Why did the ceiling sink, took down interior wall

[tompaa1980]

Now, concrete tiles are not much heavier than clay tiles, as has been extensively discussed here on the forum.

Googled and you have to take it with a pinch of salt since I just picked the first listing for each. Clay tiles 2.8 kg each, concrete slab 4 kg each.

Depends a bit on the manufacturer. Benders Palema Benderit 2-wave concrete tiles weigh 38.8 kg/m2 while Vittinge classic T11 2-wave clay tiles weigh 30.8 kg/m2. On 150 square meters, it becomes 1.2 tons more weight with concrete tiles. Admittedly spread over the entire roof area, of course, but it's still quite a weight difference on paper, so to speak.

Looked at Bauhaus on two different tiles. 2.8 kg each for clay and 4 kg for concrete. That's a 1400 kg difference on 130 square meters, if I calculate correctly. 3640 kg against 5200 kg. Then it depends on what the max weight is adapted for, and if you throw in a small slope up north with a meter of snow, there could be a certain risk.

 

[Huddingebo]

So, free-spanning trusses are just a myth and don't work?

Of course, you just need to consider deflection and creep strength and dimension accordingly.

The question is whether a prefab manufacturer fully accounted for this during the wood-saving 70s when they even designed load-bearing exterior walls with 70x38 studs...
And took into account that the sketched interior walls could be removed. They may not support the floor but certainly stabilize it.

It won't collapse, of course, but you should expect some deformation.
Also, that wind gusts will make the house creak more than before.

 

[Thomas_Blekinge]

I was also in the process of tearing down an interior wall that I considered non-load-bearing. During the process, sagging occurred, and I became scared. Quick as a flash, we propped it up with an interior door. The next day, we got a support prop and ordered a glulam beam, which we then installed over the opening. Now it's calm.

 

[Henrik Lindberg]

I live in a similar Gullringshus from 1963. Here, the corresponding wall was opened about three meters, but it was supported in the attic, from the outer wall to the chimney, as the carpenter assessed it as load-bearing. (Previous owner.)

I think the carpenter made the right decision regardless of whether it is formally load-bearing or not. A neat solution too to hang it in the subframe in a cross beam in the attic, which I assume he did? There's a risk of the ceiling cracking when you have like half the span right next to a bay with the full span. In an ideal world, that wall would have had a telescopic connection at the top to accommodate about 20 mm deformation, but they didn't have that in the 60s.

 

[13th Marine]

Of course, just consider deflection and creep strength and design accordingly.

The question is whether a prefab manufacturer did that fully during the wood-saving 70s when they even constructed load-bearing exterior walls with 70x38 studs...
And considered that the drawn interior walls could be removed. They may not support the floor, but they certainly stabilize it.

It's obviously not going to collapse, but deformation should be expected.
Just like strong winds will make the house creak more than before.

So a correctly dimensioned truss can be self-supporting?

 

[Huddingebo]

So a correctly dimensioned truss can be self-supporting?

Of course.
The question is just how far they went in the dimensioning when this prefabricated house was designed over 50 years ago.

 

[GoC]

Of course.
The question is just how far they went in the design process when this prefabricated house was developed over 50 years ago.

There were well-educated engineers even back then.
No difference in calculating the same truss today. It's a 2m high truss, you just have to calculate it. You have all the measurements, and perhaps you can assume the dimensions.
The calculation method is from the 1800s but still works today.

 

[grovspacklarn]

Googled and then you have to take it with a grain of salt since I just took the first of each listing up. Roof tiles 2.8 kg each, concrete slab 4 kg each.

Checked at Bauhaus on two different tiles. 2.8 kg each for clay and 4 kg for concrete. It becomes a 1400 kg difference on 130 square meters if I'm calculating correctly. 3640 kg versus 5200. Then it depends on what the maximum weight is adapted to, and if you add a small slope up in the north with a meter of snow, there can be a certain risk.

Clay also absorbs moisture in a different way; it's not fair to compare straight across like that. But regardless, it's a fairly marginal difference. The roof should withstand 30cm of wet snow; you, who like numbers, can calculate what that weighs.

 

[13th Marine]

Of course.
The question is just how far they went with the design when this prefabricated house was produced over 50 years ago.

It is relatively easy for TS to compare the dimensions of the roof truss with the tables from träguiden that I linked in post 69.

 

[Sebyhed]

I think the carpenter made the right decision regardless of whether it is formally load-bearing or not. It's also a nice solution to hang it in the underframe on a cross beam in the attic, which I assume he did? Risk of the ceiling cracking when you have about half the span right next to a section where it’s the full span. In the best of worlds, that wall would have had a telescopic connection at the top that could absorb about 20 mm of deformation, but they didn’t have that in the '60s.

Indeed! A cross beam with support at the ends where the trusses "hang," carefully nailed with small suitable wooden pieces. Today, it would have been screwed joist hangers or similar for such a job.

 

[Huddingebo]

There were well-educated engineers even back then.
No difference in calculating the same truss today. It is a 2m high truss, you just have to calculate it. You have all the measurements and maybe you can assume the dimensions.
The calculation method is from the 1800s but still works today.

Yes, there certainly were, on average better educated than today. But bad solutions and constructions were made even back then. This is often talked about here on this excellent forum. Regardless if it was embedded wood pieces, cold concrete foundations, or poor ventilation when the first houses with electric heating came.

No one here knows how the house and roof trusses have been calculated, and rules and calculation procedures have changed.

For example, it was incredibly common for houses with plank frames and "Svensk" trusses to bulge out on the long sides due to structurally weak designs and inadequate fastening.

 

[stugfar]

@justusandersson, of blessed memory. He calculated first and then answered.

https://www.byggahus.se/forum/threads/medlemmen-justusandersson.449709/

 

[Kenneth-w]

You previously wrote that “I live in a similar house (LB) and several neighbors have removed the equivalent wall. It's not surprising that the roof comes down when the span increases. It doesn't have to mean that the wall is load-bearing.”

And now you're saying nothing at all?
According to the drawings, it strongly appears to be load-bearing as it has been included in a section drawing..
But what do I know, maybe you have enough knowledge since your neighbors have removed their walls in their houses!

The fact that walls are drawn in a section drawing doesn't necessarily mean they are load-bearing. Sections on a drawing merely show a slice through the house.

 

[AG A]

It looks rather weak.
But then answer why the trusses have been made asymmetrical if they are supposed to span freely across the entire width between the outer walls?
Just the fact that it initially sags a whole centimeter when removing an interior wall raises questions.
The roof is guaranteed to continue sagging down a few centimeters. Even if the trusses may never break.

What many confuse is sagging, instantaneous settlement. 10mm is, indeed, a relatively small sag. BUT, 10mm of instantaneous settlement is a lot. Sure, you can squeeze in studs in a non-load-bearing wall, thereby giving the impression of being load-bearing. But try hammering in studs that are 10mm too long. You can't do it.
As I've mentioned before, it's summer now. Likely there wouldn't have been a sag of 10mm in winter if it hadn't been supported.

 

[smuttebo]

Yet another question about load-bearing walls, I'm in the process of tearing down the wall between the kitchen and living room. I and several others assessed the wall as non-load-bearing. The house is a Gullringshus from 1966. The wall runs along the roof ridge. The distance between the exterior walls is 7.4m. The only walls I can find marked as load-bearing in the plans are the basement walls.

I have truss roof beams and the studs in the wall seemed very weak by my assessment, 50x35mm. The distance between the studs was over 100 cm in one place, none of the studs were centered with the floor joist. The wall was between 2 door openings and ends with an opening of 4 m.

During demolition, there had been pressure on the last stud closest to the exterior wall, but when sawing it, the stud broke easily and the ceiling dropped about 10 mm... the ceiling is now propped up to the height before demolition. So my thought is, did the wall have a load-bearing function or is it normal for the ceiling to sink slightly over time?

Half a meter of wet snow on the roof usually reveals any weaknesses.