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Isolation: Wall structure stability
Old 22nd April 2015
  #1
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Lightbulb Isolation: Wall structure stability

Hi Guys!

Guess I need your help this time, construction wise.

I´m helping an old friend. He´s a family guy, and wants to use a spare room to rehearse with his loud rock band trio, and occasionally record some stuff too. This room is right next to the house, obviously constructed over the same concrete slab. But while rehearsing / recording he really needs good sound isolation, so as not to bother wife and kids at all.

I came with a design based on the Recording Studio Design book, by P. Newell.
This is the empty room. (roughly 5m (L) x 3.5 (W) x 2.8 (H)

IMAGE 1 - Empty Room (first attached image)
IMAGE 2 - Proposed Isolation (Second attached image)

I´m going for the "a room in a room" concept. The new interior walls will be sand-filled, hollow concrete blocks, mechanically decoupled from the original floor slab, by means of floating it. The ceiling will be supported by new walls (gypsum boards, nailed to wood beams attached to this new walls)

So it all boils down to ONE QUESTION.
- In a set up like the one I´m trying to build, do the walls need some type of anchorage (by means of decoupling clips, frame channels, etc.)?
- Will they maintain the structure just by being constructed over the floating spring (plywood and fiberglass base)?

I would really appreciate some help with this matter. I´m really concerned about safety. And although the owner of the house works full time as a master builder, we are quite doubtful regarding this subject.

Thanks a million..
Cheers!
Spacefolder
Attached Thumbnails
Isolation: Wall structure stability-altamira-sketchup-01-outer-shell-big.jpg   Isolation: Wall structure stability-altamira-sketchup-03-isolation-big.jpg   Isolation: Wall structure stability-altamira-sketchup-04-beams.jpg   Isolation: Wall structure stability-altamira-sketchup-05-cross-section-ceiling-detail-n1.jpg  

Last edited by spacefolder; 26th May 2015 at 01:18 AM.. Reason: Added attachments
Old 22nd April 2015
  #2
Gear Nut
 

Quote:
Originally Posted by spacefolder View Post
Hi Guys!

Guess I need your help this time, construction wise.

I´m helping an old friend. He´s a family guy, and wants to use a spare room to rehearse with his loud rock band trio, and occasionally record some stuff too. This room is right next to the house, obviously constructed over the same concrete slab. But while rehearsing / recording he really needs good sound isolation, so as not to bother wife and kids at all.

I came with a design based on the Recording Studio Design book, by P. Newell.
This is the empty room. (roughly 5m (L) x 3.5 (W) x 2.8 (H)

IMAGE 1 - Empty Room (first attached image)
IMAGE 2 - Proposed Isolation (Second attached image)

I´m going for the "a room in a room" concept. The new interior walls will be sand-filled, hollow concrete blocks, mechanically decoupled from the original floor slab, by means of floating it. The ceiling will be supported by new walls (gypsum boards, nailed to wood beams attached to this new walls)

So it all boils down to ONE QUESTION.
- In a set up like the one I´m trying to build, do the walls need some type of anchorage (by means of decoupling clips, frame channels, etc.)?
- Will they maintain the structure just by being constructed over the floating spring (plywood and fiberglass base)?

I would really appreciate some help with this matter. I´m really concerned about safety. And although the owner of the house works full time as a master builder, we are quite doubtful regarding this subject.

Thanks a million..
Cheers!
Spacefolder
Hello,
I think the biggest safety issue here is the roof/ceiling.
I did a quick check on your beams/joists (150x50). They can't handle the load from 60mm of gypsum board, even at 600mm spacing.
Something to consider.
You wrote that the floor slab is connected with the main house, but is the concrete slab in the ceiling also connected?
/Gustav

Last edited by gustav82; 24th April 2015 at 08:59 AM.. Reason: a little too much info
Old 22nd April 2015
  #3
Gear Nut
 

I was a little hasty in my last post.
Of course you should place your joists along the shortest wall, so the span is 3,5 meters. Your drawings suggested otherwise, although I'm sure you would do it that way.
However you should use at least 600mm spacing between the joists.
/Gustav
Old 22nd April 2015
  #4
Gear Maniac
 

Hi - I"m sure someone more knowledgeable than me (Rod, John etc?) will chip in but to me that's not a good way to 'float' the walls off the slab. In practice the fibreglass will just compress and couple your walls to your floor!

I'd just build on the slab direct and decouple the floor within. Also I'd just build with dense concrete block rather than fill with sand - less hassle.

I would also not bother with the barrier mat on the ceiling.

Don't forget fresh air in/out and cooling etc etc

J
Old 22nd April 2015
  #5
Gear Nut
 

As for the stability issue, that you're concerned of. I see no problems with it.
Think of it as if it would be a free standing house, without the existing walls. Would it be stable then? As long as you glue/put mortar between the blocks and you have 4 walls that are connected, it shouldn't be an issue.
Good luck with the build!
/Gustav
Old 22nd April 2015
  #6
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Thanks Gustav & Jon!

Basically, everything is attached to the house. The original concrete floor slab is shared with the house, so as the concrete ceiling and the "left" wall, which has the living room on the other side. Thats why I think it's very important to float and decouple everything.

Gustav, yes, the beams WILL be on the shortest span of 3.5m.
My mistake while drawing :p

UPDATED IMAGE
3rd attachment (ALTAMIRA sketchup 04 beams.jpg)


Jon,
1) You are suggesting me to remove the vinyl barrier from the ceiling. Why?
So as not to load so much weight to the beams, or because you think it's not worth the bang for the buck ratio?
I was trying to gain some mass, so as to match the walls and at the same time create a Constrained Layer Damping by sandwiching the viscoelastic barrier. Not worth? (Walls are 140Kg/m2, while ceiling is just 60Kg/m2).

2) Thanks for the tip about the sand-filling hassle! I guess I could use regular solid bricks, plastered on the side facing the room.

3) You are suggesting me not to "float" the inner walls..
What about decoupling. Loud rock inside, haha. I believe, airborne sound will in fact "flank" to the slab, including wall resonances. Wouldn't 160 Kg/m3 rigid fiberglass, spread along the entire wall do the job, as suggested by P. Newell?

Thanks a billion guys!
Old 23rd April 2015
  #7
Gear Maniac
 

Hi in answer to your questions:

1) goes it's expensive and cheaper drywall will do the same thing IMHO

3) I'm not an expert but I can't see how you can truly float the whole structure (walls & ceiling) this way. I'd also be worried about settling over time as the weight compressing the insulation.
Old 23rd April 2015
  #8
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In my mind this boils down to a whole lot more than 1 question.........

First (and foremost) your floating wall system won't work...... I am not saying "it may not work" - but rather "it won't work."

You cannot float a masonry wall on that material - eventually the wall will fully compress the insulation and at that point nothing is structurally decoupled/isolated......

If you are bound and determined to do this (personally I would not bother trying to float those walls) then the isolation system needs to be properly designed not only from the perspective of selecting a proper product as the base material - but also the total loads that are going to bear on it..... you will have greater loads on the bearing walls than the non bearing walls.

With masonry structure you may well be close enough that this ends up a one size fits all, but only a very careful analysis will tell whether that is the case or not.

I tell you this because I have designed floating rooms - and in one particular case the design required 7 different isolators (from the perspective of load bearing capacity although all were the same thickness) to properly isolate the building....

If all you plan on doing is to simply build on top of something (just to feel good about things) then you are pretty much wasting your time.

Now - I would also be concerned about how all of this is being braced laterally......... the bottom of wall needs to be locked into place as does the top of wall (and possibly the center of the wall depending on wall height.) This can be done either through the use of properly sized lateral sway braces, or by developing a wall reinforcement design using grouted cores with rebar.....

The top of the masonry wall should utilize a reinforced bond beam.

You should also pay close attention to the means by which the ceiling frame is attached to the face of that masonry wall....... based on your design concept you are going to have to focus on/deal with shear conditions with the fasteners you use at the continuous plate you need to carry those joist (unless your plan is to let them into the masonry - however that is not an approach I would recommend.) If you are not letting them in then your detail is missing the very important continuous member that these joist are going to be attached to in the inside face of that masonry wall.

Assuming a plate attached to the wall you need a fastening system designed for attaching that member to the masonry - and then joist hangers to attach the ceiling joist to that plate.

Regardless of which system you use you also need to provide mid span bracing for those ceiling joist to avoid issues (in the long term) with the center of the joist rotating under load.

Outside of that........ you indicate that you want to bond all of those sheets of drywall together on the ceiling...... which will decrease your isolation (especially in the lower frequency range.) Save your cash and lose the idea of turning this into 1 thick sheet at that location.

You are also spending a bunch of cash on mass loaded vinyl sandwiched in between layers of drywall - which is pretty much simply a waste of money to save a tiny bit of space....

Once you lock that mass between layers of drywall it's only value is the mass......... and the cost is huge compared to what you could gain by simply losing the MLV and adding another layer of drywall.

Best of luck,

Rod

Last edited by Rod Gervais; 23rd April 2015 at 07:19 PM..
Old 23rd April 2015
  #9
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+1!
Old 23rd April 2015
  #10
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An after thought here......... you are using a 4" masonry block - the block will definitely require lateral bracing in the body of the wall - and probably more than just mid height..... sorry I missed that........

Rod
Old 23rd April 2015
  #11
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By the way - just so there is no misunderstanding......... Phillip Newell is very sharp...... so my best guess is that you are not understanding something he laid out in his book...

1 linear foot of standard weight 4" hollow core concrete block weighs in around 34.5 lbs....... what you've drawn is slightly over 11 blocks tall....... that puts the block load (just the block load) at roughly 386 lbs per linear foot.......

You have the bearing pad drawn the same width as the block...... so 4" in width...... that means that for every linear foot of wall the load is being supported by .33 sf of pad.....

The compressive strength of 705 is around 200 psf @ 10% deformation that means the pad is capable of about 67 plf @ 10% deformation once you cut it down to the 4" wall width you show in your sketch......... so it's overloaded by about 133 plf before we begin think about sand inside the cavities, plus the ceiling load - and the weight of the rendering on the face of the block.

The math just doesn't work for me here.........

Rod
Old 24th April 2015 | Show parent
  #12
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Quote:
Originally Posted by Rod Gervais View Post
By the way - just so there is no misunderstanding......... Phillip Newell is very sharp...... so my best guess is that you are not understanding something he laid out in his book...

1 linear foot of standard weight 4" hollow core concrete block weighs in around 34.5 lbs....... what you've drawn is slightly over 11 blocks tall....... that puts the block load (just the block load) at roughly 386 lbs per linear foot.......

You have the bearing pad drawn the same width as the block...... so 4" in width...... that means that for every linear foot of wall the load is being supported by .33 sf of pad.....

The compressive strength of 705 is around 200 psf @ 10% deformation that means the pad is capable of about 67 plf @ 10% deformation once you cut it down to the 4" wall width you show in your sketch......... so it's overloaded by about 133 plf before we begin think about sand inside the cavities, plus the ceiling load - and the weight of the rendering on the face of the block.

The math just doesn't work for me here.........

Rod
+1
On the sketch it first looked like you had pretty wide blocks, although they are only 10cm. So I agree with Rod that you should use lateral bracing or "wall ties" or whatever it is called. A little lost in translation here
Also I would have put the concrete slab all the way under the walls, with the slab thicker in the edges (and with reinforcement bars). That way you should be able to distribute the pressure from the wall. Make sure though that you use ground insulation here, that can handle enough pressure.

But as mentioned before, maybe you should try some other solution. Maybe with a simple extra drywall (with x number of layers and 2x4 studs for instance), decoupled from the existing wall. This "light" wall could be standing on a wood chip board (floor type, with joints that you glue), and a thin layer of very rigid insulation under that. Also you should use a vapour barrier beneath, protecting the wood from the concrete slab (which can get moisty from time to time).

A lot cheaper/easier, maybe not perfect. But I did something similar, and it works pretty good.

Pay attention to all of the weakest links as well (doors and so on)

/Gustav

Last edited by gustav82; 24th April 2015 at 08:58 AM..
Old 24th April 2015 | Show parent
  #13
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Hi guys, and thanks for all the detailed explanations, specially Rod.
Sharing your knowledge with the rest of us mortals is priceless!

I really appreciate your feedback. I guess I rushed over myself and missed several important points down the road. I must re read your book even more times, haha. I going back to square one!

QUESTIONS..

Do you think I should continue pursuing the masonry / brick-wall design for isolation, or completely ditch it, go back to the drawing board and take the drywall / gypsum approach?
Can I achieve almost 80 dB of soundproofing, either way or am I asking too much for a home rehearsing room, mechanically coupled to the house?

----

Quote:
Originally Posted by Rod Gervais View Post
You cannot float a masonry wall on that material - eventually the wall will fully compress the insulation and at that point nothing is structurally decoupled/isolated......
Quote:
Originally Posted by Rod Gervais View Post
If you are bound and determined to do this (personally I would not bother trying to float those walls) then the isolation system needs to be properly designed not only from the perspective of selecting a proper product as the base material - but also the total loads that are going to bear on it..... you will have greater loads on the bearing walls than the non bearing walls.
I totally overlooked this aspect. Thanks.

For the first moment, I erroneously thought it should be relatively simple, as I depicted on the first attached images. Here in Argentina, building masonery/brickwalls is not that expensive as I believe it is in the US, and it's the traditional approach for nearly every residential building.

Even more, I may have been self deluded..
In the book Recording Studio Design book, by Phillip Newell p. 36 (Focal Press, Second Edition) there's a design of a hollow sand-filled concrete block wall, laid on a plywood base, over a 10cm 140Kg/m3 mineral wool base. I guess there's something I'm not getting here. Just the wall, no ceiling. (Would it be ok if I posted that image here? Copyright?)



Quote:
Originally Posted by Rod Gervais View Post
Now - I would also be concerned about how all of this is being braced laterally......... the bottom of wall needs to be locked into place as does the top of wall (and possibly the center of the wall depending on wall height.) This can be done either through the use of properly sized lateral sway braces, or by developing a wall reinforcement design using grouted cores with rebar.....
The top of the masonry wall should utilize a reinforced bond beam.
This was my main concern on my original post: Stability. Thanks for clearing things up!



Quote:
Originally Posted by Rod Gervais View Post
You should also pay close attention to the means by which the ceiling frame is attached to the face of that masonry wall....... based on your design concept you are going to have to focus on/deal with shear conditions with the fasteners you use at the continuous plate you need to carry those joist (unless your plan is to let them into the masonry - however that is not an approach I would recommend.) If you are not letting them in then your detail is missing the very important continuous member that these joist are going to be attached to in the inside face of that masonry wall.

Assuming a plate attached to the wall you need a fastening system designed for attaching that member to the masonry - and then joist hangers to attach the ceiling joist to that plate.
Rod
My idea was to install the beams using brackets screwed to the brickwall. I believe that at the same time I would be adding rigidity to the inner structure.
The gypsum boards were going to screwed to the wooden beams, caulked and sealed in the ceiling / wall intersection. (I am assuming that although the ceiling is mechanically coupled to the walls, the walls were supposed to be "floated". Any issues with that?



Quote:
Originally Posted by Rod Gervais View Post
Regardless of which system you use you also need to provide mid span bracing for those ceiling joist to avoid issues (in the long term) with the center of the joist rotating under load.
I assumed that would be necessary, but not completely shure. Thanks!



Quote:
Originally Posted by Rod Gervais View Post
Once you lock that mass between layers of drywall it's only value is the mass......... and the cost is huge compared to what you could gain by simply losing the MLV and adding another layer of drywall.
Great!



I'm positive that all this information will be great for the entire community.
Thanks a trillion!
Old 25th April 2015 | Show parent
  #14
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Quote:
Originally Posted by spacefolder View Post
QUESTIONS..

Do you think I should continue pursuing the masonry / brick-wall design for isolation, or completely ditch it, go back to the drawing board and take the drywall / gypsum approach?

Can I achieve almost 80 dB of soundproofing, either way or am I asking too much for a home rehearsing room, mechanically coupled to the house?

For the first moment, I erroneously thought it should be relatively simple, as I depicted on the first attached images. Here in Argentina, building masonery/brickwalls is not that expensive as I believe it is in the US, and it's the traditional approach for nearly every residential building.
First off - you need to (more clearly) define exactly what you intend to achieve here......

By which I mean - "almost 80dB" of isolation at what frequency?

Achieving a weighted average of 80dB is a pretty big undertaking. Achieving 80dB @ 20Hz is a much more difficult goal to reach (and would put your overall isolation at much more than a weighted 80dB average.)

Having said that - masonry is an excellent means of achieving good isolation levels - and is both readily available in your area and the more cost effective means of doing your build........

So no - I would not abandon that approach.....

However if I were you what I might consider would be moving from 4" block to 8" block.

With 8" block you gain the ability to have a self supporting inner structure.... one that will not require isolated lateral bracing. You will always get better isolation when you don't have to brace the inner structure off the outer one (there is always some loss that takes place through the braces - even when properly designed/loaded)

Add to that the increase in mass and you go a long way towards reaching your goal.

I would lose the idea of floating this assembly......

We do commercial builds (inside of existing buildings) all over the world that achieve great levels of isolation yet the walls are directly coupled to the slabs...... and those slabs run from the tenant space to other tenant spaces- or (sometimes) to adjacent studios - yet isolation isn't really an issue.

Sure - given new construction altogether I would opt to isolate the various slabs between rooms - and there is some small gain there when doing so, at very little cost in the scheme of things - but not so much in existing buildings.

Quote:
Even more, I may have been self deluded..
In the book Recording Studio Design book, by Phillip Newell p. 36 (Focal Press, Second Edition) there's a design of a hollow sand-filled concrete block wall, laid on a plywood base, over a 10cm 140Kg/m3 mineral wool base. I guess there's something I'm not getting here. Just the wall, no ceiling. (Would it be ok if I posted that image here? Copyright?)
I really don't need to see the image....... I have to believe that you accurately copied what you saw in the book....... but I just did the math - so I know what's going on.......

As I said - this is not an approach I would take....... I would concern myself with creating a stable brace for the bottom of the wall...... in my mind that equates to no only not trying to float it - but also to tying the reinforcement in the wall directly to the slab.

You indicate that your slab is a full 8" thick - if that is the case (assuming it is fully resting on a good base and there are no concerns for settlement) then it should not be an issue loading it.....

Quote:
My idea was to install the beams using brackets screwed to the brickwall. I believe that at the same time I would be adding rigidity to the inner structure.
If I were designing this I would be using a ledger board attached to the masonry - and then hanging the ceiling joist using joist hangers......

I an not real crazy about the idea of attaching hangers directly to the masonry, this ceiling is going to weigh a whole lot - besides which - the ledger will provide you with a continuous point of attachment for the ceiling below - which helps tons when it comes to isolation of the perimeter.

Quote:
The gypsum boards were going to screwed to the wooden beams, caulked and sealed in the ceiling / wall intersection. (I am assuming that although the ceiling is mechanically coupled to the walls, the walls were supposed to be "floated". Any issues with that?

The walls are independent except for the base....... the ceiling is independent except for the walls........ the walls are resting on a thick concrete slab that is resting directly on top of the earth..... I really would not concern myself as mentioned above.

Listen - when I designed Studio H at Hit Productions in Manila I did not isolate the walls from the slab...... this studio is on the top floor of the building - and yet there are no isolation issues when it comes to the spaces below through that elevated concrete deck even though the walls are directly coupled to that deck.......

IMHO you are simply over thinking this........


Best of luck,

Rod

Last edited by Rod Gervais; 25th April 2015 at 12:54 PM..
Old 25th April 2015 | Show parent
  #15
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Quote:
Originally Posted by Rod Gervais View Post
./.........

Having said that - masonry is an excellent means of achieving good isolation levels - and is both readily available in your area and the more cost effective means of doing your build........

So no - I would not abandon that approach.....

However if I were you what I might consider would be moving from 4" block to 8" block.

With 8" block you gain the ability to have a self supporting inner structure.... one that will not require isolated lateral bracing. You will always get better isolation when you don't have to brace the inner structure off the outer one (there is always some loss that takes place through the braces - even when properly designed/loaded)

Add to that the increase in mass and you go a long way towards reaching your goal.

I would lose the idea of floating this assembly......

We do commercial builds (inside of existing buildings) all over the world that achieve great levels of isolation yet the walls are directly coupled to the slabs...... and those slabs run from the tenant space to other tenant spaces- or (sometimes) to adjacent studios - yet isolation isn't really an issue.

Sure - given new construction altogether I would opt to isolate the various slabs between rooms - and there is some small gain there when doing so, at very little cost in the scheme of things - but not so much in existing buildings.
I'll second that
Quote:
Originally Posted by Rod Gervais View Post
.............

The walls are independent except for the base....... the ceiling is independent except for the walls........ the walls are resting on a thick concrete slab that is resting directly on top of the earth..... I really would not concern myself as mentioned above.
I agree...

Even for a new building, two heavy and parallel walls, close to the each other (dilatation type of "coupling") built on the same foundation (which is very heavy and already dampened & tightened, deep in the ground) have reasonably better insulation than only one wall built on the same foundation, because (more important) strong coupling between two surfaces of (same and stiff) wall, which is very problematic to decrease... even if wall is built from sand filled cinder blocks...

so, for countries where earthquakes aren't exceptionally rare, real floating (spring decoupled) room-in-the-room constructions are not always a reasonable choice... some compromises may be a better way...



Last edited by boggy; 25th April 2015 at 10:54 PM..
Old 26th April 2015 | Show parent
  #16
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Guys, thanks for your time and patience,
really learning a lot here!

Quote:
Originally Posted by Rod Gervais View Post
So no - I would not abandon that approach.....
However if I were you what I might consider would be moving from 4" block to 8" block.

With 8" block you gain the ability to have a self supporting inner structure.... one that will not require isolated lateral bracing. You will always get better isolation when you don't have to brace the inner structure off the outer one (there is always some loss that takes place through the braces - even when properly designed/loaded)

Add to that the increase in mass and you go a long way towards reaching your goal.
Excellent! I´ll go for the 8" masonry isolation wall.
Traditional "baked earth" bricks, which are actually 9" aprox, glued with cement (mortar).



Quote:
Originally Posted by Rod Gervais View Post
If I were designing this I would be using a ledger board attached to the masonry - and then hanging the ceiling joist using joist hangers......

I an not real crazy about the idea of attaching hangers directly to the masonry, this ceiling is going to weigh a whole lot - besides which - the ledger will provide you with a continuous point of attachment for the ceiling below - which helps tons when it comes to isolation of the perimeter.
Very good points here, specially I like "the ledger will provide you with a continuous point of attachment for the ceiling below".

Rod, for the "Ledger Board" you mean something like this picture, but more "heavy duty", calculated for my roof´s weight?
Attachment: Ledger Board Joist Hanger 01.jpg

BTW, something I didn't quite get in your last reply..
Should I:
1) Nail de new gypsum ceiling layers to this hanged joists from beneath?
or
2) Aim for isolated hangers and a steel frame hanging from the joists?



Quote:
Originally Posted by Rod Gervais View Post
Achieving a weighted average of 80dB is a pretty big undertaking. Achieving 80dB @ 20Hz is a much more difficult goal to reach (and would put your overall isolation at much more than a weighted 80dB average.)
I see what you are saying here. Would it be correct to assume I need 80 dbA? Rock band inside = 120 dB (reaching this high spl, should I use dbC?), "acceptable" noise inside the house without bothering = 40 dBA. dB(A) Is this correct?



Quote:
Originally Posted by gustav82 View Post
But as mentioned before, maybe you should try some other solution. Maybe with a simple extra drywall (with x number of layers and 2x4 studs for instance), decoupled from the existing wall. This "light" wall could be standing on a wood chip board (floor type, with joints that you glue), and a thin layer of very rigid insulation under that. Also you should use a vapour barrier beneath, protecting the wood from the concrete slab (which can get moisty from time to time).
A lot cheaper/easier, maybe not perfect. But I did something similar, and it works pretty good.
/Gustav
Thanks a lot Gustav, you´ve been helping a lot since my first post. I really do appreciate that.
I´ll try to go ahead with the masonry approach for now, but who knows.. I´m still trying to make sense!



Quote:
Originally Posted by boggy View Post
so, for countries where earthquakes aren't exceptionally rare, real floating (spring decoupled) room-in-the-room constructions are not always a reasonable choice... some compromises may be a better way...
Thanks Boggy for chiming in, great info!
Luckily, no earthquakes around this place



Quote:
Originally Posted by Rod Gervais View Post
IMHO you are simply over thinking this........
Just trying not to screw up the whole thing, haha heh

Last edited by spacefolder; 26th April 2015 at 06:39 AM.. Reason: Missing quotes!
Old 26th May 2015 | Show parent
  #17
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Hi guys, after thinking for a while on how to go with the ceiling, I'm back..

Quote:
Originally Posted by Rod Gervais View Post
If I were designing this I would be using a ledger board attached to the masonry - and then hanging the ceiling joist using joist hangers......

I an not real crazy about the idea of attaching hangers directly to the masonry, this ceiling is going to weigh a whole lot - besides which - the ledger will provide you with a continuous point of attachment for the ceiling below - which helps tons when it comes to isolation of the perimeter.

Rod
I've added an attachment..
"ALTAMIRA sketchup 05 cross section ceiling detail n1"

The idea to install a ledger boards with joist hangers, and the beams hanging from there. Separation between beams would be around 55 cm.

Questions:

1) Layers of plaster boards will be screwed from below, one at a time, properly caulked and sealed. Will this system withstand the weight of the ceiling? I mean, will the uppermost layer support the other three or everything will rip apart? Should I use successive longer screws on each layer so as to always "connect" the last layer to the beam itself?

2) I am assuming that the ceiling will act together with the walls, as one rigid structure (inner room). Is this ok, or should I mechanically decouple the roof from the walls be means of iso hangers, etc.?

Any thoughts are very welcome..
Thanks a trillion!
Old 26th May 2015 | Show parent
  #18
Gear Nut
 

Quote:
Originally Posted by spacefolder View Post
Hi guys, after thinking for a while on how to go with the ceiling, I'm back..



I've added an attachment..
"ALTAMIRA sketchup 05 cross section ceiling detail n1"

The idea to install a ledger boards with joist hangers, and the beams hanging from there. Separation between beams would be around 55 cm.

Questions:

1) Layers of plaster boards will be screwed from below, one at a time, properly caulked and sealed. Will this system withstand the weight of the ceiling? I mean, will the uppermost layer support the other three or everything will rip apart? Should I use successive longer screws on each layer so as to always "connect" the last layer to the beam itself?

2) I am assuming that the ceiling will act together with the walls, as one rigid structure (inner room). Is this ok, or should I mechanically decouple the roof from the walls be means of iso hangers, etc.?

Any thoughts are very welcome..
Thanks a trillion!
1) yes, you need to screw all layers of dry wall to the studs/joists. And dry wall screws are sold in different lengths for this purpose.
Old 26th May 2015 | Show parent
  #19
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Quote:
Originally Posted by gustav82 View Post
1) yes, you need to screw all layers of dry wall to the studs/joists. And dry wall screws are sold in different lengths for this purpose.

I agree with this...... they do make laminating drywall screws....... however I would never use those on a ceiling unless I was also using construction adhesive as a part of the process....... and I never use construction adhesive as a part of the process.........

Quote:
Originally Posted by spacefolder View Post
2) I am assuming that the ceiling will act together with the walls, as one rigid structure (inner room). Is this ok, or should I mechanically decouple the roof from the walls be means of iso hangers, etc.?
Assuming that when you speak of mechanically decoupling the "roof" you are actually talking about the "ceiling" then you assume correctly......... there is really no reason to isolate the ceiling from walls that are already isolated.......

You have an outer shell and an inner shell....... the 2 should not be coupled (except for however they couple to the earth) - but there is no reason to bother trying to decouple the various elements from one another within the assemblies themselves.

Rod
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