I am planning an extension according to the attached image (existing house not shown). What dimension might be needed for the two red beams I've drawn by the stairs? I'm guessing glulam. The intermediate floor I am thinking is C24 45x220 and 570cm long from wall to wall. Upstairs will be a bedroom. I assume I still need a structural engineer with calculations to present with the building permit, but I would like to get it as right as possible myself first.
1. The long beam to the left of the stairs will be about 705 cm long. It is not centered, resulting in a span of 245 cm on one side and 325 cm on the other.
2. The short beam to the right of the stairs will be 330 cm. This can, however, be more freely placed, such as in the middle of the 570 cm long floor joist.
A 7 m long glulam beam needs to have the dimension 165x540 mm or equivalent. I think you should contact a structural engineer first. I don't think it's a sufficiently stable solution that you have sketched, as I can understand it from your image.
Okay, it was a bit stronger than I thought. Maybe a steel beam instead then? That was what I had planned from the start, but then I thought glulam would be enough after reading some other threads...
What do you mean by a sufficiently stable solution otherwise?
Edit: addition that I went with the wood guide that says up to 7 meters with 45x220 so I think less than 6 meters that I have should be okay.
45x220 beams that are 5.7 m long with support in the middle from a beam work perfectly well. A house that is 11-12 m long needs lateral stability in the form of cross walls and the like. From that perspective, a 7 m long beam is too long, regardless of whether it is made of glulam or steel. If you make the beam 5 m long, 215x360 is sufficient if you want it as low as possible.
Do you mean like the green wall I made now? My thought is that the first part is a basement on the ground/garage and then on the other side of the stairs becomes a more regular room. It should be possible to do like all other garages where a car should fit, right? So a wall needs to be added, but it will still be 7 meters away (I hope).
Now, I'm not going to drive in a car daily, but I would still like those dimensions, which makes 5 meters too short.
Just curious, the beam must rest on something. Did you mean in the first case that I might have only had a post down then?
It is also possible to make another wall on the other side of the stairs, but it might not be of any use on that side anyway, and the problem is the 7-meter side. Or a wall is going to be there regardless, but I was thinking otherwise a regular non-load-bearing one.
At the front/gate where there is a wooden wall, I understand that it must be supported by its own post. Just inside the outer wall, I was thinking.
But if the wall by the stairs were made of something like lightweight concrete/lecablock, can't it just rest on these? Too weak for the point load that 7 m gives? If you first have something stronger horizontally at the top between the beam and the lecawall?
A future engineer might have to specify this later, but I would like to know.
