New floor in damp basement

[Stew]

Hello,

I have discovered that we have moisture in the basement, coming from the concrete slab. It's not a lot, but enough for me to remove the risk construction with wood against concrete that is there today, to do it right. I am planning to expose the concrete and apply the following combo:

Platon membrane
Cellplast S100, which I'll rout grooves for underfloor heating pipes with a plunge router
Underfloor heating pipes placed in the grooves
Floor gypsum
Carpet

A few questions:
* Would this work?
* Would there be any benefit in laying, for example, plastic or a mat under the Platon membrane? Or should it be directly against the concrete?
* The concrete is quite uneven today, do I need to even it out? Can I use concrete for that?
* Is it possible to ventilate under a Platon membrane, or is there too little space between concrete and the membrane?
* Is floor gypsum too weak? Isn't it easy to damage it when it lies under a carpet?

Best regards,

Stefan

 

[Jan-Å]

An uneven concrete slab is probably easiest to level with self-leveling compound, that's what I would have done. I laid a Platon mat with polystyrene with ready-made grooves, waterborne underfloor heating with spreader plates, and laminate flooring on top of that, works well so it should work with gypsum board and carpet too, but I think it's easier to spread the heat with laminate flooring than with gypsum+carpet.

The Platon mat is intended to ventilate moisture up through the baseboards, but I think I've read somewhere that the function isn't 100%-effective, but I'm no expert in that area. We didn't have any moisture at all in our slab when we measured.

 

[Stew]

An uneven concrete slab is easiest to level with self-leveling compound, that's what I would do.
I laid Platon mat with foam with pre-made grooves, water-based underfloor heating with spreading plates and laminate flooring on top, works well so it should probably work with floor gypsum and mat too, but I think it's easier to spread the heat with laminate flooring than with gypsum+mat.

The Platon mat is designed to ventilate moisture via the baseboards but I believe I've read somewhere that the function is not 100% effective, but I'm no expert in that area.
We had no moisture at all in our slab when we measured.

Thanks for the answer!
Okay, then I'm not completely off track.

Self-leveling compound is what's needed, then, and before applying it I guess I clean the concrete.

Then I need to build up the walls first (which are also gone) and the floor last, otherwise, I'll have issues with the ventilated baseboards.

Does anyone know if there is a mechanical ventilation solution for Platon mat? There's so little air between the concrete and the mat, I can't fit a fan directly.

 

[nimhed]

Gypsum floorboards with paper coating can also mold. But it might work if you have foam insulation with underfloor heating underneath.

 

[Stew]

Floor gypsum with paper covering can mold as well. But it might work if you have Styrofoam with underfloor heating.

Yes, I have thought about that too. Came to the conclusion that gypsum should handle it better than chipboard? Or is chipboard preferable?

 

[Jan-Å]

Well, I've read somewhere that the "platonmattan" doesn't ventilate that well on its own, but since our slab was dry, we were satisfied with that system.
There are others with more active ventilation like the Nivell system, I don't have personal experience with this, but there are old threads about it and alternative systems on the forum.

Before applying the floor levelling compound, there's a primer that you brush/roll on to increase adhesion.

In a basement, gypsum is probably better than chipboard; as I mentioned, I laid laminate flooring directly on the polystyrene, but otherwise, tiles directly on the concrete/floor levelling compound are probably the best if there are moisture migrations in the slab.
Personally, I prefer underfloor heating, even if there's a risk of moisture problems, also if you completely turn off the heating during the summer months.

 

[Milkshaken]

I think you should check out the nivellsystem http://www.nivellsystem.se/sv/
A bit trickier to lay than this Giha...: http://www.hisab.se/website1/sd_page/9/1/index.php?

Both floors cost a bit... (Around 5-700:- /sqm) but they are worth every penny....
In Giha, for example, you have Styrofoam under the board..... Then no additional underfloor heating is needed.....
Both floors can be equipped with a ventilation duct system that airs out moisture and odor.... It is preferably laid with ventilated skirting, (As you yourself said you would have)

 

[Milkshaken]

I'm including some pictures of the Gihagolvet I laid a while ago..... I'll take a photo when it's completely finished.....

 

[Farzan]

Personally, I prefer underfloor heating even though there is also a risk of moisture problems if you turn off the heat completely during the summer months.

I agree. In our basement, there is hydronic underfloor heating and tiles (done by previous owners) on top of an almost uninsulated slab, and there is indeed reverse moisture migration and a rather damp climate when we have the heat off during the summer months. But it's still better than if we had an ice-cold basement all winter long (we have both a shower and laundry room there).

 

[Plutus]

When I redid my basement floor, which was quite uneven, I screwed metal brackets to the floor and leveled wooden beams. I insulated between the beams and used perforated concrete plywood (almost free) on top. On top, I added a carpet intended for balconies (ventilated and non-organic). The result was a breathable floor, soft and warm to walk on. No wood against the concrete, cheap! Although without underfloor heating.

 

[Danne1]

Hi, I am also working on my basement and I have installed plattonmatta and cellplast on it. I feel like I hear a cracking sound when I walk on the cellplast now. Does anyone know if it will settle down after I put on the foam and parquet?

 

[Stew]

Is there, by the way, special cellplast used for floors to prevent them from creaking and squeaking?

 

[Stew]

An uneven concrete slab is probably easiest to level with self-leveling compound, that's what I would have done.

Follow-up question. Why self-leveling compound? Is it for adhesion or what? It becomes much more expensive than leveling with concrete (4-5 times as expensive).
Can't concrete be used instead?

 

[fulingbusen]

Follow-up question. Why self-leveling compound? Is it for adhesion or what? It's much more expensive than leveling with concrete (4-5 times as costly).
Can't you use concrete instead?

Concrete might crack if you cast a thin layer?

 

[Stew]

Concrete might crack if you pour a thin layer?

Sounds reasonable! Can someone confirm if that is the reason?