A requirement is that the floor must not deflect more than 1.5mm for a point load of 1kN placed in the most unfavorable position. (In this case, in the middle of a joist). Here, one can include that the load can be distributed to adjacent joists, etc. One way is to cross brace to get more joists to collaborate for this load, alternatively to stiffen the floor with floorboards and/or ceiling panels.
Eurocode 5: Design of timber structures, SS-EN 1995-1-1 together with EKS10
Eurocode 5: Design of timber structures, SS-EN 1995-1-1 together with EKS10
Yes, you can read about that in the wood guide:
http://www.traguiden.se/konstruktion/konstruktiv-utformning/stomme/bjalklag/styvhet--bjalklag/
If you look at table 1 and the first row, we should have something to compare with:
4.2 meters
2.2 mm deflection
But they have calculated with cc60, I have half of that, which should then be able to be halved, I guess, to 1.1mm.
Or am I looking/thinking wrong?
Thanks for the help!
ps: I am super tempted to lay a crossing beam on top of the rafters and make a tie rod or two down to the floor. But don't know what other surprises that would bring. For example, the rafters collapsing, which would be quite bad.
http://www.traguiden.se/konstruktion/konstruktiv-utformning/stomme/bjalklag/styvhet--bjalklag/
If you look at table 1 and the first row, we should have something to compare with:
4.2 meters
2.2 mm deflection
But they have calculated with cc60, I have half of that, which should then be able to be halved, I guess, to 1.1mm.
Or am I looking/thinking wrong?
Thanks for the help!
ps: I am super tempted to lay a crossing beam on top of the rafters and make a tie rod or two down to the floor. But don't know what other surprises that would bring. For example, the rafters collapsing, which would be quite bad.
The point load for which you need to check the deflection is placed in the middle of a beam, meaning that it doesn't matter how closely spaced the beams are with regard to where the load is placed. However, the center-to-center distance does affect how stiff the floor structure is if you consider the interaction between, for example, chipboard and floor beams. The noggings also distribute the load more effectively with a smaller cc-distance, allowing more beams to work together.
So the answer to your question is that the deflection in the table is not halved just because you halve the cc, there are a few more factors at play.
I would probably try to avoid suspending the flooring structure from the ceiling. Connecting these could mean that your floor structure will bend due to snow load as it would then follow the ceiling's deflection.
So the answer to your question is that the deflection in the table is not halved just because you halve the cc, there are a few more factors at play.
I would probably try to avoid suspending the flooring structure from the ceiling. Connecting these could mean that your floor structure will bend due to snow load as it would then follow the ceiling's deflection.
An assessment of deflection without considering the span is not reasonable. I also do not interpret the latest version of EKS (Swedish National Board of Housing, Building and Planning's construction regulations) this way. It just becomes harder to read with each version... A maximum deflection of 1/500 of the span means 8 mm, which 45x220 c/c 300 can handle. It is better to use 22 mm K-plywood than chipboard as it is slightly lighter and significantly stiffer. Double 22 mm chipboards increase the dead weight unnecessarily.
Deflection of load (residential load) is a criterion (static) that is considered. In this case, the cc plays a role; it's a surface load, so halving the cc halves the load, which in turn halves the deflection. Then there's a sway criterion (dynamic) where you check the deflection for a designated point load in the middle of the beam. So you need to distinguish between these two.
22 K-plywood is stiffer but much more expensive than 2x22 chipboard. The slight increase in weight can even be beneficial as it becomes harder to excite the mass. However, the natural frequency decreases and the impulse response speed increases with more mass, but that is not relevant in your case.
I think you should go with what you planned with 2x22 chipboard and at least one row of noggings in the middle to connect the beams for twisting and some load distribution.
22 K-plywood is stiffer but much more expensive than 2x22 chipboard. The slight increase in weight can even be beneficial as it becomes harder to excite the mass. However, the natural frequency decreases and the impulse response speed increases with more mass, but that is not relevant in your case.
I think you should go with what you planned with 2x22 chipboard and at least one row of noggings in the middle to connect the beams for twisting and some load distribution.
45x220 c/c 300 joists should, as far as I can see, meet all requirements regarding bound utility loads and moving point loads. However, it's certainly no disadvantage to have a row of noggings in the middle with the same timber dimension as the beams. Deflection and flex are not absolute states but also depend on personal feelings and taste. Many people, including myself, prefer floors that are significantly rigid. Two layers of 22 mm chipboard may be an engineer's dream, but definitely not an architect's dream. 44 mm plus an overlay floor of perhaps 15 mm means that 59 mm is lost from the planned room height, which is not entirely negligible. Two layers of 22 mm chipboard cost about 180 SEK per sqm, and one layer of 21 mm k-plywood is about 200 SEK per sqm. Additionally, chipboard is a more questionable building material than plywood, with a significantly higher glue content. In a passive house, this can be of some significance. Personally, I would never use chipboard in a living space. When it comes to the sound-reducing ability of different floor constructions, the need must be formulated based on the intended use. The chipboard solution may be better in some cases and worse in others.
Interesting discussions. I'm poring over them in my silence without really knowing what I should contribute.
I'm thinking like this:
1) Corridor
It's now two halves with a span of about 4 meters each. The construction is about 12 meters long and a certain path here will probably function as a corridor. It starts with the front door and hallway and in a straight line forward, one can access half of the house's functions. I wonder if I should further reinforce straight in this corridor. I don't know what is smartest, to add nogging there, at several points, or to insert one or two more 220x45 joists, so that it's cc 150. It's less work to insert two extra joists than to nog at, for example, 5 points, at least equivalent work.
2) Nogging in general
I can absolutely consider putting nogging in the middle of the span on both sides of the floor, so it's about 2 meters on each side. What I'm worried about is that it will become uneven due to the nogging, meaning they end up 1mm too high, creating a lot of problems when laying the chipboards. It feels like it's easily done. Right now, there's an uneasy feeling suggesting it would be wise (but oh so cumbersome) to cut the height of all noggings by 1mm first, so one can be quite sure they won't interfere with the rest of the floor. But on the other hand, that would mess up the possibilities to screw the chipboards into them, but maybe it doesn't matter if they're a bit low.
3) The floor will be chipboard, with 22x70 and finally something parquet-like (tile in some parts)
I understand that chipboard might not be the optimal material, but the floor has been purchased over a year ago. At least most of it. Right now it feels a bit off to get rid of around 60m2 of boards, just because one thought of something smarter.
But it will be like this: 1 layer of chipboard and on top of that 1 layer of 22x70 or similar, which I then lay the underfloor heating pipes in. These 22x70 probably won't make the floor particularly more stable, but at least one can lay it so that it crosses the joist structure, or the chipboards in a well-thought-out way.
On top, there will be self-leveling compound + tile in the bathroom and hallway.
That's my thinking now. But I'm prepared to adjust my plans until the last minute.
The area we've been looking at appears roughly like this in the underfloor heating project. At the top, you see the main entrance, which then runs straight down and continues in an equally large volume below that's off the image.
You can also discern a "corridor" from left to right, roughly in the middle of the height, which leads to the bedrooms on the right edge. But there will be no significant bounce here, because now one walks on the greatly oversized laminated beam, which is very rigid. The floor next to the beam feels very rigid now, despite the chipboards just being loosely laid there.
Thank you for trying to sort everything out!
I'm thinking like this:
1) Corridor
It's now two halves with a span of about 4 meters each. The construction is about 12 meters long and a certain path here will probably function as a corridor. It starts with the front door and hallway and in a straight line forward, one can access half of the house's functions. I wonder if I should further reinforce straight in this corridor. I don't know what is smartest, to add nogging there, at several points, or to insert one or two more 220x45 joists, so that it's cc 150. It's less work to insert two extra joists than to nog at, for example, 5 points, at least equivalent work.
2) Nogging in general
I can absolutely consider putting nogging in the middle of the span on both sides of the floor, so it's about 2 meters on each side. What I'm worried about is that it will become uneven due to the nogging, meaning they end up 1mm too high, creating a lot of problems when laying the chipboards. It feels like it's easily done. Right now, there's an uneasy feeling suggesting it would be wise (but oh so cumbersome) to cut the height of all noggings by 1mm first, so one can be quite sure they won't interfere with the rest of the floor. But on the other hand, that would mess up the possibilities to screw the chipboards into them, but maybe it doesn't matter if they're a bit low.
3) The floor will be chipboard, with 22x70 and finally something parquet-like (tile in some parts)
I understand that chipboard might not be the optimal material, but the floor has been purchased over a year ago. At least most of it. Right now it feels a bit off to get rid of around 60m2 of boards, just because one thought of something smarter.
But it will be like this: 1 layer of chipboard and on top of that 1 layer of 22x70 or similar, which I then lay the underfloor heating pipes in. These 22x70 probably won't make the floor particularly more stable, but at least one can lay it so that it crosses the joist structure, or the chipboards in a well-thought-out way.
On top, there will be self-leveling compound + tile in the bathroom and hallway.
That's my thinking now. But I'm prepared to adjust my plans until the last minute.
The area we've been looking at appears roughly like this in the underfloor heating project. At the top, you see the main entrance, which then runs straight down and continues in an equally large volume below that's off the image.
You can also discern a "corridor" from left to right, roughly in the middle of the height, which leads to the bedrooms on the right edge. But there will be no significant bounce here, because now one walks on the greatly oversized laminated beam, which is very rigid. The floor next to the beam feels very rigid now, despite the chipboards just being loosely laid there.
Thank you for trying to sort everything out!
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How can you see this? I agree that deflection is a condition experienced differently from person to person, however, there are deflection requirements in the standard (law) that should be met. Since the founder of this thread wanted double joists and asked about noggings, I answered the question he asked.
Out of pure curiosity, in what way does joists have a certain significance in passive houses?
Out of pure curiosity, in what way does joists have a certain significance in passive houses?
Construction veteran
· Åland
· 2 067 posts
Oh, seems like a lot of material waste from start to finish in this construction. Hope there will be room for insulation too.
TS seems to like stable stuff. I would have placed a 45x195 under the joist along the glulam beam screwed into the glulam. I personally wouldn't have liked having the joist hanging in joist hangers. Even if the longitudinal beam is intended to be visible, I would have done it. If it had been from the start, I would have chosen an HEA steel beam to splice in, then you can secure it even better and completely hide it in the floor (with the help of a constructor, of course..)
Absolutely, it should be stable things, you've understood me right.leby said:
The beam hangs down about 15 cm or something and becomes visible on one side, in the other direction it becomes a box when some pipes are pulled, etc. On the built-in side, which is also the most loaded, I can absolutely put a beam underneath. The question is, purely structurally, what difference such a beam makes. I think each joist now has about 6 anchor screws each (6 * 40 = 240 pcs) and what difference it will make if there's an added beam with, well, 20 screws, maybe 6x100mm or something. I don't see that it should make things particularly much stronger. Or maybe I'm completely wrong.
What do you mean by that? Sure, it was early in the morning, but that was a comment similar to a teenager's. Can you point out something specific that's wasteful? "from start to finish"... wowseniorkonsult said:
Construction veteran
· Åland
· 2 067 posts
More faults with wise teenagers than with sleep-deprived amateur builders?
Now it seems that the joist has already been installed, but, according to my opinion, c 600 is sufficient for this construction if the highest quality grade of lumber is chosen, plus nogging in two rows. This is entirely in accordance with accepted standards. If quality lumber happens to be unavailable, you can use 70x220 mm c 600. A screw-laminated particle board on this provides an excellent stiff box construction. Even if the board doesn't fit due to underfloor heating plates or the equivalent, the joist is still considered to handle the deflection. I assume the double particle boards are for the underfloor heating.
Ceiling with double gypsum, I assume, is due to sound insulation. Otherwise, I don't understand why double. A reinforcing sparse panel on the underside is also added here.
Oops, sorry, just saw that I had old technical data regarding the loads. 4.2 m for 45-ers on 600 becomes insufficient.
Now it seems that the joist has already been installed, but, according to my opinion, c 600 is sufficient for this construction if the highest quality grade of lumber is chosen, plus nogging in two rows. This is entirely in accordance with accepted standards. If quality lumber happens to be unavailable, you can use 70x220 mm c 600. A screw-laminated particle board on this provides an excellent stiff box construction. Even if the board doesn't fit due to underfloor heating plates or the equivalent, the joist is still considered to handle the deflection. I assume the double particle boards are for the underfloor heating.
Ceiling with double gypsum, I assume, is due to sound insulation. Otherwise, I don't understand why double. A reinforcing sparse panel on the underside is also added here.
Oops, sorry, just saw that I had old technical data regarding the loads. 4.2 m for 45-ers on 600 becomes insufficient.
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It is clear that one should follow the prevailing standards. However, doing so does not guarantee a result that one is satisfied with. All standards are compromises between the desirable and the possible. Wooden floor joists can feel insufficiently rigid, even though they meet all the standard requirements. I got involved in this discussion because I reacted to the fact that the 45x220 joists were hung in joist hangers instead of resting as continuous beams, spliced over the support beam of laminated timber. tobbew has explained the reason for this, but I still believe that the project would have benefited from a different design. A lot of timber has been used without achieving a perfect solution.
The airtightness requirements recommended for newly built houses in general are mandatory for passive houses. This makes the reliance on a well-functioning ventilation system extremely high. It therefore becomes important to monitor emissions from the included building materials. Particleboard is a problematic material in this regard. Among other things, they release formaldehyde, admittedly below the limit value, but still.
The airtightness requirements recommended for newly built houses in general are mandatory for passive houses. This makes the reliance on a well-functioning ventilation system extremely high. It therefore becomes important to monitor emissions from the included building materials. Particleboard is a problematic material in this regard. Among other things, they release formaldehyde, admittedly below the limit value, but still.
It's an attempt at a passive house (we should end up close at least) and the ventilation will be FTX, so that part should sort itself out. But that's an aside.justusandersson said:
I don't know how much the construction is weakened by using joist hangers instead of having the joists rest on top. I think it shouldn't matter as long as the joist hangers stay in place. I mean, the joist has exactly zero deflection in its hanger. So the span is even shortened by almost a decimeter, if we're being precise. Then if each joist is now held by 6 screws (can't remember), we can load a joist with the force that 6 screws can bear. Which might be less than what would break a joist, I can't answer that, but is this a weak point?
Or what am I missing there?
However, I do understand the insecurity of the whole construction relying on a bunch of screws staying in place. I can see why someone might dislike that, compared to resting on something. But as someone suggested a few posts up, I can indeed, on the glulam beam, press a fairly thick joist up under the joist hangers so that the joists rest on, for example, a 45x170 or something like that, which I can screw-laminate into the beam. If you think that would be better. I myself have no direct opinion.
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But standard is still a minimum requirement, right? But if you find the EKS "hard to read", I understand that there can be some personal opinions. I also like comments that talk about how one "should have done" instead of discussing the current situation.
Here you can find dimensioning tables for joist hangers if you want to double-check your fastenings. http://www.bkl.lth.se/fileadmin/byg...tur/Beslagshandbok_2012_Gunnebo_Fastening.pdf
You have about 2.5kN per fastening.
Don't forget the potential fire protection of these.
Here you can find dimensioning tables for joist hangers if you want to double-check your fastenings. http://www.bkl.lth.se/fileadmin/byg...tur/Beslagshandbok_2012_Gunnebo_Fastening.pdf
You have about 2.5kN per fastening.
Don't forget the potential fire protection of these.