I have installed a KKS beam 70x70x4 over an opening of 2 m in a wall over a turf roof, with two rafters resting on the wall, while the middle one, one meter out, rests on the beam. When removing the supports, nothing moved, but if precipitation occurs, do I need to double the beam horizontally, as the standing height does not allow for vertical doubling.
Regards, Bengt Andersson
Regards, Bengt Andersson
Hello Bengt and welcome to the Byggahus forum!
Don't you mean a KKR beam? If so, you can load a 2-meter-wide KKR beam, 70x70x4, with a point load in the middle of about 600 kg and get a deflection of 6 mm, which corresponds to 1/300 of the span. If you use a 140x70x5 laying down instead, you can double the load to 1200 kg with the same deflection. Whether that is sufficient for your needs, I can't calculate without knowing more about the roof's design, dimensions, and snow load conditions.
Don't you mean a KKR beam? If so, you can load a 2-meter-wide KKR beam, 70x70x4, with a point load in the middle of about 600 kg and get a deflection of 6 mm, which corresponds to 1/300 of the span. If you use a 140x70x5 laying down instead, you can double the load to 1200 kg with the same deflection. Whether that is sufficient for your needs, I can't calculate without knowing more about the roof's design, dimensions, and snow load conditions.
Yes, it is a KKR-beam, the roof consists of corrugated sheet, tar paper, platon mat, and one to two layers of sod, the weight of the sod varies depending on precipitation, it hasn't rained in over a month, I've never seen snow lie on this roof, in nearly forty years (it is located a hundred meters from the sea, on the eastern Öland) the snow blows away.
Appreciate your response:
Bengt Andersson
Kårehamn
Appreciate your response:
Bengt Andersson
Kårehamn
An old turf roof can weigh as much as 250 kg/sqm. Geometry is very significant. If the house is 5 m wide and the rafters only rest on the outer walls, the point load on the steel beam can reach 1200 kg. If there is a central supporting wall that the rafters rest on, the point load is only half as large. The value of the snow load depends greatly on the roof shape. However, one should not neglect the problem of snow loads, they are calculated over a very long term.
There is still an opportunity to place a similar beam parallel to the one I laid, before I seal the wall ends. For safety.
The walls are 75 cm thick and have an outer dimension of 4 m, but the wall plates were on the inner edge of the walls, so they were only 2.5 m between.
The steel beams are placed right at the outer edge of the wall plate.
It is about creating a portal in part of a large basement, so I plan to demolish the wall on the other side as well, so I might lay the beam intended there as extra reinforcement where I am now and get another beam when I reach that point.
Ceiling height is limited, so I prefer the beams not to be too tall.
Bengt Andersson
Kårehamn
The walls are 75 cm thick and have an outer dimension of 4 m, but the wall plates were on the inner edge of the walls, so they were only 2.5 m between.
The steel beams are placed right at the outer edge of the wall plate.
It is about creating a portal in part of a large basement, so I plan to demolish the wall on the other side as well, so I might lay the beam intended there as extra reinforcement where I am now and get another beam when I reach that point.
Ceiling height is limited, so I prefer the beams not to be too tall.
Bengt Andersson
Kårehamn
Do it! Add an identical beam.
Hi Justus, Thank you for your advice.
The extra beam allows me to sleep, even if it rains.
Regards, Bengt
The extra beam allows me to sleep, even if it rains.
Regards, Bengt
Surely a drawing means more than 1000 words and is absolutely necessary for a proper calculation. Since I didn't have a drawing, I chose to work backwards and calculate what a beam of the current size can handle in terms of load. Thus, the responsibility ended up on TS.