Isolating walls from ceilings

[Finally]

When constructing normal walls, the 2X4's are are nailed or otherwiser directly attached to the ceiling. How do you isolated them from the ceiling to prevent sound from passing from the drywall to the 2X4's and on to the rest of the structurew?

[cadesignr]

Typical walls consist of a floor plate, studs and 2 top plates. Ceiling joists, and in the case of exterior walls, rafters too, rest on the top plates which structurally transfers the loads to the foundation. Sheetrock, or drywall is attatched to the ceiling joists.

Isolation walls can be built in a variety of configurations, depending on the overall design. Simple staggered walls sometimes are attatched to a floor common to both rooms, and MAY, depending on budget and other factors, actually support new ceiling joists, OR may simply be attatched to EXISTING ceiling joists, which are already supported by other walls.

It is how you decouple the drywall from the ceiling joists that is the trick. Resiliant Channel(RC) may be fastened to the ceiling joists, and then drywall fastened to the RC. However, RC must NEVER be fastened over existing drywall, as this will NOT provide enough airgap between leaves, will negate the use of RC and possibly create a three leaf system.

Another approach is for that of existing walls. RC may be used, but only if existing drywall is REMOVED, or large holes drilled exposing the wall cavity if insulation already exists. If not it is best to remove the existing drywall for insulation install.

Another method for the ceiling, depending on existing conditions of the structural elements, is to suspend it via Risc clips and metal hat channel. Multiple layers of drywall are screwed to the hatchannel which is suspended from the structure above via the risc clips and special wire. This method is more expensive than RC, and actually is suspended between walls. Takes much more skill and labor and materials may not be available to all locations.

Other options include isolating the walls on neoprene "U" boats, and new ceiling joists which actually means the walls and ceiling are "floating" as one unit decoupled from the rest of the structure. No other decoupling is necessary. Height restrictions may not allow for this, as in standard residential construction with existing ceilings. Unless they have higher than normal walls, or you don't mind less than standard floor to ceiling clearance. Span will determine nominal depth of new joists.

Last(as far as I know) would be a complete floating room within a room, which also can use either a wall supported ceiling structure, or a suspended ceiling between walls.

All of these methods have many many details to iron out before commencing construction. HVAC, door jambs, thresholds, trim, electrical and cabling are a few of the details that SHOULD be detailed or thought out in advance. Heavy doors require appropriate framing, changes in flooring materials or floor heights must be acounted for at the thresholds, HVAC registers and grills mounted to ducting and plenums must all be decoupled, electrical boxes offsets etc are but a few.

There is also a roll-out flooring material with built in neoprene pucks which after installation, plywood or osb subflooring is placed over, and then the finish floor. This type of flooring is installed between walls also.

Disclaimer: Everything I've said is subject to other members approval. ESPECIALLY Steve:lol: Just tryin to help with the workload Steve.
fitZ

Edit - Thanks Fitz, I space things for easier reading but you covered it just fine... Steve

[PhiloBeddoe]

Another option is to use sway braces. These are brackets that attach the new wall to either the existing ceiling or another parallel adjacent wall usually using some combination of rubber and springs, thereby decoupling them from the structure.

See Kinetics Noise Control and Mason Industries for example.