holding ability.  lf I wanted to do it at low cost I've use cedar shims between the strapping and joists, where and as needed, and screw the strapping directly into the joists.  If your joists are way out of whack in some places, like more than what two shims can handle, then I'd add a small piece of plywood against the joist so that I'd still only need two shims, and use appropriately longer screws.  

This will likely take longer than if you were to use 2X material to get everything level first, but having the laser should still make it go pretty quickly and a heck of a lot easier than w/o one.

John

[mound]

I've never done what you need to, but I would not use plywood on edge if I were to do it.  Edge grain plywood has poor screw/nail holding ability.  lf I wanted to do it at low cost I've use cedar shims between the strapping and joists, where and as needed, and screw the strapping directly into the joists.  If your joists are way out of whack in some places, like more than what two shims can handle, then I'd add a small piece of plywood against the joist so that I'd still only need two shims, and use appropriately longer screws.  

This will likely take longer than if you were to use 2X material to get everything level first, but having the laser should still make it go pretty quickly and a heck of a lot easier than w/o one. 

John

Thanks John.  Agreed on the edge of plywood, now that I think of it, wouldn't rely on it to hold a nail or screw.
What about using more of the 1x3 strapping material vertically along the joists to bring them into the level plane? Is 3/4" solid wood enough to nail the strapping to? 

Barring that, shimming between the joists and the strapping is the route I'll try to go. I'd hate to have to go buy ~30  12' 2x6s to accomplish this. 

The distance between the lowest point and the highest point on the ceiling is just under an inch.

[MstrCarpenter]

O.K.. First, if the box label says 10d and your tape reads 2" one or both are wrong. 2" nails (6d) are too short for strapping, so let's assume they're 3" (10d) ring shank. 8d ring is what I usually use, but with up to an inch of shims, 3" is better. If there are only a few extremely low spots, I would notch the joists a little to take the curse off. Several shallow cuts with a Skil saw followed with a straight claw hammer works well enough. Now here's the secret trick I was taught for leveling strapping. (So don't tell anyone!) Grab your finish gun with 8d (that's 2-1/2" for those not paying attention) and just tack up all the strapping on the outboard edges, skipping every other joist. Now you'll just need a bunch of 1-1/2" to 2" wide shim-shingles. The strapping will easily come down as you tap the shims in to final elevation. When they're all shimmed flat, go ahead and nail it off with the 10d ring. Now you can go back to shim the ones you skipped with only a 4' straight edge to verify the strapping is flat across the 32" span.

If using a laser level, I put up a shelf so the laser beam is 1/2" or 3/4" below the bottom of my strapping. I can eyeball a half inch where the laser beam hits the side of my hammer or a shim shingle and I always have one of each in my hands.

[mound]

O.K.. First, if the box label says 10d and your tape reads 2" one or both are wrong. 2" nails (6d) are too short for strapping, so let's assume they're 3" (10d) ring shank. 8d ring is what I usually use, but with up to an inch of shims, 3" is better. If there are only a few extremely low spots, I would notch the joists a little to take the curse off. Several shallow cuts with a Skil saw followed with a straight claw hammer works well enough. Now here's the secret trick I was taught for leveling strapping. (So don't tell anyone!) Grab your finish gun with 8d (that's 2-1/2" for those not paying attention) and just tack up all the strapping on the outboard edges, skipping every other joist. Now you'll just need a bunch of 1-1/2" to 2" wide *****-shingles. The strapping will easily come down as you tap the shims in to final elevation. When they're all shimmed flat, go ahead and nail it off with the 10d ring. Now you can go back to ***** the ones you skipped with only a 4' straight edge to verify the strapping is flat across the 32" span.

If using a laser level, I put up a shelf so the laser beam is 1/2" or 3/4" below the bottom of my strapping. I can eyeball a half inch where the laser beam hits the side of my hammer or a ***** shingle and I always have one of each in my hands.

Thank you! I wasn't reading the box, just typing quickly and sorta misspoke. What I was going to use (because I have a full box of them) are Paslode 3"x0.131-Gauge ring-shanked hot dipped galvanized nails. I realize they are for exterior framing, but like I said, I have them..  

(so far I've actually only tacked them in place using a finish nailer every other joist or so, just like your trick! Seemed like a good way to get things up first in a way that can still be shimmed down.)

I've found the lowest and highest points using the 360 laser level, it's not as bad as I thought. The highest part is about 7/8" above the lowest part, so everything has to come down, nothing has to go up, but notching the joists as you describe is a cool trick.

Gotta love how the word "s-h-i-m" is being blanked out as if it's a bad word. I put a note about that in the woodnet forum features area for a mod.

[MstrCarpenter]

Thank you! I wasn't reading the box, just typing quickly and sorta misspoke. What I was going to use (because I have a full box of them) are Paslode 3"x0.131-Gauge ring-shanked hot dipped galvanized nails. I realize they are for exterior framing, but like I said, I have them..  

(so far I've actually only tacked them in place using a finish nailer every other joist or so, just like your trick! Seemed like a good way to get things up first in a way that can still be shimmed down.)

I've found the lowest and highest points using the 360 laser level, it's not as bad as I thought. The highest part is about 7/8" above the lowest part, so everything has to come down, nothing has to go up, but notching the joists as you describe is a cool trick.

Gotta love how the word "s-h-i-m" is being blanked out as if it's a bad word. I put a note about that in the woodnet forum features area for a mod.

I have a business aquaintance that says; "We strive for perfection, but excellance will be tolerated." In that world, "shimm" is a bad word.

[EdL]

I've found it easiest to sister steel studs to the existing rafters.
Big advantage is they are straight to begin with...

If you do, make sure to use fine thread drywall screws to hold the new drywall up, thats why they exist.

Ed

[crokett™]

It would be a lot easier to sister 2x4s to the existing rafters then try to s-h-i-m strapping across them.  Sistering all you have to do is attach the 2x4 so it hits the laser on both ends.  Strapping you  have to separately shim each piece  at each rafter.

[mound]

Thanks all. 
I thought about steel studs. a lot more expensive than any other route.

I did a sort of combination of all the ideas presented.  I used a 360* laser level to set a reference position. I sistered 1x3 strapping (not 2x4's or 2x6's) to the joists to the reference line to create a flat plane which was level with the lowest point in the room. 

Then, I attached more 1x3 strapping perpendicular to the joists and tacked them in place with brad nails to the 1x3 strapping which I had sistered to the joists. So the sistered material didn't exist for me to attach the strapping directly to (other than the quick brad nail tacking in place), rather, to act as the spacer/s-h-i-m. This was easier than trying to s-h-i-m down each intersection on its own.    

Finally, 3.5" screws through the strapping into the joists (not the sistered material) at each intersection.  So there's a gap between the strapping and joist, you can see the screws in this gap, but the sistered 1x3 acted as a spacer that was beefy enough not to deflect as the screw was driven right next to it into the joist. 

worked great!