Floor structure and substructure in the attic with filling?

Hello Markus. Have you ever wondered while shopping for, for example, toothpaste, why besides Colgate other manufacturers also offer such a product? Did you then also ask what advantages and possibly disadvantages the other products have? Certainly not. If I wrote that you can also use OSB boards for the system construction, then I certainly don’t want to get involved in a discussion about evaluations. You can take whatever you like. If OSB boards work, then I write that. Whether you decide on FERMACELL, KNAUF, wood chipboard, wooden planks, or OSB, that is up to you. It’s all a question of marketing, I say. I heard from men who wear suspenders at the same time as a belt so that their pants don’t slip. You can do that! Also, laying soft fiber boards over the mineral wool of the individual compartments. That also works, is not harmful, and is permissible, even if completely nonsensical. My tip: leave that to a professional who has already successfully completed this trade. When I read the reactions, I come to the conclusion that more damage could be caused to drywall due to ignorance than cost savings can be achieved on the other side. We can give assistance in the form of tips here (in a public forum), but this is the wrong place for workshops that are supposed to serve the DIY handyman. Regards: KlaRa, this time from Augsburg

So we have now finally decided on the following option:

- Mineral wool between the beams
- 22 mm OSB
- 10 mm wood fiberboard
- 18 mm Brio board
- Finished floor covering (e.g. vinyl)

We still have the following questions:

[*]Which mineral wool should we use between the beams? A high insulation value is actually not necessary here, since both the room below and the one above will be heated?! So which exact mineral wool would you recommend for us here? (Please provide the exact designation)

[*]To reduce the creaking of the OSB boards on the beams a bit, we would like to stick or staple felt strips (e.g. 5 mm) or something similar in strips onto the beams. Which exact felt or which product would you recommend here? Please also provide the exact designation so that we can look it up calmly on the internet.

[*]With which screws should I screw the OSB boards onto the beams? Screws with a full thread or screws that do not have a thread along the entire length? Which type of screw is better here so that the OSB boards do not creak later?

[*]We are currently considering whether to use Knauf Brio in 18 mm or 23 mm on top of the 10 mm wood fiberboard? How do these two boards differ in terms of load-bearing capacity? We are aware that the 23 mm is thicker and heavier. But what would be the advantage of using the 23 mm board?

Thank you very much in advance for your information and your effort.

Regards,
Markus

Hello Markus.
Regarding question 1: It doesn’t matter! You are correct in recognizing that thermal insulation is not necessary. This is about soundproofing. And we can only manage that by adding mass. So possibly a mineral filling on a dust protection foil, if the crawl space floor can bear the weight.

Regarding question 2: You surely have a flooring wholesaler nearby?
Ask them for a thicker felt covering, not too tightly felted!!

A felt covering, for example in panel form, with high walking comfort would be good. You can cut it into strips with a triangular blade, stack 2 or 3 layers on top of each other, and then staple it onto the joists in such a way that no unintended shifting can occur later during construction or use.

Regarding question 3:
Use only and exclusively SPAX screws with continuous threads!!!!!

Regarding question 4:
If you have the build-up height: take a 22mm OSB board, that’s completely sufficient. The thinner it is, the more the system will resonate. The more mass, the better.
Humorously noted: in physics it always applies: “Mass wins!”
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Good luck: KlaRa