Hello.
I have a floor structure for the upper floor with various spans, consisting of 45x220 K24 cc600.
The longest free span is 3.8 meters, which is between the outer wall and the load-bearing wall, so the entire floor joist length is (slightly) double that.
The next longest free span is 2.4 meters. But the beams are actually 4.3 meters between the outer wall and the load-bearing wall, though they hang on the support legs and a relieving beam at 1.9 meters from the outer wall, see the image.
So, from the outer wall, 1.9 meters into the house, the subframe "hangs" in the rafters on the support legs, and the beams in between are attached with fork anchors to a 45x220 that is supported from the relatively stable point at the support legs. Then there is a remaining 2.4-meter span to the load-bearing wall.
Then I actually have a 2.5-2.6 meter free span in another spot as well, between two load-bearing walls.
How much do you think I should sheet? Only in the 3.8-meter section, or in all?
I have a floor structure for the upper floor with various spans, consisting of 45x220 K24 cc600.
The longest free span is 3.8 meters, which is between the outer wall and the load-bearing wall, so the entire floor joist length is (slightly) double that.
The next longest free span is 2.4 meters. But the beams are actually 4.3 meters between the outer wall and the load-bearing wall, though they hang on the support legs and a relieving beam at 1.9 meters from the outer wall, see the image.
So, from the outer wall, 1.9 meters into the house, the subframe "hangs" in the rafters on the support legs, and the beams in between are attached with fork anchors to a 45x220 that is supported from the relatively stable point at the support legs. Then there is a remaining 2.4-meter span to the load-bearing wall.
Then I actually have a 2.5-2.6 meter free span in another spot as well, between two load-bearing walls.
How much do you think I should sheet? Only in the 3.8-meter section, or in all?
Under the heading "stiffening":
http://www.traguiden.se/TGtemplates/popup1spalt.aspx?id=1252&contextPage=5955
the need for cross bracing is stated for spans between 3 and 4 meters.
But I would really like to get some second opinion... I really want to avoid a wobbly floor.
Then I don't know what significance the extra weight added has? It's probably not good, but on the other hand, it might be such a minimal disadvantage that it's not worth worrying about...
http://www.traguiden.se/TGtemplates/popup1spalt.aspx?id=1252&contextPage=5955
the need for cross bracing is stated for spans between 3 and 4 meters.
But I would really like to get some second opinion... I really want to avoid a wobbly floor.
Then I don't know what significance the extra weight added has? It's probably not good, but on the other hand, it might be such a minimal disadvantage that it's not worth worrying about...
Without knowing too much about the construction techniques here, I would strap on "all" places, maybe even add another beam so it becomes 30cc... 3.8 must be on the edge, right? How much deflection have you calculated? About 2.0?
cc600 should not be any problem. I would have placed noggings at cc600. If you then glue and screw the chipboard on top, it will be fine.
What do you mean here?hokanp said:
Are you thinking, for example, of 5 noggins if the span is 3 meters, as an example ...
Well, I haven't calculated anything.Danneå said:
But I went through the blueprints and documents and found the deflection calculation that a 1kN point load gives a deflection of 1.23 mm in the longest section (which is actually only 3424mm according to the drawing).
My previous statement of 3.8 meters was just carelessly measured on-site, where I didn't really have a 100% grasp on where the load-bearing wall actually was. :blushing:
Ultimately, I chose to place only one row of kortla on my longest span (just over 3.4 meters).
View attachment 44105
It immediately felt how the floor became more stable and the flex decreased.
I won't get a final answer on how everything turned out this winter, as the chipboard floor will be glued no earlier than next summer.
View attachment 44105
It immediately felt how the floor became more stable and the flex decreased.
I won't get a final answer on how everything turned out this winter, as the chipboard floor will be glued no earlier than next summer.
Last edited by a moderator:
A very effective method for solving the problem of long spans is to screw glue boards on both the top and bottom sides. Plywood is best, but OSB and chipboard also work.
Is it possible to get rid of possible 'floor creaks' by cross-bracing the joists?
I have a creaky floor in the living room with a basement underneath, the joists rest on a beam in the middle with about a 3m span on each side of it.
No cross-bracing there though - but it's open up in the joists so all possibilities exist before a ceiling is nailed down there.
I have a creaky floor in the living room with a basement underneath, the joists rest on a beam in the middle with about a 3m span on each side of it.
No cross-bracing there though - but it's open up in the joists so all possibilities exist before a ceiling is nailed down there.
Mikael_L, I have roughly the same conditions as you.
On the ground floor, I have a span of 3.5m on both sides of a steel beam. There, I have added blocking in the middle on each side. The ground floor has the highest requirements, as that is where most activities will take place, and a bathroom will also be built.
On the upper floor, I have spans of 4m and 3m. There, I have only added blocking in the 4m section. Only bedrooms, and I don't consider the requirements for flex to be as high.
On the ground floor, I have a span of 3.5m on both sides of a steel beam. There, I have added blocking in the middle on each side. The ground floor has the highest requirements, as that is where most activities will take place, and a bathroom will also be built.
On the upper floor, I have spans of 4m and 3m. There, I have only added blocking in the 4m section. Only bedrooms, and I don't consider the requirements for flex to be as high.
Yes, I feel satisfied now, it's probably the future bedroom, which is likely more forgiving than the rooms you spend time in during the day. And already now I find the beam layer on the verge of sufficiently stable everywhere, even before the chipboard is screwed and glued (I have laid out chipboard loosely on top of the beams right now).
FredrikR, I have no clue about the creaking question ... But if it moves less then ...
FredrikR, I have no clue about the creaking question ... But if it moves less then ...
I had pretty much the same conditions and made the same solution. I also noticed a clear difference when I jumped around on the beams. However, I placed the floorboards directly on the beams - which, as far as I know, doesn't provide as stiff a floor as building up with screw-glued particle board. In retrospect, I would probably have added noggin beams in 2 rows. Such a small cost/work overall when doing a floor change.Mikael_L said:
I read around here and there and was initially considering cross-bracing. My carpenter (whom I have great trust in) warned me against it. His experience is that it can become 'too' strong and create a wavy floor depending on how the floor is loaded. In contrast to nogging where you distribute the weight more so that more beams have some deflection decreasing from the point of load.