Roof trusses

[Ingenjören]

Those of you using older building descriptions for roof trusses should be aware that Boverket changed the applicable snow loads in April this year!!!
See more at:
http://webtjanst.boverket.se/Boverket/RattsinfoWeb/vault/BKR/PDF/BFS2006-11BKR10.pdf

Here in my municipality, the load has increased from 1.5kN/m[sup]2[/sup] to 2.0 kN/m[sup]2[/sup].

/The Engineer

 

[Ubbe]

Those using older construction descriptions for trusses should be aware that Boverket changed the snow loads regulation in April this year!!!
See more at:
[link]

Here in my municipality, the load has increased from 1.5kN/m[sup]2[/sup] to 2.0 kN/m[sup]2[/sup].

/Ingenjören

Of course, one can keep this in mind, but the question is whether it makes any big difference in practice?
It's not exactly as if the houses built according to the old standard immediately need reinforcement to avoid collapsing :
Why wouldn't what held 5 years ago hold today?

When you look at a truss in an old building and compare it to a modern truss, you become a bit curious about how old houses have managed to survive for 100 years with such flimsy trusses

 

[MartinT]

If you look at a truss in an old building and compare them with a modern truss, you become a bit puzzled about how old houses have survived for 100 years with such flimsy trusses

I don't have an exact answer to that, but I can imagine that back in the day, they used better timber for the trusses, meaning only heartwood. Possibly, the roof's own weight was also lighter, with less insulation, lighter roofing material, etc.

Was at Skokloster Castle in Håbo municipality (south of Uppsala) over the weekend, which is a castle that began construction around 1650. The interesting thing there is that there is a room, or rather a banquet hall, which hasn't been completed, and you can see in detail how the trusses are constructed. Very interesting.

 

[ordain]

If you look at a truss in an old building and compare them with a modern truss, you become a bit puzzled over how old houses could survive for 100 years with such flimsy trusses

The answer is that not all houses made it, and from time to time roofs collapsed when there was too much snow (it still happens occasionally, but it's rare). That's something we modern people want to avoid.

 

[Ingenjören]

The Swedish National Board of Housing, Building and Planning's construction regulations are not retroactive, meaning older houses do not need to be rebuilt when regulations change. What I meant is that they are mandatory rules for new construction and major renovations. If you don't consider the new snow loads, you are committing a legal offense.

One of the reasons why the standards for snow loads have increased is actually because last winter there were several (3?) building collapses in Sweden due to heavy snow loads, including Boda school in Småland.

http://sydsvenskan.se/sverige/article145800.ece

/The Engineer

 

[Mats]

In the past, people were also sensible and shoveled the roofs when there was a lot of snow on them.

However, the roofs were at least as heavy as they are today. Almost only tile or slate back then and very light sheet metal roofs with massonit underneath today.

 

[Ubbe]

In the past, people were also sensible and shoveled the roofs when there was a lot of snow on them.

Exactly what I was going to write ;D

Just for fun, I will check the dimensions of the houses at home and see what they should have been according to today's standards. A wild guess says that the timber dimensions are 25-50mm below what they should be today.. The residential house was built in 1910