Joists, Acoustic Mat and then OSB?

[mvs]

Hello, we have a team working on our summer house. We had to replace the floor framing, so new glued laminated beams are now in place. To soundproof and also provide some thermal insulation under the parquet floor on the upper floor, we thought of building layer by layer as follows:

Parquet
5mm Acoustic Mat
Double OSB
Strips of 5mm Acoustic Mat on the floor beams
Floor beams
Mineral wool between the floor beams
1.25cm Plasterboard

Does that sound reasonable?

Here is the type of acoustic mat we were thinking of using: https://www.amazon.se/5-200-m²-ljudisolering-XPSgrönt-underlag/dp/B0C5RPMJP9

 

[MathiasS]

The green carpet is for impact sound reduction, right? It probably won't be useful if you put strips on the beams, you can likely skip that part with a clear conscience.

I would also skip OSB and instead lay double layers of floor gypsum. Much more effective for sound dampening.

 

[mvs]

The green carpet is for impact sound attenuation, isn't it? It probably won't be useful if you place strips on the beams; you can probably skip that part with a clear conscience.

I would also skip OSB and instead lay double layers of floor gypsum. Much more effective for soundproofing.

Thanks for the response! I thought that a strip of acoustic/fiber mat between the beam and OSB prevents sound from being transmitted from the OSB into the joist framework (a kind of buffer).

Isn't it risky to use only gypsum as a floor? It feels like OSB would be a more stable floor that sways less. We are also putting up new partition walls on the upper floor, so I imagine it would be easier for them to attach the walls to OSB.

 

[MathiasS]

Ok, then you have to start from square one. I assumed that the parquet was self-supporting at the joist distance you have, but I understand it's not.

The norm is that you lay a chipboard floor to create a subfloor that supports, OSB has no role in the construction to provide support. Then you lay step soundproofing on it.

 

[mvs]

Ok, then you'll have to start from scratch. I assumed the parquet was self-supporting at the joist spacing you have, but I see it's not.

Normally, you lay a chipboard subfloor to create a supporting underfloor; OSB has no role in providing structural support. Then you add step sound insulation on top of that.

They have already obtained all the OSB and plan to lay it double. Another company we hired did the same for us a few years ago in another house, and it turned out really well. What do you think about placing a 125mm gypsum board on top of the OSB and then the green fiberboard on top of the gypsum?

 

[MathiasS]

What is the distance between the beams?

 

[mvs]

What is the distance between the beams?

65cm cc. The beams are 16cm high and 10cm wide.

The house is 400 years old (stone house) so it's an approximate distance. You can follow the project here: https://www.byggahus.se/forum/threa...renoveringsprojekt.509243/page-6#post-6401651

 

[MathiasS]

...and then you lay double 11mm OSB?

That sounds highly questionable.

 

[mvs]

Each OSB is 25mm, so 50mm thick in total.

 

[mvs]

Just spoke with the construction company. They have laid 22mm OSB x 2. They may possibly add an additional 8mm OSB or 8mm drywall on top if they feel it's needed. They'll check how stable it feels tomorrow.

 

[MathiasS]

Is this in Sweden? It doesn't sound like a typical construction in Sweden. Why not stick to a glued chipboard floor (floor chipboards) which is the standard as a subfloor and will have the right load-bearing capacity at cc60 (except where you are going to lay tiles, you need to do more there). There is an advantage to using standard constructions.

.....I mean, where does one even buy 25mm OSB, it's not available in any building store here.

 

[Jansson69]

Is this in Sweden? Doesn't sound like a standard construction in Sweden. Why not stick to a glued and screwed chipboard floor (floor chipboards) which is standard as a subfloor and will have the right load-bearing capacity on cc60 (except where you're going to install tiles/ceramics where you need to do more). There is an advantage to using standard constructions.

...I mean, where do you even buy 25mm OSB, it's not available in any hardware store here.

I completely agree, I've only seen consumers lay OSB on floors in Sweden, we use floor chipboards, but I guess TS is abroad, seems common in the USA...

 

[HogeN]

Estonia sells OSB 25mm 625x2500 ^^

 

[mvs]

Yes, this is in Croatia. Completely different dimensions and materials there. It is the structural engineer who requested OSB 22mm x 2, so one must hope that it's correct.

What they are a bit behind on in Croatia is ventilation, soundproofing, and insulation, so I'm careful to double-check and explain how it's done in other countries. They have no issues with it and actually seem to appreciate it. There have been some 'aha' moments from their side 🙂