Dimension for a beam in the attic

[Saxpy]

I am going to spray eco-fiber in the attic, so I need to build a walkway to access it and check for moisture, etc.

The span of the trusses at the correct height is 270cm and they are placed at 75cm centers.
I was planning to attach a beam to the truss and then lay regular rough planks (just over 20mm) as the floor.

What size beams are appropriate for that span? It is not for storage, just to be able to come up and inspect.

 

[Mats]

I would guess that it holds with regular 22 floor chipboard without the support of joists if you splice on the rafters. Otherwise, you can take, for example, 125X38 and nail lying down as a walkway and skip the raw board.

 

[andersmc]

I have used 90x45 studs and they are stable enough. If you also have only 75 between the trusses, it becomes even more stable. I also have 22mm untreated wood paneling, but it would have been quicker to lay particle board. It depends on how easy it is to access. It can be tricky to lift particle board sheets up a loft ladder. Building something directly on the trusses is probably not interesting; you want to be half a meter up from the "floor" (meaning the ceiling).

 

[Saxpy]

No, not directly on the rafter, they will be 60cm up from the bottom of the rafter, that's why I have to add battens. Maybe try a 90x45 and see if it works.

 

[ByggaNytt]

Raw boards between (~120 cm) the chairs work well too!

http://www.familjenlindstrom.se/images/byggahus/stomme/kryp.jpg
http://www.familjenlindstrom.se/images/byggahus/stomme/isolering/losull/losull_2.jpg

 

[andersmc]

Now it got a bit OT but ByggaNytt, what kind of wind deflector do you have? The one visible in the first picture.

 

[ByggaNytt]

See previous threads here:

http://www.byggahus.se/forum/isolering/50421-luftspaltsbildande-cellplastskivor.html
http://www.byggahus.se/forum/415477-post7.html