Laying new chipboard flooring, joists not straight. + Insulation question

[eddiw]

Hello!

Thanks
We are in the process of renovating our bedroom, which is on the upper floor of our 1.5-story house. We have removed the old wooden floor that dates back to the 1940s and also removed all the slag stone and wood shavings that were in the joists. This is to replace with new insulation.

Question 1: Well, when I place the level between the joists (between two or more joists), there's a slight height difference in the joists. Under the old wooden floor, there were strips fastened with nails (with tar paper nails) of some form of wood fiberboard to ensure the joists are at the same height. The plan now is to lay flooring panels, and the flooring panels should be glued to the joists.
Is it okay to add some material to the joists to "level" them and then glue them first, to later glue the flooring panels on top?
What kind of material should I add to the joists to "level" them, so to speak? I'm not going to put new joists on the old ones; that's too much work, and the old joists are a bit warped, which makes it difficult for the new ones to align properly. I think it's easiest to put something between the joists and the flooring panels.

Additional question: Why do you have to glue the flooring panels to the joists? I understand it needs to be done at the seams, but it will be a nightmare the day you need to remove the flooring panels again. How do you do that? With just screws, you can simply unscrew them; with glue, there will be residues left forever.

Question 2:
Regarding insulation, is this adequate for sound insulation in the joists?
https://www.byggmax.se/isolering/mineralull/stenullsskiva-paroc-solid-p16890
I have a subfloor where I plan to place the insulation (so I don't have to lay the insulation directly on the ceiling of the lower floor). Is it okay to do so?
What thickness is needed? 45 mm or 95 mm?

Grateful for all thoughts and answers!

 

[Demmpa]

2) that insulation is soft so if they are placed on joists at the outer edges, there is a high risk that the insulation will slide off the joists.

 

[eddiw]

2) That insulation is soft, so if placed on the edges of the joists, there's a high risk that the insulation will slide off the joists.

There are boards in the blind floor, so the insulation lies on them in that case. But what could be better insulation?

 

[vectrex]

The best and easiest way is to buy straight 45x95 studs and screw-glue these to the side of your old studs. This way, you can level these so they are all even and at exactly the same height! On this, you then screw-glue your floor particle boards! It becomes solid and good!

Using shims to get the right height is not as effective because you lose the synergy effect between the studs and the floor particle boards.

 

[justusandersson]

The reason for gluing the chipboard to the joists is that only then do you achieve full interaction between the joists and the chipboard. The chipboard acts as an extension of the joists, which in turn become stiffer. Whether this is necessary in your case depends on the cross-sectional dimensions of the joists and their span. If you find out this information, you will get an answer to whether you need to glue. I understand your feeling; gluing is so definitive. It is difficult to manage with spacers. You would need to precision cut them with a band saw, which is a real challenge.

 

[eddiw]

The reason for gluing the particle board to the joists is that only then do you achieve full integration between the joists and the particle board. The particle board acts as an extension of the joists, making them stiffer. Whether this is necessary in your case depends on the cross-sectional dimensions of the joists and their span. If you find out this information, you will get an answer to the question of whether you need to glue. I understand your hesitation, gluing is so definitive. It's difficult to manage with shims. You would need to precision-saw them with a band saw, a real challenge.

Thank you for the reply Vectrex and justusandersson!

It's actually a joist next to an interior wall that's a bit higher than the others and then there's a joist in the middle that's a bit lower than the others, if I remember correctly now. It would be good if none were too high, as that means all must be adjusted.
Now let's see here, the span of the joists is 4.4 meters at the longest point. There is a chimney in the room where the joists naturally become a bit shorter.
The joists are 75x235 and one joist is 100x235. The house was built in the 1940s, so a bit crooked and slanted is to be expected..
There is also a connection to a balcony outside, where double joists have been used to support the load, making these joists a bit shorter. The center-to-center dimensions vary a bit, but are between 53 and 64 cm. So it varies.
The joists have warped and shifted a bit over the years so they are not so straight on top, so to speak.

Regarding whether to screw-glue joists to existing ones, would one place a joist on each side of an existing joist or just on one side?
A picture would indeed illustrate better how it looks. The blind floor is resting between the joists, with air space below the planks down to the ceiling.

 

[justusandersson]

It is a borderline case. The deflection is primarily decisive, and in that regard, the dimensions and span of the beams play the largest role. The cross bracing in the middle is an advantage because it helps distribute a point load to adjacent beams. There is no doubt that a glued chipboard provides a sturdier floor, but the result should be acceptable even without gluing. The solution with the subfloor and hefty beams (approximately 3x9 1/2 inches) unfortunately does not occur today.

 

[eddiw]

It's a borderline case. It's primarily the deflection that is crucial. The dimensions and spans of the beams play the biggest role. Cross bracing in the middle is an advantage because it helps distribute a point load to nearby beams. There's no doubt that a glued particle board gives a more rigid floor, but the result should be acceptable even without gluing. The solution with a subfloor and thick beams (about 3x9 1/2 inches) unfortunately doesn't occur today.

I don't experience any deflection on the beams today, unless you stand and stomp hard on them. I haven't experienced deflection when there was a nailed floor earlier either. But maybe it's best to apply a strip of wood glue on the beams anyway. Hopefully, it won't be me who needs to tear it up next time But regarding gluing the new beams, does it need to be done on either side of each beam?

How thick insulation do I need in the floor structure? When you write that it unfortunately doesn't occur today, is it then an advantage here to have it as I have it? Or is it bad? =)

The funny thing is that the ceiling is not screwed to the beams, but it's attached to another set of beams that have significantly smaller dimensions, which in some way are attached to the thicker beams. Despite this, we have a ceiling height of 2.60 meters on both the ground and upper floors. In other words, the house is very tall, especially since we also have a basement with a high plinth.

 

[justusandersson]

It is of course an advantage to have such a floor joist as you have! Today's weak dimensions, max 45x220, don't offer much in many situations.

You don't have to glue the chipboard, but it's good if you do. It's enough if you attach new joists on one side. Without going on too long about sound insulation, I would go for 95 mm mineral wool with medium density. No more.

 

[eddiw]

It is certainly an advantage to have such a floor joist as you have! Today's weak dimensions, max 45x220, are not much to come with in many situations.

You don't have to glue the chipboard, but it's good if you do. It's enough if you attach new beams on one side. Without going on and on about the soundproofing, I would go for 95 mm stone wool with medium-high density. No more.

Thank you, thank you for the response! Then I can continue the renovation I started this spring before the outdoor projects kicked off. I suppose I should also keep the cross bracing and not place a beam exactly there, but place one on either side of the cross bracing?

Before I close up the joist, I also plan to run some VP pipes for things like network outlets and such. Convenient when you have it open anyway.

 

[justusandersson]

Keep the cross-bracing, it benefits the resilience.

 

[eddiw]

Keep the cross-bracing, it benefits the springiness.

Great, thanks!

Would it be useful to add noggings between the studs in more places? Maybe not cross-bracing, but straight noggings, so to speak? I had straight noggings before, which I removed as they were quite loose. They were there because there had previously been a wall, where the tongue and groove plank rested on these noggings. (kortling/kottling? What is it actually called).

 

[justusandersson]

Kortling. On the west coast, they say kottling, just like pogram. Kortlingar have the same effect as krysskolvning, they distribute a point load to surrounding beams. In your case, they are not needed but do no harm.

 

[JLov]

If there's only one that is high, I would probably let the circular saw do the work. Rip it in place. Alternatively, the electric planer if it's just a little bit.

 

[eddiw]

If it's just one that's high, I would probably let the circular saw do the job. Rip it in place. Alternatively, use a power planer if it's just a little bit.

Hmm, next to one wall one is sitting a bit too high and in the middle, one is sitting a bit lower than the others. So it varies a bit here and there. In terms of length, they all seem to be reasonably level, at least that's something If I put a level between 4 studs, there's a gap at one of the studs, for example.