Do I need floor gypsum?

[agneo]

Hello everyone!
I have a small question...
I am going to lay tiles in the hallway of my construction and have framed at 30cm centers and using water-based heating in plates under the chipboard floor!
Do I need to lay floor gypsum on top of this or can I lay tiles directly on it?
It shouldn't flex at all when it's framed so tightly, right?
Regards, Agne

 

[Plupp 23608]

Gipsa. You must have dead material under the tiles to prevent them from cracking due to movements in the chipboard.

 

[agneo]

Okay.. but does it have to be floor gypsum or is the thinner repair gypsum sufficient? Preferably, I would like to reduce the height compared to the regular floor!

 

[Farzan]

According to the industry standard for tiling, when tiling on a wooden floor structure, it should have stiffness equivalent to joists cc 30 + 22 mm chipboard + 13 mm glued floor gypsum.

Renovation gypsum would contribute significantly less to stiffness than floor gypsum, partly because it is thinner and partly because floor gypsum itself is of a harder quality than regular gypsum board.

Then again, you can surely find people who have built more slenderly and managed...

 

[kalle26]

I am going to build a bathroom on the upper floor. I have placed a "green" flooring chipboard there and wonder if I should also lay gypsum on the floor? Why use floor gypsum at all? Does it have to do with tile installation?

We will not have a shower, just a toilet and washbasin (no floor drain), vinyl flooring on the floor, and regular wallpaper on the walls.

 

[snickarboden]

Yes, the tile requires a base that does not move. I would probably have laid floor gypsum in your case anyway because the day might come when you want to lay tiles there, and it's quite nice to have most of it prepared. The additional cost is minimal.

/Kent

 

[jon_h]

I definitely think you should use at least 12 mm of self-leveling compound instead. It won't be more expensive, you get the slope in one go, and you get enough bending stiffness for future tiling if you decide to remove the mat. There is no reason to use gypsum on the floor in a bathroom. And it becomes quite an additional cost considering how expensive the adhesive is and that you still need to level the slope on top of the gypsum afterwards.

 

[nihtila]

I absolutely think you should self-level at least 12 mm instead.

Hi! Exactly my thoughts too, and it surely matches what you write for the sake of tiles, etc.

BUT

If you consider better sound insulation against the floor below when you sing in the shower, wouldn't gypsum be preferable as well?

Generally, when it is written about sound insulation in walls, two layers are preferred instead of one; the same should apply to floors against the floor below - one layer should be better than none? However, one might wonder if there is a noticeable difference??

 

[kalle26]

Yes, soundproofing is important. Perhaps justified for this reason alone.

But if I plaster the floor, glue, and do everything according to the rules of the art... is the floor then ready for carpet laying? maybe even for tile laying? Or should one lay a masonite board or something similar on top of it all?

 

[nihtila]

Others more knowledgeable can answer that, but from what I've read before, you should use leveling compound regardless of whether there's gypsum or not, which is why gypsum is apparently "wasted" from that point of view.

However, it has never been mentioned in connection with soundproofing - if it is justified for that particular reason.

 

[snickarboden]

Hmm, one thing just occurred to me, earlier the recommendation was floor gypsum or leveling compound, but today it's only cement-bound boards that are approved in wet areas, right? The regulations changed on 1/7 this year.

/Kent

 

[jon_h]

The floor gypsum may be used for one more year, until 1/7 2008. But self-leveling compound on floor chipboard is an excellent construction, and regardless of whether you choose to lay a fiber cement board, you need to self-level on top of it, waterproofing for ceramics must not be applied directly on board material. And you also need to have a slope.

Rapid: But absolutely do not lay any masonite, self-level on the substrate to achieve the slope.

 

[MrElliott]

I absolutely think that you should use at least 12 mm self-leveling compound instead. It doesn't cost more, you can achieve the slope at once, and you get enough bending stiffness for future tile setting if you decide to remove the mat. There is no reason to gypsum the floor in a bathroom. And it becomes quite a noticeable additional cost considering how expensive the adhesive is and that you still need to level over the gypsum afterward.

If you don't have gypsum under the self-leveling compound, it will crack instead. It MUST be gypsum in conjunction with tiles or cast surfaces that are in contact with wood. Otherwise, it will crack in the long run. The gypsum acts as a "floating" surface that "absorbs" the wood's movements.

There is a reason for industry standards.

/MrE

*edit* spelling error

 

[jon_h]

MrElliott, you actually don't know what you're talking about in this case. Read the industry regulations before referring to them, and perhaps especially amendment 10/2005. Self-leveling compound on wood or chipboard is an excellent construction that is accepted by all suppliers and the building ceramics council. It is completely risk-free.

If you want to learn the basics of wet room construction, I can also recommend that you read through this thread.

Furthermore, gypsum is prohibited in wet rooms according to the new industry regulations, but the ban does not take effect until 1/7 2008.

 

[MrElliott]

Ok. Careless of me to assume from my unheated log house where the self-leveling compound cracked without gips.

Regarding gips, there are variations that are approved, right? Or am I remembering incorrectly?

/MrE