Self-supporting roof trusses, load-bearing wall?

[Addelin]

I have a single-story house and am going to demolish a 4-meter wall. Now the building permit states that the roof trusses are self-supporting. But a wall that runs across the house is framed with cc30 45x70, and at the top, there is a 70x120 beam horizontally. This makes me think it is a load-bearing wall. Other walls running in the opposite direction are framed with cc60 and 70x45, both standing and lying against the ceiling. So in my view, the wall with 70x120 is load-bearing?

Isn't the whole idea when roof trusses are self-supporting that no load-bearing walls are needed in the middle of the house?

 

[hempularen]

Well, it could either be that the truss construction has been changed, so the information in the building permit is incorrect. Or a "semi-loadbearing" wall has been made to get some safety margin, and to reduce deflection of the roof.

Try to get someone to assess the trusses.

 

[Kallebo]

Can't you post a picture of the rafters? It's possible that they built the wall for another reason than making it load-bearing..

 

[Addelin]

Can't you post a picture of the roof trusses? It's possible that they built the wall that way for some reason other than making it load-bearing..

The roof trusses are cc 120 and approximately 6 meters long with a very low slope, hard to capture in a picture. But I also made a rough paint sketch of how they are built.

 

[justusandersson]

If the trusses look like that, they should be self-supporting. But to say for sure, you need to know the cross-sectional dimensions of the different components as well as the span. Preferably the roof pitch too.

 

[Addelin]

My spontaneous thought is to put a 4m HEA 180 beam where I'm tearing down the wall, so I should be completely on the safe side whether the wall is actually load-bearing or not. What do you think about that?

 

[justusandersson]

Personally, I think it's a somewhat backwards reasoning. It can't be particularly difficult to determine if the need exists. Do you have any basis for that sizing, or do you just happen to have a 4m long HEA 180 lying around at home? It's always problematic to mix steel into wooden structures, even if it is sometimes the only solution.