Dimensioning Intermediate Floor

[Erik_D]

I need help sizing an intermediate floor.

The span is 5.50 free bearing.
I would prefer not to exceed 235 mm in height. Any suggestions?

 

[jon_h]

You'll manage with 45x220. I would have used c/c 300 with such a long span.

It's also good if you have floor particleboard glued to the joists, as it creates a composite construction that makes the floor more rigid.

 

[Erik_D]

Are you sure??

Yes, I found a table on the internet and it indicated 4.5 as the maximum span for 45 * 220

 

[ByggaNytt]

I have a span of 450 with 45*225 Kerto at c/c 60 which feels stable with glued floor chipboard + double rows of noggings!
550 is a looong span....

http://www.familjenlindstrom.se/images/byggahus/bygget/bygg_2.jpg
Moelven Töreboda AB - - Kerto-S

Sizing program:
Moelven Töreboda AB - Program

 

[ByggPutte]

Should it be construction timber?

Best regards, Putte

 

[jon_h]

Actually, you don't want wooden beams made of regular construction timber to span more than five meters, especially due to how the beams handle dynamic loads, such as the slight swaying of the floor when someone walks across it. However, static loads are a completely different matter, and you can significantly reduce the figures from the tables for carrying weight.

But to speak about your case, if you have glued and screwed 22 mm chipboard as a subfloor and have placed the beams at 30 c/c, you will get a sturdy floor with 45x220 at a 550 cm span. You can also add cross-bracing to further strengthen the rigidity of the beams.

By the way, what are you building, is it a new construction or are you reinforcing an existing attic floor?

 

[jon_h]

Should be construction wood?

Best regards, Putte

Don't know if you just accidentally wrote the question mark there, but anyway. It should of course be construction wood, C24. (Or C30..)

 

[ByggPutte]

It was a long time ago that I worked with graded timber. Back then, I think it was called T24.

Best regards, Putte

 

[ByggaNytt]

According to the program above, it should be:

c/c 600 -> 56*270 LimTrä (deflection 1.4 mm)
c/c 600 -> 45*300 Kerto S (deflection 1.3 mm)

This assumes glued chipboard flooring!
I am not a designer...

 

[jon_h]

Wasn't the T classification from T0-T3? And then we also have the K classification, but it was just directly translated by replacing K with C...

 

[ByggPutte]

Yes, I said it was a long time ago .
When we built a planing mill for a smaller building materials
company, the owner took a grading course.
After he finished, he stamped wildly on
just about everything .

Best regards, Putte

 

[jon_h]

Hehe, he was a little proud there..

 

[Toy]

We will have a 5.6 meter span with 45*300 kertobalkar at cc40 and glued 22mm floor chipboard to prevent any deflection. This has been calculated by the house manufacturer.

Best regards, Tommy