Install a walkable ceiling, thickness of the rafter wood

hello,

I would like to briefly introduce myself since this will be my first and maybe not the last post in this forum.

I come from rheinbach in germany, which is near bonn. I am 41 years old and am renovating or currently renovating a half-timbered house. right now the whole ceilings are being torn out because the ceiling height is not good :) and I am too tall :) however, my question actually concerns the roof truss first. I want to install a walkable ceiling where later floor installation panels osb 22 mm thick will be laid/screwed on. the beams will either be laid in joist hangers or directly on the half-timbering on the right and left, the length of the beams will be about 4.5 m.

my question now is how thick must the squared or rafter wood be? is a beam of 15 x 15, for example, or rafter wood 8 x 16 or less enough?? what is the minimum? the area should not be made livable, only walkable. or is this difference not big walkable/livable meaning in the sizing of the beam?

thank you very much for the help

How is it only walkable? i.e. you don't want to put anything down there? but just "walk around"? or how should that be understood? :confused:

hello,

yes, otherwise I would have said storage room. but I have already been able to find out something. a carpenter told me the bearing length x 0.5 would mean in my case a beam of 8 x 20 x 4m or 4.3 m with the bearing.

best regards

Hello SuperHorst,
A walkable ceiling is a load-bearing component; this modification to the building requires approval in NRW.

You should therefore consult a structural engineer and have the beams (and fastenings!) calculated – even if the carpenter's experience leads to seemingly good advice at first glance. The span of 4m is not necessarily easily manageable for wood, a glued laminated beam may be necessary (as mentioned: consult a structural engineer).

hello,

I don't quite understand. There are oak beams spanning 5.5 m, a total of 4 pieces, with loam and wood in between, where I would estimate the weight at about 1.5 tons without the beams. The beams themselves are 12 x 15. Now I wanted to go and lay the wood in the opposite direction because that way I have less span and triple the number of beams with 8 x 20 x 4 m, and now I should be concerned about the structural engineering? seriously??
I know what I'm doing, I will put the old beams back in and smear the loam in between again and paint the whole thing.

Regards

As I said, Superhorst, ceiling beams are load-bearing components > Landesbauordnung=law, seriously; it will probably be the case that the whole thing supports, but it still must be calculated according to the law.