Difference between C24 and C30?

[Mogg]

I am going to buy 45x220 studs and choosing between C24 and C30. According to the design tool, I should use the higher strength, but is there really any difference in practice?

 

[justusandersson]

Yes, there is a big difference. C30 has 25% higher bending strength than C24. Depending on how you plan to use the studs, the difference can be crucial. For example, C30 timber can handle a longer span when used as floor joists.

 

[Mogg]

Yes, there is a big difference. C30 has 25% higher bending strength than C24. Depending on how you plan to use the studs, the difference can be crucial. For example, C30 timber can handle longer spans when used as floor joists.

Wow, is the difference that significant..!!
It is going to be for a roof with a span of 4.1m and a 20-degree slope.

 

[justusandersson]

Which dimension are you going to use? (Cross-sectional measurements, that is).

 

[Mogg]

What dimension are you planning to use? (Cross-sectional measurements that is).

I'm not sure if I understood you correctly, but the beams will be 45x220 with cc60.

It seems difficult to get c30 and I guess they are made-to-order? Do you get straight beams/joists if you place such an order? That depends on where you order from, of course..

The next problem will be to get hold of these.

 

[Mogg]

Now I have measured the extension once again and obtained;
Width (which the roof beams shall span over) 4.18m
Roof pitch 17 degrees
Cc60

And according to the calculation program, it should suffice with c24 in the dimension 45x220

 

[Mogg]

It's calm now, because it has been resolved. Went on a reconnaissance round today and found dry, perfectly straight studs!!!

 

[justusandersson]

For a roof with a span of 4.1 m in Skaraborg (snow zone 2 if it's not on Billingen), 45x220 C 24 c/c 600 mm is sufficient. C 30 timber provides less deflection in the middle.

 

[Mogg]

For a roof with a span of 4.1 m in Skaraborg (snow zone 2 unless it's on Billingen), 45x220 C 24 c/c 600 mm is sufficient. C 30 wood gives lower deflection in the middle.

Yes, I'll go with c24!