Reinforcing a floor structure for bathroom construction. Does my solution work?

[Långbro Fridhem]

If you get a 45x195 plus a 45x170 and screw-glue them, it will be enough.

Now it feels a bit safer...
Thanks so much for the help!
Then tiles shouldn't be a problem, or should one play it safe with a mat...?

 

[justusandersson]

From a load perspective, tiles are fine. Personally, however, I believe that ceramic materials requiring waterproofing on the backside should not be used on wooden structures. Tiles last for 1000 years and waterproofing lasts for 20. There is a lot of movement in wood.

 

[Åsa Lund]

The same practice as the public utility in my city operates. No tiles on wooden beams.

 

[hempularen]

But there are an incredibly large number of houses with tiles on wooden frameworks, and it works in most cases. And in the cases where the waterproofing layer starts to leak, it is often not due to movements in the wooden construction (when it is done correctly).

 

[Långbro Fridhem]

From a load perspective, tiles are fine. Personally, however, I don't think you should use ceramic materials that require a waterproofing layer on the backside on wooden constructions. Tiles last for 1000 years and the waterproofing layers for 20. There is a lot of movement in wood.

Yes, there is always a risk with tiles and tiles that grout joints will crack and, in the worst case, come loose. I'm not too worried about the waterproofing layer as I'm going to use TarkoDry which is a "plastic mat" intended as a waterproofing layer under tiles. It's even possible to replace tiles without ruining the waterproofing layer. But do you mean it only lasts for 20 years?

 

[Långbro Fridhem]

But there are an enormous number of houses with tiles on wooden joists, and it works in the vast majority of cases. And in cases where the waterproofing starts to leak, it's usually not due to movements in the wood construction (when it's done right).

That's probably true. And if you use fiber-reinforced leveling compound, the risk should be small...

 

[justusandersson]

The waterproof layer of the floors usually holds up. It is especially the transitions between floor and wall that are sensitive. For me, it's mostly a building philosophy question. One should not combine materials with such different lifespans. Before the advent of plastic mats, membrane insulation with tiles was the only way to get a waterproof floor.

 

[Långbro Fridhem]

The floor's waterproofing layer usually holds up. It's primarily the transitions between the floor and walls that are sensitive. For me, it's mostly a matter of building philosophy. One should not combine materials with such different lifespans. Before the advent of vinyl floors, membrane insulation with tiles was the only way to achieve a waterproof floor.

Yes, but what makes the difference in my case if I plan to use TarkoDry waterproofing mat? It has the same properties as a wet room mat, doesn't it? It's just intended for tiles. Then you use sealant between the floor/wall. Do you also think that tiles should be avoided even on the ground floor then?

 

[justusandersson]

Since you asked, I answered. You don't need to get too attached to it particularly. When you've been involved in construction as long as I have, you develop some pet peeves. It's the combination of tiles and waterproofing that I think has poor durability in wooden structures while also being associated with high costs. Tiles are otherwise a good material for, for example, entrances. The solution for the floor that you mention I believe is excellent. Ideally, tiles should be placed on stone material; then it lasts forever.

 

[guggen]

Have you considered cutting and casting EPS in the floor structure? It should stiffen it up, reduce movements, and increase load-bearing capacity. Or am I off track?
(Have the same thoughts with an approximately cc80 floor structure in 5*5 inches)

 

[Långbro Fridhem]

Since you asked, I answered. You don't need to attach too much to it. When you've been involved in construction for as long as I have, you develop certain pet peeves. It's the combination of tiles and waterproofing that I find has poor durability in wood constructions while being associated with high costs. Tiles are otherwise a good material for, for example, entrances. The floor solution you mention, I believe, is excellent. However, tiles and ceramics should ideally be placed on stone material, then they last forever.

I understand your thinking. I'm so focused on my specific case at the moment that I'm not thinking about constructions in general. That's why I don't see the waterproofing I'm going to use as different from vinyl flooring. But I haven't decided yet. Tiles feel more solid. Vinyl flooring is always visible so you can spot any damages in time.

Regarding the solution with the crossbeam, I spoke with an expert from the house supplier today. (Their solution is to use 30 cm center-on-center spacing when building a bathroom, which is almost impossible for various reasons. He agreed with this himself.) He thought our solution was brilliant. I say our solution because I had an idea that you and I then developed together. He even talked about including that solution in the description provided with the house delivery about how to complete the upper floor. It's such a simple and inexpensive solution that reduces the span significantly.

 

[Långbro Fridhem]

Have you thought about shortening and casting EPS in the floor structure? That should stiffen it up, reduce movements, and increase load-bearing capacity. Or am I missing something?
(I have the same considerations with a floor structure of about cc80 in 5*5 inches)

Have you thought about shortening and casting EPS in the floor structure? That should stiffen it up, reduce movements, and increase load-bearing capacity. Or am I missing something?
(I have the same considerations with a floor structure of about cc80 in 5*5 inches)

No. Now that I've reduced the span quite a bit and plan to reinforce, as well as using fiber-reinforced flow screed, it doesn't seem relevant. Then you'd need to get a good blind bottom and wrap everything thoroughly to avoid moisture in the structure, I believe.
Perhaps a solution in your case, but not in mine.
Are you also struggling to supplement with studs?

 

[guggen]

No. Now that I've lowered the span quite a bit and plan to reinforce and self-level with fiber-reinforced compound, it doesn't seem relevant. Then you probably need to get a good subfloor and carefully seal everything to avoid moisture in the structure, as far as I remember.
Maybe a solution in your case, but not in mine.
Do you also have difficulty adding joists?

Yeah.
However, I have a subfloor in the form of 1-inch tongue-and-groove boards.

 

[Långbro Fridhem]

Yep.
However, I have a blind bottom made of 1-inch tongued-and-grooved boards.

Yes, it should be stable.