Safe roof construction, or misunderstanding?

[ninjaman]

Hello!
We are in the process of doing a roof lift/addition of a floor and we recently received the construction drawings. I have no knowledge whatsoever about construction, drawings, or building and am entirely dependent on the professionals.

However; when I look at the drawings, I get the feeling that either I or the designer has missed something. I thought (perhaps in my naivety) that a construction drawing would essentially explain the structure of the roof. We have been clear that we also want solar panels on the roof, which I assume is a significant load. But how can this hold? The floor looks sturdy, but the roof? About five degrees, 8m span with 45x195 C24 with 1200cc...

Have I misunderstood everything? My common sense tells me that it can NEVER hold, or am I completely off? Thankful for help!

 

[witten]

Oh no, that won't hold. Ångspärr is missed too.

 

[witten]

I must bring to your attention that they have designed a single-stage sealed facade as well... A completely condemned construction solution.

 

[ninjaman]

Oh no, that won't work. Vapor barrier is missed as well.

I think the vapor barrier is listed as "folie" in the top drawing. But as I said, I know nothing about this...

 

[Rickard.]

It is well drawn trusses with a 45x195 as the top chord? As it is drawn, they only need to support ≈1/3 of the span. How the trusses should be dimensioned is something the manufacturers are really skilled at.

 

[ninjaman]

It is drawn trusses with a 45x195 as top chord? As it is drawn, they only need to handle 1/3 of the span.

Shouldn't the construction drawing include trusses or calculations? What will support the truss? As I said; Nothing in this is obvious to me...

 

[witten]

Yes, it might be intended that way and drawn a bit unclearly. But then timber quality shouldn't have been specified since the truss supplier determines that. What about the floor joists? Is there a wall where there isn't a beam?

 

[Rickard.]

Shouldn't the construction drawing include trusses or calculations? What will support the truss? As I said; For me, nothing in this is obvious...

The outer walls support the trusses, exactly how it is designed is usually determined by the truss manufacturer's own designers.

You can see the entire truss in the drawing, the lower chord is hidden in the insulation but it is probably just a suggestion of how it might look.

 

[ninjaman]

Yes, it might be intended like that and a bit unclearly drawn. But then the timber quality shouldn't have been specified since the truss supplier determines that. What about the floor joists then? Is there a wall where there isn't a beam?

No, no wall so I guess more beams are needed. There is no load-bearing wall on the opposite side of the HEA-beam.

 

[ninjaman]

The outer walls support the roof trusses, exactly how it is designed is usually determined by the roof truss manufacturer's own designers.

You can see the entire roof truss in the drawing, the lower arm is hidden in the insulation, but it is probably just a suggestion on how it may look.

Ok! So the outer walls support everything. But on the other hand, it feels a bit strange to have a load-bearing wall in the middle of the house and reinforce it with an HEA beam if it's just a few floor planks that constitute the load. As I said; I'm just trying to understand how things work

 

[Rickard.]

A truss is much stronger than just joists. The weight on a floor structure is not the structure itself but the furniture and people moving on it; noticeable deflection is not okay.

I'm not an expert on this, but I don't understand how the floor structure is supposed to work without more load-bearing walls/beams underneath.

 

[justusandersson]

It is an amateurishly made drawing. I completely agree with @witten. The construction won't hold, neither the roof nor the new intermediate floor. There are no vapor barriers, and the windproofing is misplaced. Dangerous in its neatness.