Author Topic: Remediating old timber frame ceiling and floor - Containing pumice (rocks)  (Read 2690 times)


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I am after advice about insulating timber frame ceiling and floor in an old flat.

My flat is one of six in a sandstone waterfront building, circa 1905. There are six floors. Each flat takes up one whole floor. All the walls are between 350mm and 550mm(!) thick solid sandstone.

The floor/ceiling assemblies are timber frame. Each floor/ceiling consists of one set of 8"x2" timber joists at 18" centres.

The floors are old tounge & groove timber, nailed to the top of the joists, with masonite and carpet on top.

The ceilings are 2 layers of 16mm plasterboard (32mm total), screwed or nailed to the bottom of the joists. (I imagine this replaced a lathe-and-plaster ceiling at some stage)

The only "insulation" is a vintage layer of PUMICE (lightweight rocks) in the floors. The pumice is supported by a layer of timber planks halfway (4") up the joists. These planks are supported by 1"x1" timber battens nailed to the sides of the joists.

My apartment is a middle floor. I get major noise from both upstairs and downstairs. In particular sound system bass (upstairs and downstairs). Also a booming noise when people walk upstairs. I have read that walking is about 40Hz, which may coincide with a resonance frequency of some rooms.

As a proof on concept, I want to remediate the ceiling and floor in my living room. This room is 7000(mm)L * 4000W * 3700H. It is like 2 squarish (cube) rooms joined together.

I can remove my ceiling and my floor. I can also work on the common property timber frames, subject to structural considerations. I could remove the pumice from the floor, but removing the pumice from the ceiling would be difficult from below. If I remove the pumice, then I could remove the intermediate layer of timber planks.

I would be getting someone in to do the work. Cost of materials is not a major issue. But labour is very expensive in my area (Sydney Australia). I could afford to spend 100K AUD insulating just the living room, but would hope to pay less than half that.

I understand the three most important factors are: Mass, air-tight seal, and decoupling. I have also read that 2 leaf is better than 3+ leaf.

But I am confused about the layer of pumice. On the one hand, it is mass, which is good. On the other hand, the pumice is supported by a thin layer of timber planks that may constitute a third leaf, which is bad.

Any suggestions as to the best approach, pretty much regardless of cost (short of buying the flats upstairs and downstairs) would be welcome. I understand the basic concept of ideally having just 2 leaf, with lots of mass in each leaf. Also, I could put in a new separate set of joists for ceiling.


Randy S

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Re: Remediating old timber frame ceiling and floor - Containing pumice (rocks)
« Reply #1 on: February 02, 2015, 05:01:26 PM »
From your post I see that you do have an understanding of the principles.
The question is how to implement them which shouldn't be to hard if you have access to the materials.
Just remember that if you remove mass you have to put it back in some form or another after you have decoupled the system.
After that has been done you must increase the mass value to give improvements of the systems.
2 layers are better then 3 layers, you are on the right track
decouple the direct connections as much as possible
increase the mass by at least 2 x
insulate the hollow spaces with insulation
and finally seal seal seal the whole system air tight from top to bottom.

Randy S.


  • Guest
Re: Remediating old timber frame ceiling and floor - Containing pumice (rocks)
« Reply #2 on: February 03, 2015, 06:14:56 AM »
Thanks for your reply. Your advice to end up with at least twice the mass (regardless of other improvements) makes sense.