decoupling vs pumping cellulose into ceiling

[The_Mentiad]

And I'm right to understand an underlay under a parket doesn't absorb enough on its own?

(many thanks also - sorry about asking a million questions here!)

[Randy S]

absolutely not, at least for our standards of reduction...for us if I can not forecast a 50% human perceived reduction then it is up to the home owner to decide if the value of reduction is worth the cost.
now remember that 50% reduction is only a 7db-9db drop....

that is the purpose of our forum..ask as much as you would like.

Randy S.

[The_Mentiad]

Thanks,
I appreciate it - really it is saving me no end of aggravation if I know there is little to be gained by engaging the nightmare neighbour.

Looks like the ceiling has to go!

[Randy S]

a tad bit of added advice..since your neighbors are not to nice, Try to avoid telling your neighbor that you are soundproofing the ceiling. If you do, they will most likely think that is an open invitation to create more noise/impact thus making your end results change.

Randy S.

[The_Mentiad]

That sounds like advice born of experience right there!
Good thinking, many thanks.

[The_Mentiad]

So things are moving forward and it looks like the seller of the property is going to contribute financially to some work to try and fix the footfall noise.

You mentioned deflection issues. I think it is likely - much of the noise is low frequency and read that can be a sign of deflection issues....true do you think???

So I am basically thinking of deflection as structural "give" in the joists and the floor itself - am i on the right page there?

The floor upstairs squeaks a lot too - I am wondering if it is not particularly we secured.

So fixes: Cross bracing if there is deflection (flex/give) in the joists.
Should the upstairs floor be more secure? less bouncy?

Is there much else I can do to deal with deflection?

The floor upstairs is made of old hardwood beams - I was wondering whether it might be possible to shim all the points where it meets the joists from underneath will some sort of rubber shim or something of the like? to further decouple the floor and our ceiling. Does that sound doable?

[Randy S]

yes you are correct, bigger the span between load bearing walls the greater the deflection the deeper the boom.

You will need to re screw the subfloor to address floor squeaks.

Add 1/2" cement board (hardie backer) with construction adhesive and some screws to hold in place before you add cross bracing.

Decoupling the ceiling comes from the clips and channel or resilient channel.

Randy S.
 

[The_Mentiad]

So if I could get her upstairs to secure her floor better to the joists (I am not sure there is a subfloor) I might be able to bring down some of that low end boom by reducing the bounce in the floor surface itself?

[Randy S]

No, re screwing her floor will just stop the floor squeaks, the boom is from deflection...jump on the floor in the middle = boom ..jump on the floor at the edge of a wall = thump.

Randy S.

[The_Mentiad]

Yep that is what I am getting. So its cross beams I need?
Is there any point putting in more solid pieces of wood? (Those cross beams don't seem so substantial).

[The_Mentiad]

I just found an article.
Talking about "blocking" - it looks more heavy duty.
https://isostore.com/solution/fix-structural-deflection/#solution2

I'm sure this is my problem. It is exactly as you described: Boom, Boom, Boom, THUMP! - Repeat!

I wonder if the wall will still be much of a carrier of flanking noise after blocking, securing the floor, adding mass with a layer of drywall against the underside of the floor and mineral rock insulation?

If most of the sound comes from deflection, could I even have it good enough by blocking and everything above that I don't necessarily have to hang the gypsum board from resilient clips?
(If I could get away without doing that it would save me some ceiling height).

Thanks again for all this. I know it is information you would have acquired with sweat and hard work. I will make sure I take lots of pictures etc and post what I do to the forum for the good of humanity.

[Randy S]

Yes you can do blocking between joist with the same size wood as the joist themselves instead of cross bracing.

[The_Mentiad]

https://drive.google.com/file/d/0B_OvrdtrCurhelNNcDRVdy1UeGs/view?usp=sharing

So this is what we are looking at.
The boards there are her floor boards, there is no subfloor.

The low pitch booming seems to be coming from the joists/logs.

The person upstairs doesn't want to take her floor up and lay a sub floor, but she would probably let us re-nail the existing one and I am wondering this:
Could it work to say grind out all her existing nails between the joist and the floor boards with a circular grinder, and push the floor up a little and slip a rubber layer in between then re-nail her floor boards?

What do you think of that idea Randy?

[Randy S]

Well I was afraid this would be the case....
Do not pull up the floor just to slide rubber between the joist and final floor, the screws or nails will bypass the material.
Yes, you can grind or cut the exposed nails. The problem I see is the glue possibly coming up between the cracks in the flooring system.
We are going to have to seal the underside of the floor prior to doing anything else to insure this does not happen.
I would re screw the floor upstairs first.

Randy S.

[The_Mentiad]

Thanks Randy,
Yeah, I realised it was going to be impossible to pull the rubber between floor and joists. And it seems the problem is deflection - those joists are really singing a deep bass tone. They vibrate like crazy.
So:
Blocking between the joists (maybe better than cross-hatching??).
Isolated ceiling.
Screw down the floor from upstairs.

Is that going to be enough?
What I mean is really, given what you see in that picture, do you think we will get a result from doing all that without pulling up the upstairs floor and laying a subfloor?

Would it be a lot, lot, lot better with a subfloor?