I'm the proud dad of 11-year-old twin boys. Unfortunately, their bedroom is right above the dining room and when they jump from their bunks the whole ceiling shakes and booms.
As part of a renovation project I will have the DR ceiling open and will have access to the joists. What could I do to stiffen the floor above and silence some of the noise? (I'm thinking ahead to the boombox days coming soon, too.)
The DR is 12x16 with 2x10 joists running the long way, 16" o.c. Would adding more blocking or sistering the joists with 2x?s work, and which would be better? What about insulation? I'd like to do this as cheaply as possible (of course!)
Addressing only the noise, I recall reading a magazine article about soundproofing some years back. If my memory is accurate, a builder was attaching drywall to the studs using some sort of clips. The clips didn't actually attach the drywall, but isolated it somewhat from the studs. Sorry if this is vague, but I think I'm on the right track. You might want to consult some library books. It can't be that tricky.
As far as the bouncing, be glad they are normal kids who can walk and crash into things. Grab the Jack Daniel's every so often. It makes the noises of kids much funnier. When the noise stops, that's when you start worrying.
Notch 16' 2x6s at the ends, so that they ride 1/2" to 1" lower on the bottom edge than the existing joists, and set them between the existing joists, so that the ceiling of the room below is independant of the floor of the room above. If there's blocking in the existing floor that prevents this, then use resiliant channel, and one layer of homasote 440 soundboard covered by regular sheetrock. Insulation won't help with low-frequency noise and vibration. Seal any air gaps. Put an area rug in the bedroom.
Install 2x10 "sisters" about 12 feet long centered on the existing joists. It would be best to rip about 1/4-inch off the sisters. That way they are not full depth and the floor sheathing won't rub & squeak. Align with the bottom of existing joists and glue & screw w/ 2 rows of #9x2-1/2" deck screws @ 12" o/c.
A. Sistering the joists 1 for 1 will only double the strength of the floor. The deflection will be approximately 1/2 of previous. Installing that many joists involves high material costs, difficulty in fitting the additional joists, and the considerable labor.
B. Adding three rows of [1X5] "X" bridging, say nailed, at approximately
4 ft. centers, can considerably reduce the deflections of individual joists by transferring their loads to the adjacent joists.
C. The reduction of deflection can better than 1/4 of the previous if,
1, sistering is not done, and, 2, you add a substantial tension member to the lower chord (or bottom edge) of the joists. Consider placing a continuous 16 ft. long [2x6] under each joist and the full length of the joist. Use screws and Gorilla glue to bond the horizontal sides of the
2Xs (layed flat and not vertical) so that no longitudinal slippage (or shear) between the joists and the added pieces can occur. Use extra screws at each end. The screws don't do the work in shear; the glue does the work, and the screws merely clamp the glued 2Xs. Drilling pilot holes for the flat head wood screws screws is best. On advice regarding the right type of nail, power driven nails may also work. I would add 3 or 4 screws at the ends of the joists where the shear forces are greatest. This scheme will lower the neutral axis of each joist and give you less deflection, less cost, and easier installation.
I suggest using schemes B & C.
Use acoustic caulking at all openings, near the walls and beneath the baseboards of the room above. A new GWB ceiling would be necessary. To increase the acoustic mass of the ceiling and to reduce the acoustic vibrations, install 2 layers of 1/2 or 5/8 in. GWB.
Increasing the stiffness will decrease the deflections, but won't do much to reduce the sound.
There's nothing in Ralph's suggestions that will isolate the sound (other than the use of acoustic caulking). Increasing the mass and the stiffness simultaneously may have no noticable effect.
If you don't mind losing a bit of headroom, I'd try running a set of joists independent of the existing joists. They only have to be stiff enough to support the ceiling. The tricky bit will be to brace the new joists. You could probably use 2x6 across the short span, but that would drop your ceiling by about 8" or more by the time you're done.
If you decouple the floor and the ceiling, then the jumping and noise will not transmit as much. Use resilient channel to suspend a double thickness of GWB from the new joists. This will reduce the stiffness and increase the mass of the ceiling - key to reducing noise and vibration transmission. Make sure that the new ceiling is lower than the old joists by as much deflection as you'd reasonably expect. Then the floor can bounce independent of the ceiling. You could try adding acoustic insulation to the underside of the floor as well. Definitely caulk.
At a bare minimum, resilient channel on the existing joists supporting a thick ceiling with acoustic insulation and caulking would help. No stiffening required.
Personally, I thought they invented basements for noisy kids.
Seriously, how about correcting the behavior just like my parents did and I did with my children. If you are proud of them teach them to be civilized. Tell your children that you don't want them to do that. The same applies to the "boombox days", "children, boomboxes are rude and annoying and we will not have them in this house and it is just as inconsiderate and rude if you use them elsewhere...".
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