Puck numbers and placement

JohnGardner · Post by **JohnGardner** » Mon May 23, 2005 7:43 am

Well after alot more reading and info gathering I have found my room weight was slightly wrong due to a dodgy kg to pounds conversion.

I have attached my new weight table and as you can see my room will be 4700pounds including two people and the gear.

This room will be constructed with the inside out system with two layers of 13mm plasterboard, floated floor on 90x45mm etc.

If I work on sharwards tests one 90x45x25mm (3 1/2x 1 1/2 x 1) puck (Neoprene-60duro) will take about 300pounds of pressure to acheive 10/15% compression. This basically means I need approx 15pucks.

My floor aera is 11.04m2(118sqfeet).

So I need One puck every .736m2 (7.9sqfeet).

This is fine, and sounds OK in principle however the original wooden floor joists that I am building overtop off run at 600mm centers (23inchs) from the existing wall and I have been told many times that my new pucks must rest where the existing joists run in the existing floor.

Because I am starting my new floor and walls about 100mm out from this existing wall I cannot put them at .736m intervals and have them placed on the original timber joists. The first one nearest the wall will not be on top of the origianl joist and so on (domino effect!!)

So what's worse, or best!!

(a)pucks that do not rest on the original joists but are correctly placed at .736m2 intervals to generate the correct spring for the expected room weight.

(b)about 25% more pucks than I need, therefore not creating the correct spring, but they will lie on top of the existing joists at 600m with extra not on top of joists around the edge of the room.

(c) What about if I reduct the puck size (not thickness). Will that have any effect on the amount I need?

Help appreciated everyone:

JG

the dreamer · Post by **the dreamer** » Mon May 23, 2005 5:05 pm

Hi John,

I have been told many times that my new pucks must rest where the existing joists run in the existing floor.

Because I am starting my new floor and walls about 100mm out from this existing wall I cannot put them at .736m intervals and have them placed on the original timber joists. The first one nearest the wall will not be on top of the origianl joist and so on (domino effect!!)

Can you afford to loose some height? If so you could put the pucks on joists that you screw and glue to the subfloor (perpendicular to the original joists). This will spread out the force of the load and reduce the effect one puck has on the subfloor. But this would have to be firmly constructed to be structural "strong".
This would also give you more airspace and could reduce TL and the resonance frequency. (I don't know how the MSM is influenced by sleepers on both sides of the spring (Pucks). I'm also in the process of learning this stuff. Maybe Eric could explain?

To (a) and (b):
As I understand it (a) is the way to go if you want the decoupling work correctly. (If your calcs are ok). What I described above may be a workaround?
(b) will raise the resonance frequency which may be bad if it's in the audible range.

(c) What about if I reduct the puck size (not thickness). Will that have any effect on the amount I need?

Yes, if you reduce the pucksize you will need more pucks. If you stay with the same amount the resonance frequency is lower, but you might end up overloading the pucks. Result: Bottom out...no decoupling. Also if the work they might do it for some months an then...f.ck!

Florian

JohnGardner · Post by **JohnGardner** » Mon May 23, 2005 6:18 pm

Hi Florian,

Unfortunatlly one thing I can't do is lose anymore height. I am low, low now anyway.

I am not sure what you mean by:

"If so you could put the pucks on joists that you screw and glue to the subfloor (perpendicular to the original joists)"

I think I am doing that anyway.

The original joists run vertical on my floor plan, (top to bottom in green at 600mm). My new joists will run horizontal (right to left in red) . I was going to space these out approx 730mm apart and glue on puck at each end and then over top of each joist but as you see this would give me 39 pucks (in blue), when according to my calculations I should only be using 15.

Maybe I am getting too anal about this - but I am trying to do things right.

The the calculations verse real world just don't seem to work.

As you can see from the photo I would almost need 15 pucks just going around the edge of the floor - which is a must to take the weight of the new walls.

I am also using 45mm lumber for this floor which will needs support about every 600mm to stop sag so again I am using more pucks that the calculation shows I can use.

Very confused.

JG

the dreamer · Post by **the dreamer** » Mon May 23, 2005 8:24 pm

I am not sure what you mean by:

"If so you could put the pucks on joists that you screw and glue to the subfloor (perpendicular to the original joists)"

In the attached drawing you see what I'm thinking about.
But as I said it's just an idea to diminish the structural consequence of the pointloads. If it was an option for you, ask how it influences the acoustic behaviour.

Florian

Johnrg · Post by **Johnrg** » Tue May 24, 2005 9:07 am

Thanks Florian,
I see what you mean now.
Unfortunatlly I can't afford to do this due to height problems and budget limitations.
Any other ideas or dirction pointers anyone?
There must be a simple solution I am overlooking!!
Thanks
JohnG

Post by **sharward** » Tue May 24, 2005 2:13 pm

the dreamer wrote:In the attached drawing you see what I'm thinking about. . .

Very nice drawing! I love the 3D perspective.

JohnGardner · Post by **JohnGardner** » Wed May 25, 2005 6:58 am

OK guys,

Here's an updated floor design showing the exact placement of the original floor joists in red. These start under the existing walls and are at 600mm across the room top to bottom.

I was going to run by new 45x90mm (90mm down to save height) joists left to right at also 600mm spacing - showen in blue.

My new room weighs 4700pounds.

I have been working on a 90x45x25mm 60duro Neopreane puck.

As you can see the way by new room is designed it is almost impossible to line up any of the edge pucks (where the new walls will be built) on any of the existing floor joists except at each end of the room

(1) Is it OK to have these "wall/edge pucks" not sitting on the original joists (I kinda have no choice by the looks of it!!))

(2) If I worked on one puck at every intersection plus pucks around the edges I would need 50pucks - Based on sharwards machine shop tests on 25mm 60duro rubber (300pounds per puck) this is supper overkill.

Do I:

(1)decrease the puck thickness? if so, to what?
(2)widen the spacing gap?
(3)what about around the edges of the room that will take the weight of the walls and ceiling but have no original floor joist under them?

I was hoping to get this floor done this weekend

Thanks

JohnG

Post by **sharward** » Wed May 25, 2005 1:26 pm

JohnGardner wrote:I was hoping to get this floor done this weekend

I was hoping to start construction before last Winter, and I haven't even put two pieces of lumber together yet.

I developed a "keep my sanity" strategy by not setting any time tables -- I'm letting the project set its own schedule now.

When it comes to floating a floor, you can't be too careful, and you can't take too much time to make sure everything will be OK. If you rush things, you'll make mistakes that probably cannot be corrected. There are a number of experts who have yet to really weigh in on this. This is not to suggest that the information you have so far is bad -- but it would be good to have some second and third opinions just to be safe. Or, to be totally confused, which is quite possible!

JohnGardner · Post by **JohnGardner** » Wed May 25, 2005 6:43 pm

Hey Sharward,

Know what you mean - but I have been dicking around to long. It's action time!!

Just wanted to check it was 25mm Neopreane you tested. I have ordered some 15mm (6/8") today - as thick as it gets here in New Zealand.

I am hoping this will be a good compromise between thickness and placement on the original joists.

I hoping an expert will chip in and tell me exactlly where to put the pucks on my floor plan seeing I have the room weight, rubber type, rubber thickness and original joist placement.

Wish I new but I don't!!

JG

JohnGardner · Post by **JohnGardner** » Fri May 27, 2005 6:16 am

Can anyone help here?

Post by **sharward** » Fri May 27, 2005 9:54 am

JohnGardner wrote:. . . Just wanted to check it was 25mm Neopreane you tested . . .

Mine is ½" thick (that's 12.7mm*) EPDM -- not Neoprene --durometer 60. The puck was cut to a rectangle 1½" x 3½". See the results of the tests.

*This is according to several "inches to millimeters" conversion calculators I found on the 'Net, including this one and this one. I'm not sure where you're getting your 15mm = 6/8" conversion figure. Am I missing something?

Post by **sharward** » Fri May 27, 2005 9:57 am

JohnGardner wrote:Can anyone help here?

Bear in mind that bumping your post can actually increase the delay in getting the answers you seek. See the "Please be patient - questions are answered in the order received" portion of Steve's "Please, PLEASE, THINK about reading this before you post" announcement.

JohnGardner · Post by **JohnGardner** » Fri May 27, 2005 11:03 am

Thanks Sharward,
Probally a bad conversion on my part.It is 15mm which by my calculations isactually .5906 of an inch
Understand about bumping - sorry to be impatient!
JG