help me with framing questions

TomM · Post by **TomM** » Thu Dec 22, 2005 12:30 am

I'm building a studio in my basement. I think building the frames in place is a good idea so I can have a tight fitted frame without space between the top plate and ceiling joists.

Would this be recommended? Or is it better to build a frame first and then use something on the top plate that connects it to the joists that helps isolation?

Sound proofing is what i'm after.

TomM · Post by **TomM** » Thu Dec 22, 2005 2:08 am

I'm thinking now that it's better to build the frame first and use sway braces to attach the top plat to the joists above....

how much space should be between the top plate and the joists??

knightfly · Post by **knightfly** » Fri Dec 23, 2005 4:42 pm

It only takes about 1/4" gap to be able to tip a 2x4 stud wall into place after it's built on the floor -

Inner wall frames will perform better for isolation when they are NOT wedged hard between floor and ceiling joists - the "floppier" the framing in a sound wall, the better.

Floor joists (which is what your studio's ceiling really are) are normally spec'd on what they call "L/360" - what this means is, if you divide the total length of your span (in INCHES) by 360, that's the allowable vertical deflection of that joist.

Example - you have a 12 foot span on a floor joist (the ceiling joist of your basement) - this = 144 inches. 144/360 = 0.4 inches. This is the maximum your joist will deflect as long as you don't exceed original specs (by adding more weight, for example) -

What this means is that your basement's ceiling can move downward by 4/10 of an inch and it's perfectly normal.

Sooo, if you don't want your inner walls to come into hard contact with the ceiling joists, they shouldn't be closer to the ceiling joist than 4/10 inch.

Except for one detail - this maximum deflection is calculated for the MIDDLE of the span - near a hard support, such as a basement wall, things won't move as much. So if your inner walls are within a foot or so of the perimeter, 1/4" is enough.

If you put some sort of rubber between your wall frames and the ceiling joists, you should leave a gap IN ADDITION to that rubber - that particular rubber should be considered a "contingency" plan, NOT a resting place. During operation, you don't want your walls compressed vertically by the rest of structure.

The rubber you use on either SIDE of a sway brace DOES need to make firm contact in order to positively locate the top of the frame for stability.

When attaching wallboard to your frames, be sure to follow the suggestions in the REFERENCE section - use backer rod before each caulk bead, offset ALL joints in successive layers, mud and tape and sand between layers, etc... Steve

len-morgan · Post by **len-morgan** » Tue Dec 27, 2005 11:48 pm

Have I missed something or is TomM suggesting connecting his new walls DIRECTLY to the floor joists above and hoping for sound proofing?!

I didn't see any mention of using RC to attach the ceiling drywall to the floor joists so it sounds to me like he is planning to build a giant sound CONDUCTION room instead of an isolation room.

If you really need sound proofing, you should build and stand your walls WITHOUT touching your floor joists, then put new ceiling joists resting on your new walls in between the floor joists. This will give you the maximum height and a completely sealed room that is decoupled from the rest of the house.

len

TomM · Post by **TomM** » Tue Dec 27, 2005 11:50 pm

I was planning on using RC for the ceiling... but was just concerned about framing at this point. I have since learned it's better for isolation to not screw to the joists.

What kind of frame do you need to build to be able to support new floor joists with a few layers of drywall?

len-morgan · Post by **len-morgan** » Wed Dec 28, 2005 1:28 am

TomM wrote:What kind of frame do you need to build to be able to support new floor joists with a few layers of drywall?

It all depends on the span. And we need to get our terms correct: Floor joists would be the ones that are already there. Ceiling joists are what I'm proposing adding to sit on top of your new walls. That way, you will only have a connection through the floor and your sound proofing will be MUCH better.

Just for reference, I used single 2x8 on edge to cover an 8' span and doubled 2 x 8s (two 2x8s glued and nailed together for any spans longer than that. My longest span is about 15'. Also, I put them 24" OC. If you can mount them 16" OC you might be able to get away with single beams instead of doubling them up. And just to clarify, you want to have these new joists resting on top of your new walls and "standing up" between the current floor joists. That will maximize your ceiling height.

==========
After reading this, I forgot to answer the REAL question: You would use standard 2x4 studs (assuming you're using wood) with a bottom plate and two top plates. If you use pre-cut studs, you'll end up with just a shade under 8' for your ceiling after two layers of 5/8" dry wall.
==========

len

TomM · Post by **TomM** » Fri Dec 30, 2005 2:19 am

My span is 13 feet.... however, this probably can't be an option for me because my insulated heating ducts run through this room right on the one side. They go up through the ceiling too. So I wouldn't be able to support them on the other side of the frame. I want to box out the ducts....rather than lose that 3 feet of the room. DOH

len-morgan · Post by **len-morgan** » Fri Dec 30, 2005 7:00 am

Could the ducts be moved out far enough to get your new wall behind them? Then you could temporarily remove the duct, put up your new ceiling joists, and then put the duct back. You'd have to work a little harder at isolation (i.e., box in the duct as well as you would a normal wall), but it might still be workable.

len

Post by **Aaronw** » Fri Dec 30, 2005 8:35 am

Tom,

If you're trying to isolate from the structure of the joists above, you can try something similar to what I've done here...

http://www.johnlsayers.com/phpBB2/viewt ... &start=540

I left anywhere from 1/2" to 3/4" between the top plate and the joists (depends on the thickness of your brackets), which will dictate how much room to leave. Basically what I did is put down the bottom plate, measured from plate to joists, leaving the required gap, cut the studs for each end of the wall, slid the top plate on and attached the 2 studs, top plate and bottom plate together (leveled as well), then installed the rest of the studs.

Nashtalon · Post by **Nashtalon** » Sat Dec 31, 2005 6:54 am

knightfly wrote:It only takes about 1'4" gap to be able to tip a 2x4 stud wall into place after it's built on the floor

Am I missing something?

If the wall you've built on the floor is 97" and your joists are 99", why would you need a 1'4" gap to lift the wall into place?

Post by **sharward** » Sat Dec 31, 2005 7:04 am

Maybe that's supposed to be 1/4".

The / and ' keys are in very close proximity.

Nashtalon · Post by **Nashtalon** » Sat Dec 31, 2005 9:57 am

That must be it.

I can't see it taking (16) sixteen inches clearance to raise a wall.

knightfly · Post by **knightfly** » Sat Dec 31, 2005 9:38 pm

Sorry, stupid keyboard

- I went back and edited... Steve

(although, 1'4" would make it VERY easy to tip up your walls, even if they were a couple feet thick...

Post by **sharward** » Sun Jan 01, 2006 1:48 am

Yup -- and they'd be lighter, too!