8mm Laminate on OSB Over Berber — Genius Hack or Disaster Waiting?

[Doist]

I rent a small 9 square meters office on a 2nd floor of a recently fresh building. The building has a central VAC system with good airflow, but it's turned off overnight. I don't expect humidity and temperature swings to be considerable anyway especially on the 2nd floor.

Now, the office's floor is covered with a very thin berber carpet, I guess it's 4mm for a hard rubber base and 3 mm of rigid pile. When walking on it feels almost like a vinyl sheet, just enough soft to isolate you from what I think is concrete (typically used in offices).

I can't have the carpet flooring as it will not pass licensing checks (the business does some health/beauty treatments), so I was choosing between SPC/LVP or laminate. It's worth saying that some "furniture" will be quite heavy, like a 85 kg treatment chair (+ client's own weight), but it's just one such item, the rest are nothing to worry about. Since I'm no expert in flooring I first listened to what all experts in the world suggest to do - remove the carpet, prepare the subfloor and install using a DPM/underlay. All because the heavy load and SPC requires an "ideal" floor. But then I realised how much effort it would take - first to remove, then when leaving the office - installing a new carpet to restore the initial look! So I did some more in-depth research about how I can keep the carpet. And it looks promising.

Current flooring
Very rigid berber (7-8 mm thick) on concrete, 9 sq meters (3 x 3 ish)

Solution
Large (2440 x 1220 x 11) OSB sheets goes on top of the carpet (3 sheets, cutting will be needed), to compensate for any instability of the carpet. Then some sound isolation and 8mm thick laminate on top. SPC/LVT was ruled out as their locking system is not enough sturdy.

Questions
1. Can I skip OSB/other kind of board completely in favour of a thicker (12mm) laminate laid directly on the carpet? Or use a thinner OSB?
2. Laminate on OSB needs some insulation. Can I go for the thinnest and rigid available?
3. OSB is class 3 so itself needs no DPM. However it still can expand and contract so the advice is to leave 2-3mm gap between the sheets. But is DPM needed for the laminate? Glued in carpet, then OSB and noise isolation - surely a DPM is too much?
4. The corridor on the right needs to be covered with OSB and laminate. I guess it's ok to have it as that area will host some static furniture unlike the left and top part of the room where most of the activity will take place.
5. The floating inset panel idea under the door - is it good? Want to use some removable double-sided carpet tape to keep it in place. Thresholds and reducers on the perimeter secured against OSB/wall/door frame (not the inset panel)
6. Any tests I should run on the carpet to make sure it's suitable for the above?

 

[crazydaze]

How were you planning on fixing the OSB down?

 

[Doist]

How were you planning on fixing the OSB down?

OSB will also be floating, with sticky tape at the butt-joined seams (T&G version starts with 18mm which is too thick for me)

 

[aveatry]

Wait a min -- so you are creating a trip hazard directly on the entrance form the door

 

[aveatry]

OSB sheets goes on top of the carpet (3 sheets, cutting will be needed), to compensate for any instability of the carpet. Then some sound isolation and 8mm thick laminate on top.
You are looking at about 30mm height then. Certainly do away with he sound insulation or maybe do away with the OSB and the sound insulation will do the 2 jobs.

 

[Doist]

OSB sheets goes on top of the carpet (3 sheets, cutting will be needed), to compensate for any instability of the carpet. Then some sound isolation and 8mm thick laminate on top.
You are looking at about 30mm height then. Certainly do away with he sound insulation or maybe do away with the OSB and the sound insulation will do the 2 jobs.

In my calculations, it was 12mm OSB + 2mm soundproofing + 8mm laminate = 22mm.
Also, there will be no obstacle to the door, because I will use (see the plan I attached) an inset panel which is pure laminate on top of the carpet, and the door already has 8mm clearance.

 

[crazydaze]

The whole thing will wobble like a jelly.

 

[Doist]

The whole thing will wobble like a jelly.

Right, of course it will. I like trampolines!
On a serious note, could you elaborate a bit more?
I’ve seen people putting laminate directly on the same floor (without OSB) in the nearby office room, and it didn’t wobble
So is it the OSB that so counterintuitively makes it *all* dance?

 

[crazydaze]

The OSB will move on the carpet, the Laminate will move on the Underlay, together they’ll move twice as much at least than if the Laminate was fitted correctly. Not only will it bounce, it will move all over the room as it’s a floating floor.

 

[Doist]

The OSB will move on the carpet, the Laminate will move on the Underlay, together they’ll move twice as much at least than if the Laminate was fitted correctly. Not only will it bounce, it will move all over the room as it’s a floating floor.

So you are saying that all floating floors, even those fitted correctly, move?

 

[crazydaze]

So you are saying that all floating floors, even those fitted correctly, move?

Yes, that’s how they are designed, they have expansion gap all round the outside, however, your proposal will cause the floor to flex up and down and expand/move across and around the space

 

[Doist]

Yes, that’s how they are designed, they have expansion gap all round the outside, however, your proposal will cause the floor to flex up and down and expand/move across and around the space

Well, the idea was to use OSB (which I think should be T&G 18mm for maximum stability) to ensure a "concrete slab like" experience for laminate. This seems to be the only decent alternative to the expensive (but surely best possible) carpet removal (and restoration when leaving the rented space) and slab levelling procedure.

The idea is to do the best possible solution based on the constraints I have. Now, if five 18 kg each boards with PVA-glued T&G will bulge and warp in my small 3 by 3 office with very good ventilation and stable conditions, then I probably have to reconsider. But will they?

 

[Doist]

OSB sheets goes on top of the carpet (3 sheets, cutting will be needed), to compensate for any instability of the carpet. Then some sound isolation and 8mm thick laminate on top.
You are looking at about 30mm height then. Certainly do away with he sound insulation or maybe do away with the OSB and the sound insulation will do the 2 jobs.

Mmm are you saying that I can skip OSB in favour of the sound insulation (which probably isn't needed if putting laminate on the carpet)?

 

[aveatry]

Mmm are you saying that I can skip OSB in favour of the sound insulation (which probably isn't needed if putting laminate on the carpet)?

I dont think it will work with the carpet underneath - I only considered it because your carpet sounds like that really nasty industrial stuff that is really thin and hard

 

[Doist]

I dont think it will work with the carpet underneath - I only considered it because your carpet sounds like that really nasty industrial stuff that is really thin and hard

This is roughly the type of carpet I will deal with. The seller says it's 6mm backing + pile.

@crazydaze does that give me a chance?