Flanking noise when treating common party wall.

[johnp]

Sarah

fyi - You can also try RPG Europe ( http://www.rpg-europe.co.uk/ ) as a supplier of Green Glue, if you need it.
The quote i got (October 2007!) was £9 per tube.

rgds

[Sarah E]

Hi all.

Got almost everything I need to start the actual works but just have a questions about the Plasterboard/Gyproc.

I intend to use two layers of 12.5mm Plasterboard (+greenglue in-between) for the wall, but should I use two layers of 9.5mm or 12.5mm plasterboard for my ceiling application?

More mass seems to be a key factor in reduction, but I am worried about the whether the Isomax clips will be okay to hold the weight 2 layers of plasterboard. Each clip is rated at 22.5kg, and I will be using approx 30 clips on the ceiling joists.

Also, should I be using self-tapping screws when fixing the boards to the channel, or will normal plasterboard screws (for wood frames) be okay ?

Thanks very much,
Sarah.

[rod gervais]

I intend to use two layers of 12.5mm Plasterboard (+greenglue in-between) for the wall, but should I use two layers of 9.5mm or 12.5mm plasterboard for my ceiling application?

Sarah,

your best bet would be 2 layers of 16mm (in both locations)- under no condition would I use less than he 12.5 mm if I were you.

More mass seems to be a key factor in reduction, but I am worried about the whether the Isomax clips will be okay to hold the weight 2 layers of plasterboard. Each clip is rated at 22.5kg, and I will be using approx 30 clips on the ceiling joists.

Isomax CLips will handle that load and more without any issue.

Also, should I be using self-tapping screws when fixing the boards to the channel, or will normal plasterboard screws (for wood frames) be okay ?

You need to use a self tapping, bugle head drywall screw for metal frame applications.

Rod

[Sarah E]

Thanks Rod, and everyone, for you kind replies.

Hi Rod, I have no experience in construction, and I am naturally concerned about the weight of 2 layers of 12.5mm plasterboard, plus a coating of finishing plaster, hanging above my bed. Can you, or anyone, put my worries to rest and help me with these questions ?

1. I shall screw the Isomax clips into the Ceiling joists using two wood screws per clip. The joists are 100mm deep, so if the screw goes into the wood approx 50mm, will that be enough?

2. The first layer of 12.5mm plasterboard is screwed into the Hat-Channel using 38mm screws. The second layer of 12.5mm is ALSO screwed into the Hat-Channel, but using longer screws (65mm) that go straight through the first layer of plasterboard. Am I using the right length of screws or are they too long really (38mm + 65mm)?

3. Rod said to use self-tapping. Is this the same as Self-Drilling that I have found below? There seems to be a choice of Fine or Course screws too. I don’t know which ones to use? I read somewhere that the self-drilling ones can tear up the channel and that Fine screws were the ones to use on Hat-Channel or have I miss-understood?
http://www.screwfix.com/prods/27940/Scr ... ck-of-1000
http://www.screwfix.com/cats/A331389/Sc ... all-Screws

4. Will the Clips and Channel definitely hold two layers of 12.5mm Plasterboard and a 3mm coating of finishing plaster ?

I respect Rod as he is an expert but I cant help but worry -

Thanks so much for your kind words of help!
Sarah

[Soundman2020]

Hi Sarah,

If Rod says it will work, then it will work.

Just one note of caution: Be very careful with your plasterboard screws to make sure that none of them go into the joists! That would "short circuit" the clips entirely, making all your hard work for nothing. You need to make absolutely certain that your screws go ONLY into hat channel, and don't come near the joists. Since you wont be able to see where the joists are accurately once you have the plasterboard in place, and especially for the second layer when you can't see them at all, you need to mark the positions of the joists and the hat channel on your WALLS, right below the ceiling. You can even snap chalk lines across the plasterboard if you need to, to make it easier to know exactly where the joists and hat channel are.

Ditto for your wall.

- Stuart -

[rod gervais]

1. I shall screw the Isomax clips into the Ceiling joists using two wood screws per clip. The joists are 100mm deep, so if the screw goes into the wood approx 50mm, will that be enough?

Isomax requires #8 x 2.5" coarse screw. That would be a 65mm screw.

2. The first layer of 12.5mm plasterboard is screwed into the Hat-Channel using 38mm screws. The second layer of 12.5mm is ALSO screwed into the Hat-Channel, but using longer screws (65mm) that go straight through the first layer of plasterboard. Am I using the right length of screws or are they too long really (38mm + 65mm)?

USG requires at least 5/8" of penetration (16mm) so for 5/8" drywall (instead of your 1/2") it woud be 32mm and then an additional 14 mm for the 2nd course or a total of 48 mm....... your 2nd layer screw is WAY too long....

3. Rod said to use self-tapping. Is this the same as Self-Drilling that I have found below? There seems to be a choice of Fine or Course screws too. I don’t know which ones to use? I read somewhere that the self-drilling ones can tear up the channel and that Fine screws were the ones to use on Hat-Channel or have I miss-understood?
http://www.screwfix.com/prods/27940/Scr ... ck-of-1000
http://www.screwfix.com/cats/A331389/Sc ... all-Screws

There is a difference between drywall screws for wood and drywall screws for metal.

In the States a drywall screw for metal would be a Buglehead type S - for wood it is a type W - so you want an S type screw - and that will have a fine thread - you never use a coarse thread on a steel stud.

4. Will the Clips and Channel definitely hold two layers of 12.5mm Plasterboard and a 3mm coating of finishing plaster ?

2 layers of 16 mm drywall (which i really what you should use) weight roughly 10 pounds per square foot - and 3mm of finishing plaster weights .21 pounds....... that's a total of 10.21 pounds per square foot.

According to Isomax:

Load Specification for IsoMax Clips

The IsoMax clip is designed to carry a drywall furring channel (hat track) with one or more layers of gypsum wallboard
attached. THE LOAD CAPACITY OF THE CLIP DEPENDS ON THE GAGE OF FURRING CHANNEL USED.

Lighter, 25 ga, furring channel carries less load than 22 ga channel. The maximum design load capacity for the
IsoMax clip in shear (wall application) or in tension (ceiling application) is as follows. Design load calculations are
based on tested loading to failure where the furring channel deforms and pulls out.

Design Load Maximum for Wall or Ceiling Application
................................................................ 2:1 safety factor....... 2.5:1 safety factor*
IsoMax clip with 25 ga steel furring channel.............. 45 lbs......................... 36 lbs.
IsoMax clip with 22 ga steel furring channel.............. 60 lbs......................... 48 lbs.

Note: 5/8" thick gypsum wallboard weighs 2.3 lbs/sq ft. 1/2" thick gypsum wallboard weighs 1.85 lbs/sq ft.
* Suggested safety factor of 2.5:1 for more critical life safety applications; i.e., hospitals

Thus the manufacturer rates these for a 90 pound per square foot load with 25 ga hat section) - and our total load of 10.21 is working with a safety factor of 8.9:1............ (they consider 2.5:1 to be adaquate for hospitals........ we beat that by more than 3 times the safety factor.

I respect Rod as he is an expert but I cant help but worry -

Understandable to be cautious.

I hope this helped.

Rod

[rod gervais]

Just one note of caution: Be very careful with your plasterboard screws to make sure that none of them go into the joists! That would "short circuit" the clips entirely, making all your hard work for nothing. You need to make absolutely certain that your screws go ONLY into hat channel, and don't come near the joists. Since you wont be able to see where the joists are accurately once you have the plasterboard in place, and especially for the second layer when you can't see them at all, you need to mark the positions of the joists and the hat channel on your WALLS, right below the ceiling. You can even snap chalk lines across the plasterboard if you need to, to make it easier to know exactly where the joists and hat channel are.

Stuart,

Actually - although this is true with both RC-1 and RC-2 - it is impossible to hit a stud using the RSIC clips and the right length screws

First off - the clip itself protects the stud.......

Next - it is 1 1/8" from the face of stud to the back of drywall - and you only need 5/8" penetration of the metal for the screw.

This is a foolproof system.

Rod

[Soundman2020]

Thanks Rod! You live and you learn! And once again I'm confusing RC with RSIC clips! Sigh!

- Stuart -

[Sarah E]

Hi everyone,

So, the original plasterboard was removed from the existing ceiling to expose the joists, and then the Isomax clips were screwed to these joists and horizontally across the party wall. You cant get 5/8 plasterboard from the local builders yards in UK ( or so it seemed to me) so I settled for two layers of 12.5mm thickness ( sorry Rod )

The first later was screwed in, at 150mm intervals. Once both the new wall and ceiling were up, the gaps between the edges of the boards were filled with a plasterboard filler (mud??) and then sanded smooth so there were no protruding bits. A second layer was then installed over the first, with a tube of GG being used on each 8x4 sheet. The joins in the first layer did not co-incide with any joins in the second layer. Great care was taken that the screws used on the second layer did not hit any used in the first layer. Also, as per Rods recommendations for screw length, the screws could not have short circuited against the original wall.

1) The existing walls were not totally square and the plaster on the walls was quite bumpy, so the gap left between the new plasterboard and the original walls/floor etc varies from 3mm-14mm, I hope this is okay ?

2) The gaps now need to be filled with Acoustic Caulk. I cant seem to find Backer-rod ( Caulk-saver) so am I okay just to squirt loads of Caulk into the gap until it fills up ?

3) I hope I have done everything correctly. Can anyone see if I have made any mistakes in my description above? The noise from neighbour is no different, but I'm guessing that's because I have not caulked the edges yet and so the new wall is not air-tight?


Thanks, Sarah.

[rod gervais]

Sarah,

you said new walls - so you did those before putting up the ceiling?

You really need backer rod otherwise the odds are greatly against you when it comes to the caulk failing. I find it hard to believe that no one carries it.

have you already caulked the perimiter of the walls as well?

In a room - all 12 edges need to be caulked / sealed in order for the room to seal.

Rod

[Sarah E]

Hi Rod. Sorry for being confusing.


I put clips+channel on the ceiling joists and on the common party wall. On these I hung 2 layers of Gyproc.

The new Gyproc on the ceiling stops short of all four existing walls by approx 10mm.

The new Gyproc on the wall stops short of the existing side walls and the floor, but it now touches the new ceiling.


So basically the new Gyproc on both the wall and the ceiling touches nothing but each other. Where the new wall meets the new ceiling, I have filled with filler.

I haven't caulked any of the edges yet.

[xSpace]

Sarah E, I am curious how this is turning out. Have you guys reached a satisfactory noise reduction yet or is it still in an on going status?


Thanks,

Brien

[Soundman2020]

Sarah, it's a couple of years later and I'm just wondering how this worked out for you in the end, after sealing? It's an interesting thread, and could be very useful to others in your same situation.

- Stuart -

[Zenon Marko]

Just one note of caution: Be very careful with your plasterboard screws to make sure that none of them go into the joists! That would "short circuit" the clips entirely, making all your hard work for nothing. You need to make absolutely certain that your screws go ONLY into hat channel, and don't come near the joists...

- Stuart -

Hello, everyone -
So short screws will avoid the risk of driving them into the joists. Is there a problem if the screws through the drywall touch the actual (RSIC or other) clip itself, such as the washer on top of the RSIC clip?

Thank you for any advice...I couldn't find this info on any of the clip manufacturer sites.

[Soundman2020]

Depends what part of the clip it touches! If it touches the part that the hat channel clips into, then no problem, but if it touches the rubber or the part that screws into the stud, then you have the same problem. This is why it's so important to measure very carefully, and transfer the locations of studs, clips, wiring, HVAC ducts, etc. onto the floor or ceiling, and the drywall as it goes up, so you don't make mistakes.


- Stuart -