Hi, we are renovating our cottage and I want to take the opportunity to review a support beam that was installed sometime in the 60s when the cottage was expanded.
The opening is currently about 2.5 meters and on one side it connects to the chimney and on the other side to a wall, with an outer roof, a shed roof with a 4-degree angle above. It has been supported with two nailed-together 170-mm beams so far, but I want to replace it with a steel beam, which I will recess into the ceiling. I also want to bypass the chimney, which will be taken down, and instead make a support in the existing wall beyond the chimney and in the existing wall on the other side, the new length between supports will be about 4m.
In laminated timber, a 90*315mm beam would do the job, but if I want a steel beam instead, what should I use? I got help with an estimate of the beam and ended up with an HEA 160, which I can accept, but what does the wisdom on the forum say? The laminated timber beam would have had a utilization rate of 65% with a 13 mm deformation.
If I can manage with an HEA 160, then I can avoid having a visible beam under the ceiling, which would be fantastic, but it's more important that the roof holds than that I don't have to box in a beam—at the same time, two 170mm beams have done the job for 50 years.
The opening is currently about 2.5 meters and on one side it connects to the chimney and on the other side to a wall, with an outer roof, a shed roof with a 4-degree angle above. It has been supported with two nailed-together 170-mm beams so far, but I want to replace it with a steel beam, which I will recess into the ceiling. I also want to bypass the chimney, which will be taken down, and instead make a support in the existing wall beyond the chimney and in the existing wall on the other side, the new length between supports will be about 4m.
In laminated timber, a 90*315mm beam would do the job, but if I want a steel beam instead, what should I use? I got help with an estimate of the beam and ended up with an HEA 160, which I can accept, but what does the wisdom on the forum say? The laminated timber beam would have had a utilization rate of 65% with a 13 mm deformation.
If I can manage with an HEA 160, then I can avoid having a visible beam under the ceiling, which would be fantastic, but it's more important that the roof holds than that I don't have to box in a beam—at the same time, two 170mm beams have done the job for 50 years.
A 4-meter-long glulam beam at 90x315 has a deflection of about 13 mm under an assumed load of 12 kN/m. Under the same conditions, the deflection of an HEA 160 is 11 mm, so an HEA 160 can replace the intended glulam beam under these conditions.
If you instead use a 165x270 glulam beam, the deflection is 11 mm. An HEA beam should ideally be fire protected, which adds a small increase in height. The HEA beam will be more expensive, expect around 3000 SEK.
I chose the load of 12 kN/m to achieve a deflection of 13 mm on the first glulam beam. It feels a bit much for a summer cottage in Skåne. How did you calculate the load on the beam? 13 mm corresponds to 4 meters divided by 300, which is reasonable.
If you instead use a 165x270 glulam beam, the deflection is 11 mm. An HEA beam should ideally be fire protected, which adds a small increase in height. The HEA beam will be more expensive, expect around 3000 SEK.
I chose the load of 12 kN/m to achieve a deflection of 13 mm on the first glulam beam. It feels a bit much for a summer cottage in Skåne. How did you calculate the load on the beam? 13 mm corresponds to 4 meters divided by 300, which is reasonable.
Thank you for the help! I obtained the information by inputting my measurements into one of the free sizing programs online. I could actually calculate for one size smaller, but then I was right on the edge, 95% utilization rate.
Does one need to clad the beam separately, not just integrate it into the ceiling?
Does one need to clad the beam separately, not just integrate it into the ceiling?
I'm not a super expert on this. Fire regulations have changed a lot over the years. I'm better at fire safety on a more general level. Regardless of what the standards say, I think you should consider your own safety. If you clad the underside of the ceiling with plasterboard and insulate around the beam with mineral wool, it should be enough.Scouten said:
That sounds reasonable, so I'll do it.