Attaching resilient channel to old concrete ceiling

Posted: Sat Jun 07, 2008 4:59 pm

I have decided I need to cover the vaulted ceiling in my basement space

(thread with photo here http://www.recording.org/ftopict-47059.html)

with plasterboard on resilient channel. Not wanting to lose any height, I was hoping to screw the resilient channel directly to the hard ceiling with rawl plugs. I have noticed on the net though a few photos/diagrams showing 50mm wooden battens fixed to the existing ceiling and then the resilient channel screwed to this. (Although the ceilings shown are never hard they are always wooden beams with plasterboard).

My question is: are these battens purely for structural pruposes or in your view am I likely to gain any additional noise reduction effect by employing them?

Posted: Sat Jun 07, 2008 6:28 pm

The answer is both..........

Added Air space increases isolation.

Remember - the A in MAM stands for Air.

I do not like your idea with the rawl plugs........ they really are not designed to take that sort of loading forever.

Check with a local supplier of products from HILTI - and obtain either steel inserts designed to handle the straight pullout loading - or use chemical anchors (epoxy) to permanately attach threaded rod to carry the 50mm members.

Sincerely,

Rod

Rod

Posted: Sun Jun 08, 2008 3:00 am

Rod Gervais wrote:

The answer is both..........

Added Air space increases isolation.

Remember - the A in MAM stands for Air.

Thanks Rod. I didn't consider the air space factor. Another question:

Would there be any decoupling effect from fixing the res bars into these wooden battens as opposed to directly into the concrete ceiling? If not I will fix the res bars to the lowest part of each vault which is 50mm lower than each apex. Not a uniform airgap but better than nothing.

Quote:

I do not like your idea with the rawl plugs........ they really are not designed to take that sort of loading forever.

I see your point. I already have some metal threaded fixers which, when you push them into a hole in cement and screw in a length of threaded bar, become locked in place. I think they might be similar to what you are referring to.

Posted: Sun Jun 08, 2008 6:51 am

Driller wrote:

Would there be any decoupling effect from fixing the res bars into these wooden battens as opposed to directly into the concrete ceiling? If not I will fix the res bars to the lowest part of each vault which is 50mm lower than each apex. Not a uniform airgap but better than nothing.

Yes there is an added efect that takes place, picture that the decoupling take place trough 2 processes - the first is the design of the channel itself - the holes (or slots as the case may be) decrease tremendously the amount of energy passsing through the channel into the assembly.

However - there is a 2nd part to this - and that is the fact that the channel itself is decigned to come into very small contact with the assembly as well.

It is designed to be connected at very small spots - 1 1/2" wide (basically) so that this is the only area energy can be structurally transmitted through.

You defeat that part of the equation by installing it dirctly to a full surface.

Quote:

I see your point. I already have some metal threaded fixers which, when you push them into a hole in cement and screw in a length of threaded bar, become locked in place. I think they might be similar to what you are referring to.

Regardless of what you might think - what you need to do is to determine exactly where you are going to place them - which will let you calculate exactly what your total loading per fastener is - and then verify that they are designed to take that loading.

When it comes to things like ceilings this is absolutely critical - because a person could be killed if one of these were to collapse on them - and when it does happen there generally is no warning at all. One second it's up - the next it's on the floor.

and with these fasteners it is not only a question of will it lock into place - it is also what the depth is of the connection - taking into account the shear of the concrete. All carefully designed to have safety factors in play.

So do not just assume they are adequate - if you cannot positively identify them - then don't use them - buy new ones that are designed for the task at hand.

Sincerely,

Rod

Posted: Sun Jun 08, 2008 3:37 pm

Rod Gervais wrote:

Yes there is an added efect that takes place, picture that the decoupling take place trough 2 processes - the first is the design of the channel itself - the holes (or slots as the case may be) decrease tremendously the amount of energy passsing through the channel into the assembly.

However - there is a 2nd part to this - and that is the fact that the channel itself is decigned to come into very small contact with the assembly as well.

It is designed to be connected at very small spots - 1 1/2" wide (basically) so that this is the only area energy can be structurally transmitted through.

You defeat that part of the equation by installing it dirctly to a full surface.

Right, something else I just learned. What about then if I used some sort of rubber bush like a thick washer or some proprietary rubberised isolation material under the res bar at the fixation points?

Quote:

Regardless of what you might think...

Agreed, that wasn't very scientific of me

Quote:

- what you need to do is to determine exactly where you are going to place them - which will let you calculate exactly what your total loading per fastener is - and then verify that they are designed to take that loading.

When it comes to things like ceilings this is absolutely critical - because a person could be killed if one of these were to collapse on them - and when it does happen there generally is no warning at all. One second it's up - the next it's on the floor.

and with these fasteners it is not only a question of will it lock into place - it is also what the depth is of the connection - taking into account the shear of the concrete. All carefully designed to have safety factors in play.

So do not just assume they are adequate - if you cannot positively identify them - then don't use them - buy new ones that are designed for the task at hand.

Sincerely,

Rod

Your comments here are most appreciated thank you. You've given me a bit of a fright actually-and probably a good thing too! I shall study this side of things in depth and speak to a professional.

I did wonder though: the walls of the basement are 40cm thick stone with plaster on the internal face. I was hoping to leave this alone and just isolate the ceiling. I did a test you see and my Marshall is very noticable in the kitchen above. I'm starting to wonder if I'm going to need to do something to the walls and if the exact same method would be sufficient to stop structure born noise?

I will do a test after I get the ceiling up. Obviously at that point a room in a room will be too late.

Sorry to have rambled on.

Posted: Sun Jun 08, 2008 8:01 pm

You shouldn't waste time and money on the ceiling if you are not planing on isolating the rest of the room.

Flanking through the walls will defeat anything you do on the ceiling alone.

Remember - your weakest points become your biggest transmitters. Tiy cabbit create isolation by attacking one piece of a room - it has to be the whole room or it just doesn't work.

So either isolate the whole room - or save your dollars and live with it like it is.......... please listen to what I am saying - do not throw away good money when you don't have to.

Sincerely,

Rod

Posted: Mon Jun 09, 2008 5:37 am

Rod Gervais wrote:

You shouldn't waste time and money on the ceiling if you are not planing on isolating the rest of the room.

Flanking through the walls will defeat anything you do on the ceiling alone.

Remember - your weakest points become your biggest transmitters. Tiy cabbit create isolation by attacking one piece of a room - it has to be the whole room or it just doesn't work.

So either isolate the whole room - or save your dollars and live with it like it is.......... please listen to what I am saying - do not throw away good money when you don't have to.

Sincerely,

Rod

I hear what you're saying Rod. OK so I'll do the walls too: studs and resilient channel, since now I know I must not apply the res channel directly to the wall Wink

Thanks for your help in this.

Posted: Mon Jun 09, 2008 6:58 am

If you do a seperate wall - then you do not need (or even want) the resilient channel.

Use 2x6 construction @ 2'- 0" om cemter (the same board feet of lumber as 2x4 16" o.c.) without resilient channel and you get your maximum low frequency isolation.

Resilient channel on that wall will lower your LF TL values - not raise them.

Rod

Posted: Tue Jun 10, 2008 3:50 am

Rod Gervais wrote:

If you do a seperate wall - then you do not need (or even want) the resilient channel.

Use 2x6 construction @ 2'- 0" om cemter (the same board feet of lumber as 2x4 16" o.c.) without resilient channel and you get your maximum low frequency isolation.

Resilient channel on that wall will lower your LF TL values - not raise them.

Rod

Rod, last two questions-

1) Are the studs of this new wall fixed to the existing stone one or just sitting between the floor (on an absorbant material of course, sheetblock etc) and fixed to the lowered ceiling? If not fixed to the wall, what's the minimum distance between the joists and the stone wall?

2)Is this all in your book?

Posted: Tue Jun 10, 2008 4:11 am

It's all in the book.

You don't need anything special on the floor -

use isolation braces to hold it off the wall at the top - then you don't worry about flanking.

keep it at least 1" off the existing wall

Rod

Posted: Tue Jun 10, 2008 11:51 am

Rod, thanks for all your help in this. I'm going to go away for a while as I have some reading to do Thumbs Up

Posted: Thu Jun 19, 2008 5:28 am

Rod, excellent book and easy to understand. Thank you for making this information available.

On page 59 you mention RSIC clips. I have found a French version of these:

Do these look like the same thing to you and for my situation can you confirm that they would be a good idea fixed to threaded rod from the concrete ceiling with hat channel below? They are not cheap (it will cost me €250 Euros for 40 but if they work then I'm all for it).

I think obviously "yes" but then again I was ready to put resilient channel on my walls...

Posted: Thu Jun 19, 2008 7:04 am

Driller,

I don't know - just looking at that clip - I don't see how in the world a hat channel would attach to it.

Picture a hat channel - from the side it looks like a hat - yet this clip would require the hat's "brim" to fold in not out.

AndI have never seen a hat channel like that.

I would like a link to the website so I can see this for myself.

Rod

Posted: Thu Jun 19, 2008 8:41 am

Sorry Rod, I used the term "hat channel" to communicate in US terms. Over here the metal "Rails" system is as you descibed with the brim folded in thus:

The page for the clips is here, all in French I'm afraid.

http://www.placo.fr/bpb_fr/ProduitsOuvrages/catalog/sproduit.aspx?ProductID=H88290000

Equally, deviding walls are built here using a light weight 25 gauge (0.5mm) metal stud system which I shall be using for doubling the walls.

I was happy to see you mention in your book that this gives superior isolation to a wooden system.

In the book you talk about doubling walls first then adding the ceiling up to the walls. If I dropped the ceiling first up to the existing walls (1/4" caulked gap) and then doubled the walls to this, would this make a difference? Which is the better way?

regards
D

Posted: Thu Jun 19, 2008 11:08 am

Re-read what I said in the book - which was that light guage metal framing was equal to a single stud wall with resilient channel.

When I stated that it was superior to wood (or heavy steel framing) I carefully noted that this was in comparison to a simple stud wall - not a dual wall assembly.

Light guage steel studs (in a dual wall assembly) will NOT give you as high TL values in the lower frequency range as you will acheive with heavy guage metal or with wood.

That is the disadvantage of the light guage steel framing.

Sincerely,

Rod

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