Performance/Cost data on Mass Timber Floor Assemblies for Sound Mitigation (STC & IIC)

Hello Community,

We are working on gathering data on floor assemblies used in mass timber projects and would be appreciative of any information you are able to provide for the projects you have worked on. It seems that the solutions used are all over the map, so it can be hard to nail down what the most common solutions are, and how we will stack up against them with our proposed dry floor topper panel. It would be great to know what has been found to work best, above and beyond what has been tested through the Woodworks chart of tested assemblies.

Please reach out directly if you prefer to supply information that way, or would be able to have a quick meeting in this regard.

Thank you in advance for your interest.

Monty Chong-Walden

Hi Monty,

Have you reviewed the data on Pliteq Eco-One? You need to create an account, but their database is quite extensive and user-friendly. You can also sort by “Descending embodied carbon”.


Thanks very much Forest. I’ve communicated with Aedan at Pliteq, but he never mentioned this resource. I’ll check it out, as they seem to be one of the big leaders in this space!
Much appreciated.

I am a structural engineer, so I am not the one specifying it, but I typically see 1 to 2 inches of Gyp-Crete or equivalent (depending on acoustic requirements). We have also used 3+ inches of concrete for reinforced diaphragms (for seismic loads), but we’d prefer to go as light as possible to save weight on the supporting timber.
You have a fascinating product. Good luck!

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Hey Adam,
Thank you for your reply and support. It looks like you and Holmes are doing some great work on mass timber buildings around the world.
I would imagine that there would be some type of sound mat or decoupler under the gypcrete or concrete?
Also, it would be great to understand “lightweight as possible” as I understand there is some benefit of weight in stopping wave transmission through the CLT.
If there is anyone you work with that can answer more questions on this, an intro would be greatly appreciated!

Yes. Mass is needed to meet acoustic requirements, and there is almost always an acoustic mat at the top of the timber floor panel. But added weight requires the timber to be thicker, and seismic and foundation systems to be bigger, which drives up cost. It’s a balance. It needs to meet all the requirements. There is also a 1” thick non combustible topping requirement for Type IV Mass Timber in the IBC.
I will DM you some acousticians I know.

Thanks for the further explanation Adam. It would be good to know what the “added weight” requirement looks like and how much weight actually starts to make a difference, as we are able to adjust the density of our panels, as needed. This may also apply to the fire-resistance, but these are bigger explorations.
I received your DM and will contact the acousticians to get more info. Much appreciated!


I was wondering to ask you what is the best substitute for Gypcrete and Acoustic Mat in Tally database?


I asked others about this, and it seems the best way to add these materials are to add them to the Tally impacts post-process. EC3 ( has EPDs for gypcrete and acoustic mat, and although these only include cradle to gate impacts, they are better than nothing.
Perhaps there is something similar in Tally, say concrete in replacement of gypcrete, and you could scale the thickness by the difference in impacts, but I haven’t done that personally.

Thanks for the information.

I have found also the nylon carpet as the closest option to acoustic mat in Tally. However, I am not sure if its the best choice.