Advice on floor structures

[erik_m_a]

Hello! We are planning an extension of about 6x5m, crawl space and 1 floor, gable roof. However, we need advice regarding the floor joist. Our engineer initially designed a pillar in the middle of the crawl space, where a laminated beam would rest, to support the floor joist. Since we want some storage space in the crawl space, we desired a "clean surface," so the engineer instead suggested a HEA beam weighing 300kg (see image).

However, the builder has another suggestion, partly because it will be incredibly difficult to get the HEA beam in place (can't be lifted in with a crane truck), namely to build the floor joist with KERTO beams. See image. What do you think about this option? It might be more expensive, but it feels appealing otherwise...? According to Träguiden, a KERTO beam of dimensions 45x300 can span up to 5 meters.

Incredibly grateful for all input!
Best regards, Erik

 

[Huddingebo]

It's all about meeting the requirements for maximum allowed deflection/sway in the floor. There are many alternatives and pros and cons. You have to calculate it. Is it a 5m span? That is, 5m between the inside of the foundation walls? I have 4.8m and chose to construct the joists with standard 45x220 with 30cm on center and 1m between the shorter beams. I thought it seemed the most convenient and resulted in minimal waste. When I jump on the floor, it feels solid.

 

[erik_m_a]

Thank you!
It is probably not more than 430 cm actually, from inside foundation wall-->foundation wall.
With kortlekar, do you mean kortlingar? Like:

 

[Huddingebo]

Yes, exactly, noggins. The phone messes up the words sometimes.
Okay, 4.3m doesn't require any advanced solutions. It's a common length. Do what is cheapest. Are you going to insulate yourself?
With odd CC, there's a lot of work with the insulation knife.
There are templates online that indicate deflection for different spans depending on how tightly you frame.
Perhaps 45cm is enough in your case, and then there should be standard insulation, I believe.

 

[olofh]

Do you even need a beam in the middle? With a beam, you get a span of just over 2m, should it be a very flimsy framework?

 

[erik_m_a]

Do you even need a beam in the middle? With a beam, you'd have a span of over 2m, is it going to be a very light framework?

No, it won't be light. I was also a bit questioning about the beam, it sounds like it's unnecessary then.

 

[justusandersson]

It's not possible to solve the joists with regular construction wood 45x220 C 24 without a central beam. Not even if it's placed at c/c 300 mm. The alternatives are glulam or Kerto-beam. The smallest glulam option is 42x270 c/c 600 with screw-glued floor chipboard. Such a glulam beam probably costs over 500 SEK each. I don't have basic data on Kerto-beams, but looking at their brochure, 45x260 c/c 400 with screw-glued chipboard should suffice. Personally, I would go up one step in dimension for both glulam and Kerto to avoid screw-gluing. The advantage of glulam and Kerto (as far as I remember) is that you order them in the correct length, so you avoid waste.