Vapor barrier and moisture barrier??

[Arne999]

I have built an extension measuring 3x4 meters that is a concrete slab connected to the kitchen. The extension will have a bathroom and a laundry room with a wall in between (which is not in place yet).

Now it's time to insulate the walls and ceiling, and I am wondering how to handle the vapor barrier and waterproof layer. I will be installing a wet room membrane in the bathroom area, on both walls and floor. For the laundry room, I assume you also apply a waterproof layer on the floor at the same time as the membrane in the bathroom? To create a stop somewhere, I assume I need to install a threshold at the door to the kitchen so that the wet room membrane can be folded up.

So the question is, where do I place the vapor barrier? I can't exactly put a vapor barrier in the walls of the bathroom, as that would result in Vapor barrier -> 45mm insulation -> board -> wet room membrane... i.e., two sealing layers.

At the same time, you must connect the ceiling vapor barrier with the wet room membrane somehow so there isn't a gap. If you install the vapor barrier on the ceiling, then 45s and 45 insulation on the ceiling and walls, the plastic will disappear behind...

 

[Kicken]

The simplest way is probably to build the bathroom as a room within a room, meaning an air gap (about 20mm?) between the bathroom walls and the exterior wall with a vapor barrier.
If you only use 45mm studs, they should probably be securely attached to the exterior wall with spacers to make it steady.
It's probably just as well to skip the 45mm insulation.

Getting the vapor barrier joined with the wet room barrier is probably quite tricky, but it's okay if you manage to do it.

 

[injonil]

It is fine to have both a vapor barrier and wet room membrane if you use modern tight wet room membrane systems.

 

[Kicken]

It's fine to have both a vapor barrier and wet room foil if you use modern dense wet room foil systems.

Hmmm, should the vapor barrier be on the inside (towards the room) of the 45mm insulation then?

There's always a small risk of condensation if humid air gets between the plastic layers that cannot then dry out.
= it must be completely sealed between the vapor barrier and the wet room foil! And no moisture should be built in either.

Or is it not that critical?

 

[Dr Trä]

About 3 years ago, the rules stated that it was okay to have a vapor barrier if you set at least a 28 mm gap (45 mm in your case) so a vapor barrier should not be a problem if the rules have not changed.

 

[RoBo]

Vapor barrier sheet moisture barrier. Connect with the other vapor barrier where the walls meet the exterior wall. No organic material between the vapor barrier and the foil.

 

[Kicken]

About 3 years ago, the rules were that it was okay to have a vapor barrier if you place at least 28 mm distance (45 mm in your case), so the vapor barrier should not be a problem if the rules have not changed.

Then it should be ventilated = a couple of openings in suitable places so the air can be exchanged?

Vapor barrier board wet room foil. Join with other vapor barrier where the walls connect to the outer wall. Nothing organic between vapor barrier and foil.

That sounds okay to me.
So the vapor barrier should be on the inside of all insulation and any plywood?!

 

[Arne999]

There were several variations... I don't quite see what a vapor barrier has to do behind the waterproofing membrane. It sounds like a maximum risk for problems. If you're going to do it that way... and place the membrane right behind the drywall, then all the plumbing will "puncture" the membrane (and be sealed as much as possible..).

What about the waterproofing on the slab? I assume I need a threshold to get an upturned edge somewhere? And if I don't want a threshold between the laundry area and the toilet, I simply have to lay the waterproofing membrane over the entire floor area.

 

[Kicken]

There were several variants...don't really see what a vapor barrier has to do behind the wet room membrane. Sounds like a maximum risk for problems. If you're going to do it like that... if the membrane is placed right behind the drywall, then all the piping will "puncture" the membrane (and be sealed as best as possible..)

I would probably choose the option with an air gap between the bathroom wall and the outer wall with plastic. But I'm just a happy amateur

What applies to the waterproofing on the slab? I suppose I need a threshold to get a raised edge somewhere?? And if I don't want a threshold between the laundry area and the toilet, then I simply have to lay the wet room membrane over the entire floor area

Then you probably need to put the wet room membrane over the entire floor if you're going to do it "properly". Is there a floor drain in the laundry area? then I think it's a must to have waterproofing.

I don't know what your bathroom/laundry room looks like, but is there a risk of water often lying in the door opening between the bathroom and the laundry area? If not, then it is practically quite unnecessary to have waterproofing.

A raised edge at the threshold I often find quite silly in larger bathrooms with a shower far from the door. The threshold never gets wet, maybe you'll have a flood every 10th year, so what, it will probably dry up.

But if it's not done according to the regulations, then you'll probably get sued...

 

[Arne999]

If I apply wet room foil on the walls and let it overlap onto a stud where the foil clamps with the vapor barrier, it seems completely unnecessary to have a vapor barrier behind the foil. What function is it supposed to serve??? If moisture were to get there, it's trapped...