Load-bearing or non-load-bearing, two structural engineers say different

[StrukturalAB]

What do you mean by "yttre takstolen"?

 

[SvanteC]

Threads like this make me miss @justusandersson

 

[Workingclasshero]

What do you mean by "outer truss"?

The wall to be removed adjoins the outer wall, so the truss located on the gable, the outer one. As well as the "inner" one too, of course, but that load can probably be distributed across several trusses or go straight down to the basement wall, but then the wall in the room might need a beam.
/W

 

[JoLi81]

We have a house from '53, with a regular gable roof, but also with free-spanning trusses. When we were going to tear out the old kitchen and open up the "upper floor" (split-level house, where the upper floor has the kitchen, etc., and concrete intermediate floor with a load-bearing wall in the lower level), we also contacted a structural engineer. Although we had drawings of the trusses and quite a good foundation, he recommended a glulam beam that would be "suspended" within the trusses. This was because the approximately 60+ years since the house was built could have caused settling, some material fatigue, and other factors that could cause sagging in the ceiling. We installed a new (lowered) interior ceiling with panels that are plastered, instead of the previously stretched paper. In the 10+ years that have passed, we haven't had the slightest crack in the ceiling, which should mean that everything is stable and secure.

That said, even if it might be sufficient as it is, it could be a good idea to reinforce according to a structural engineer's recommendations, simply to ensure it lasts another 60 years without problems.

 

[Vrana]

Hello
You have at least 2 paths to take.
One path is a glulam beam or steel beam in the room.
The other path is to reinforce the truss when you are already replacing the insulation.
There are advantages to the latter as it avoids visible posts and beams, and it becomes much cheaper and easier to address.
Relying on the old potentially unfavorably aged trusses without inspection may earn you the not-so-honorable "Darwin Award",
/Workingclasshero

Help a beginner in the context. How do you reinforce a truss?

 

[Workingclasshero]

Help a beginner in the context. How do you reinforce a truss?

There are many ways. I see no problem with you improvising once you've extracted all the loose fill and taken pictures of the current situation. Then there is someone in the thread who is significantly more knowledgeable about truss constructions and can answer more professionally. /W

 

[bergqvizt]

Check out https://www.svenskttra.se/ for free-spanning or truss roof truss and check in the attic how yours is constructed.

 

[StrukturalAB]

Help a beginner in the context. How do you reinforce a truss?

By screwing and gluing additional battens or construction plywood onto the part that needs reinforcement. But there are many different methods, though more timber is usually the simplest.

 

[StrukturalAB]

The wall that needs to be removed borders on the outer wall, so it's the rafters on the gable, the outer one. Also the "inner" one of course, but that load can probably be distributed over several rafters or go straight down to the basement wall, but then maybe the wall in the room needs a beam.
/W

Aha. The simple way to reason is that the load from snow and the dead weight of the roof is evenly distributed on inner rafters. So if they are placed 1.2 m apart, they get a strip of load that is 1.2 m wide. 0.6 m from each side. The gable one, therefore, gets a 0.6 m load width. With that reasoning, reinforcing a gable rafter does not increase the capacity of the inner ones.

But, if you take it a step further, you take into account the stiffness of each rafter and the roof decking. And then it is the case that the rafter that is the stiffest (strongest) gets the most load. Then the first reasoning no longer applies.

In the current case, an infinitely strong gable rafter would still not help much as the roof decking is weak.

The above is a simplified reasoning of the effect of supports with different stiffness. Something you usually don't consider in house construction. I have a background as a bridge designer, where it is more precise.

 

[Workingclasshero]

Aha. The simple way to reason is that the load from snow and the roof's own weight is evenly distributed on inner trusses. If they are spaced at s1.2m, they get a strip of load that is 1.2 m wide. 0.6 m from each side. The one on the gable consequently gets a load width of 0.6 m. So with that reasoning, a reinforced gable truss does not increase the capacity of the inner ones.

But, if you take it a step further, you consider the stiffness of each truss and the sheathing. And then it is such that the truss that is the stiffest (strongest) gets the most load. Then the first reasoning no longer applies.

In this particular case, an infinitely strong gable truss wouldn't help much since the sheathing is weak.

The above is a simplified reasoning of the effect of supports with different stiffnesses. It is something usually not considered in house construction. I have a background as a bridge designer, where it matters more.

I understand your way of thinking, your reasoning feels correct, as it was roughly what I was thinking, but failed to convey in text. Of course, a stronger truss is not enough on its own, but you can use it to distribute the force to the other trusses, this written in the hope that "someone" clarifies if necessary.
/W

 

[Aajnor]

Can't find any drawings of the rafters. However, it is quite a low-sloping roof with a 6-degree angle. It's hard to see anything at all in the small attic plus it's full of wood shavings. However, we will vacuum it out in the spring and install cellulose insulation, so maybe we can see more then.

Take a photo of the rafters and post it here.

 

[peteds01]

I thought the same thing spontaneously and started tearing down happily but became uncertain with such mixed opinions. Everything else in the house is so damn solidly built that I'm still inclined to trust those roof trusses.

If you're going to tear down the interior wall at the red cross for an opening between the living room and kitchen, you can brace up a beam type 2//45x120 in the new opening with 45x90 on the sides.

 

[Vrana]

Take a photo of the rafters and post it here

What can be photographed under the kutterspån I'll definitely photograph, but right now there's a 3 m deep ditch under the hatch, so no ladder we own reaches up (drainage). In a week it will be filled again, then I'll go up there!

 

[Kane]

If you are going to tear down the interior wall at the red cross for opening living room - kitchen, you can prop up a beam like 2//45x120 in the new opening with 45x90 on the sides.

Have you calculated that?

 

[kjellolov51]

Hi! We have a long narrow single-story house with a brick basement. Between the floors, there is a concrete slab. According to the original drawings from '67, only the outer walls are load-bearing, but there are 8 m between them. Low-sloped roof. Through the ground floor, there is a wall running along the entire length of the house according to the drawing.

We asked a building engineer + constructor if it was possible to demolish the wall between the kitchen and the living room, and they said it wasn't load-bearing. The neighbor happens to have an identical twin house and has had similar thoughts; the engineer they hired says it is definitely load-bearing and even advises against a glulam beam, insisting on a steel beam.

How can it differ so diametrically? Anyone with similar experiences?

There shouldn't be any problem opening up the wall, but I would leave 500 mm against the outer wall.