Building out loft with steel beams

[MaxFalk]

hello!

I'm moving into an apartment that already has a loft. However, I would like to extend the loft over an area of about 5x4 meters. The 5-meter walls are load-bearing concrete walls.

My first thought was to use 145x45 timber beams with 40 cc spacing, but I understand that the area is too large for it to be stable without some support in the middle. I don't have room for 220x45 beams. So, I'm considering using steel beams instead but can't find any recommendations on what cc is suitable if I use, for example, 80 mm I-beams. Or could rectangular steel tubes also work? Does anyone have experience with this?

Then I wonder what is the best way to attach the beams to the load-bearing walls on the long side? Would a wooden stud of 70x45 be enough?

Thanks for all the tips! I find it difficult with the material choices!

 

[justusandersson]

I assume the floor span is 4 meters. To achieve acceptable deflection conditions in the loft without central support, glulam or steel is required. An HEA beam placed at c/c 600 mm needs to be of the type HEA 120. This becomes very expensive and heavy. Glulam beams 140x180 can handle it. You can reduce the height somewhat by increasing the width.

The load on one end of a beam will be about 300 kg. It's probably fine to use 45x70 joists as long as they are properly anchored. But it requires quite a few expansion bolts.

 

[MaxFalk]

Thank you!!

This is not easy. It helps a few steps in the right direction.

I assume that the span of the floor structure is 4 meters. To achieve acceptable deflection conditions in the loft without central support, glulam or steel is required. An HEA beam on c/c 600 mm needs to be of the type HEA 120. It becomes very expensive and heavy. Glulam beams 140x180 can handle it. The height can be reduced slightly by increasing the width.

The load on one end of a beam will be about 300 kg. It will likely work fine to use 45x70 studs as long as they are properly fastened. However, quite a few expansion bolts are required.