A bit of background, the log house we bought has an older extension built in '83 with homemade trusses and 45x95 exterior walls, 45x45 interior walls on a concrete slab with a raised floor. We're not entirely fond of the way it's built, so we're considering simply demolishing it and starting over. We're going to redesign the floor plan anyway, and we want it to be open to the ridge and not have an offset ridge.
The picture below shows how the previous owners did the expansion.
I need a bit of help getting feedback on my structural drawing and possibly if I've considered the correct dimensioning of glulam beams + pillars. I've used the Building Descriptions dimensioning program.
The old log house is 6x9m externally. The extension is 3.4m long and 7.4m deep (wide?).
The idea is to match the ridge with the log house and we plan to lay clay tiles on the entire house. The protruding section with a lower pitch will have sheet metal covered.
The roof pitch is 30 degrees. The protruding section has a pitch of about 10 degrees. The building height I've drawn is 2500mm.
Snow zone 2.0 Västerås.
The ridge beam can also have a pillar in the middle if needed, as there will still be a wall there.
See the sketches below, the "log house" isn’t entirely accurately drawn but it's to show how the extension will look. The first picture is a drawing of the roof section and the frame.
Also, how should the new frame be attached to the old log frame?
Hey Fredrik, is this an old acquaintance? How wide is the extension minus the protruding part?
Hey Justus,
Yes indeed, you commented on this in a previous thread I made, whether it was just after we bought it or before, I can't remember... So you probably recognize the picture. However, I don't think I've previously posted anything about the dimensions unless I've become senile (28 years old so maybe it's starting??)
It's 6.2m wide. I measured it on the outside of the facade.
edit: of course minus the protruding part, which is approximately 1.35m. So about 7.5m in total.
Yes, you have quite substantial margins on the glulam. It is not too weak. You can easily decrease the beam dimensions by a notch. 90x315 for the ridge beam and 90x270 for the side beam. What utilization rate did you get when using the Byggbeskrivningars program?
I noticed that I entered some wrong measurements. I got 66x315 now but with too high deformation (13mm). 90x315 gives a utilization rate of 65%, so that's good.
However, I should increase the size of the roof beams to 42x270, which results in a deformation of 10mm (66% utilization rate). Alternatively 56x270.
Construction description programs say that a side beam of 90x270 gives a deformation of 15mm (L/229) (86% utilization rate), and I calculated this as an "opening in the wall of a one-story house" so it might not be entirely accurate. But I figured it can't be too weak...
Attached are the calculations I made. It gets a bit tricky because the program assumes a self-weight for the interior ceiling, which I understand. But now we aren't going to have double gypsum in the ceiling. If I change from 0.6kn/m2 to 0.25kn/m2, I get a slightly lower utilization of the load-bearing beam, but the column load remains essentially unchanged.
The deflection data is accurate in the Construction Descriptions app with the loads they specify, but I don't understand how they arrive at these with the given assumptions about snow and dead weight. But you don't need to worry, they are conservative.
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