Time to start looking for/ordering lumber for the spring projects: We're going to tear up a poorly built/bad/rotten floor in an insulated old outbuilding that will become a small pub. Considering dimensions for the floor joists. When we changed the living room floor construction from "mullbänk" to joists on piers, the joists were 45x195 and the beams 150x150. No one calculated the dimensions, we just took robust—and expensive—lumber. Now that I read around a bit, I see many use 45s even for beams? Will that hold? The floor isn't going to be loaded more than normal (possibly we'll install a small stove, but it should weigh a maximum of 100 kg).
A cheaper and more manageable option, but this time my father-in-law is going to help, and he will mutter about "women’s construction and house of cards" if I don't have very strong arguments (he obviously knows best in all situations, and since he is kind enough to help, I'll just have to grin and bear it...).
A cheaper and more manageable option, but this time my father-in-law is going to help, and he will mutter about "women’s construction and house of cards" if I don't have very strong arguments (he obviously knows best in all situations, and since he is kind enough to help, I'll just have to grin and bear it...).
The bending strength is mainly due to the height of the beam, i.e., might a 220x45 standing on its side be stronger than a 150x150. Now, I don't really know if that's the case, I'm just trying to illustrate how it works. With a bit of luck, someone with good literature will look this up in a table so we get an answer. ...
But if you really want to dimension correctly, you should probably have your construction calculated.
You need to know the spans between the supports for the beam, probably the span of the joist as well, and what load the floor is supposed to bear... and stuff like that, you know....
But if you really want to dimension correctly, you should probably have your construction calculated.
You need to know the spans between the supports for the beam, probably the span of the joist as well, and what load the floor is supposed to bear... and stuff like that, you know....
OK, sounds reasonable. One advantage otherwise with 150x150 should be that they stay in place more easily during construction? 45s sound flimsy even though I understand that it's primarily the height of the support beams that determines sturdiness. Calculating, I don't really know if I will do it (=let someone else knowledgeable in construction do it) in this case. I'll go with the normal cc 600 and instead use larger dimensions - it will certainly be better than what's there today... It's also a fairly small floor, so the cost will probably be reasonable anyway.
If one can and wants to bolt together 4 pieces of 45x220 to get a homogeneous beam of 180x220 to the eye, what does that correspond to?GustavW said:
Or 2 pieces of 125x125 side by side or alternatively on top of each other?
Apart from the price, which solution provides the stiffest beam?
The stiffness increases linearly with width and quadratically with height, meaning l*h^2.
A 180*220 is thus as strong as a 90*315 glulam provided you have achieved the jointing.
Two 125*125 on top of each other glued/screwed together provide a construction that has 80% of the strength of the above.
Two of the same next to each other give 30% of the same strength.
A 180*220 is thus as strong as a 90*315 glulam provided you have achieved the jointing.
Two 125*125 on top of each other glued/screwed together provide a construction that has 80% of the strength of the above.
Two of the same next to each other give 30% of the same strength.