Hello.
Ordering a sunroom from Willab. I have received approval from the city planning office for a building notification to construct an "attefallsuterum" that measures 4130x3318 mm, and if I place an additional post about 600 mm from one edge, I can use a 56x225 glulam beam as the front beam according to Willab's calculations (snow zone 1.5). The only problem is that I can only build about 2410 mm in height at the back because my housing association doesn't want the structure to protrude on the wooden facade (there's a concrete facade below). Foolishly, I missed this in the association's rules when I built my new deck last summer. To make it work, I need to reduce the front beam to 180 to still have a 4-degree roof pitch on the sunroom. I used the formula (b/h^3)/12 that a kind member mentioned before to find a lower beam, and a 115x180 glulam beam would work. However, it's a bit more work since the posts are 115x115, so I'd need to widen them at the front to create a mounting surface for the side beams on the posts. As an alternative, I've considered using a bx200 mm veneer beam as the front beam instead to reduce the beam's width. However, I haven't found any conversion program, and my knowledge of strength of materials is a bit rusty. Does anyone here know which width I need?
Ordering a sunroom from Willab. I have received approval from the city planning office for a building notification to construct an "attefallsuterum" that measures 4130x3318 mm, and if I place an additional post about 600 mm from one edge, I can use a 56x225 glulam beam as the front beam according to Willab's calculations (snow zone 1.5). The only problem is that I can only build about 2410 mm in height at the back because my housing association doesn't want the structure to protrude on the wooden facade (there's a concrete facade below). Foolishly, I missed this in the association's rules when I built my new deck last summer. To make it work, I need to reduce the front beam to 180 to still have a 4-degree roof pitch on the sunroom. I used the formula (b/h^3)/12 that a kind member mentioned before to find a lower beam, and a 115x180 glulam beam would work. However, it's a bit more work since the posts are 115x115, so I'd need to widen them at the front to create a mounting surface for the side beams on the posts. As an alternative, I've considered using a bx200 mm veneer beam as the front beam instead to reduce the beam's width. However, I haven't found any conversion program, and my knowledge of strength of materials is a bit rusty. Does anyone here know which width I need?
It's entirely correct that you can replace 56x225 with 115x180. 180 mm is normally the lowest height for glulam beams. You can slightly reduce the height by splitting a 165x315 beam (it should have the additional designation "h" which indicates that it is homogeneous). This way, you can go down to 155 mm in height. However, the height gain comes at a high cost. The posts should be chosen to match the width of the beam. It's better to place a smaller post at an angle to provide support for the side beam. I don't think a veneer beam is an option in this case (otherwise an excellent material).
Hi,J justusandersson said:
Thank you so much for the help
. I have also tried to dust off my knowledge of strength of materials from school and used the program Finnwood 2.3.1 from Metsäwood and it also suggested a 115x180 beam. A 90x180 would have worked too if only I knew how to make it stiffer since the bending moment is too large. One possibility is to add a fourth post to reduce the span at the expense of a shorter front section of the conservatory. Going up further in dimension in width to a split 165 was an interesting thought, but that will be a last resort as I think the beam will look very overdimensioned in relation to the rest of the construction (it starts to hurt already at 115).Regarding support for the side beams, I am considering gluing and screwing a 36x115 mm joist to the front posts, or alternatively attaching them with beam hangers or angle brackets to the front beam. They don't seem to have a load-bearing function, merely aesthetic. I compared with Skånska byggvaror's "Fira" lean-to frame, and it doesn't have side beams, only a top joist to attach the frame to the conservatory section.
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So now the conservatory is finally ordered and delivery is approaching. As I mentioned earlier, I need to replace the front beam with either 90x180 or 115x180 to lower the height at the back. I think 90x180 glulam should be enough, but I'm leaning towards 115x180 (most like 56x225 in properties) which I will notch at the outer edges about 50 mm to make room for the side beams (56x180 glulam). This should work since the greatest load will be on the inner columns (see attached image). What do you think?
I also need to change the side beams to 56x180 (delivered will be 56x225) to adjust the height to the new beam. So my question is whether I should order new 56x180 beams (seems to be available only at Skånska byggvaror) for the sides, or if I can cut the delivered 56x225 beams along the length. I know these are not made of homogeneous glulam, but on the other hand, the side beams don’t support any load as I see it but are only for the attachment point for the conservatory sections' tracks.
I also need to change the side beams to 56x180 (delivered will be 56x225) to adjust the height to the new beam. So my question is whether I should order new 56x180 beams (seems to be available only at Skånska byggvaror) for the sides, or if I can cut the delivered 56x225 beams along the length. I know these are not made of homogeneous glulam, but on the other hand, the side beams don’t support any load as I see it but are only for the attachment point for the conservatory sections' tracks.
The possibility of notching out a beam at the support is limited, among other things, by the need to have enough material left to withstand the shear forces that occur there. With 115x180, this should not be a problem in this case. If you split a non-homogeneous glulam beam, you can expect reduced stiffness (modulus of elasticity) but it is certainly sufficient considering the span and load.
Thanks for the feedback . I checked with the dimensioning program on byggbeskrivningar.se before asking my question here on the forum, and according to those calculations, 10 mm support for the front beam for the outer posts should suffice. However, I was a bit unsure since that program limited the center-to-center measurement between the outer and inner posts to 600 mm, but my framework has 445 mm. As for the side beams, maybe it's easiest to order 2 pieces of 56x180 from Skånska byggvaror or order an additional 115x180 and have it split in two parts.
. I checked with the dimensioning program on byggbeskrivningar.se before asking my question here on the forum, and according to those calculations, 10 mm support for the front beam for the outer posts should suffice. However, I was a bit unsure since that program limited the center-to-center measurement between the outer and inner posts to 600 mm, but my framework has 445 mm. As for the side beams, maybe it's easiest to order 2 pieces of 56x180 from Skånska byggvaror or order an additional 115x180 and have it split in two parts.