I am planning to extend the house by adding 4 roof trusses, i.e., about 5m, including basement and upper floor. The house is about 7m wide.
5m makes it quite straightforward to put together a floor joist between the basement and the ground floor; regular 45x220 with 600 centers and screw-glued floor chipboard should suffice.
The problem is that normal trussed rafters with that width require a supporting central wall near the middle, and that wall is, in turn, supported by the floor joists against the basement. I don't want a wall in the basement under the central wall of the ground floor.
I could place a glulam beam in the floor joist under the central wall, but the limitation would still be the height of the floor joist, which would likely be 220.
Perhaps one could also place a standing beam at the bottom of the central wall like a standing wall plate to distribute the pressure better.
But how do you calculate this?
5m makes it quite straightforward to put together a floor joist between the basement and the ground floor; regular 45x220 with 600 centers and screw-glued floor chipboard should suffice.
The problem is that normal trussed rafters with that width require a supporting central wall near the middle, and that wall is, in turn, supported by the floor joists against the basement. I don't want a wall in the basement under the central wall of the ground floor.
I could place a glulam beam in the floor joist under the central wall, but the limitation would still be the height of the floor joist, which would likely be 220.
Perhaps one could also place a standing beam at the bottom of the central wall like a standing wall plate to distribute the pressure better.
But how do you calculate this?
I understand now that the simplest way is to use an iron beam under the core wall.
Can someone explain a bit about different types of iron beams and what might be suitable for my application? A 5m span isn't much, so I guess it's enough to estimate the required dimensions. How about an H-beam, 120x120 with 8mm thickness?
Can someone explain a bit about different types of iron beams and what might be suitable for my application? A 5m span isn't much, so I guess it's enough to estimate the required dimensions. How about an H-beam, 120x120 with 8mm thickness?
There is surely someone here who can provide a better answer.
But, I believe it is entirely possible to make trussed rafters that span over 7m. Because that would be the span of the truss if I read correctly above? Check with a truss factory, they will also provide you with the construction calculation.
If you are going to have a supporting beam of 5m, then you need to have a constructor calculate it, as each house has its own conditions. It’s not just about the beam itself but also the support points. In our extension, we have used a couple of steel beams in the intermediate floor with a 5m span. They are 160mm high.
In many cases, you have to extend pillars all the way down to the foundation wall, and in some cases, even pour a new foundation under the cellar floor for the pillar's support.
But, I believe it is entirely possible to make trussed rafters that span over 7m. Because that would be the span of the truss if I read correctly above? Check with a truss factory, they will also provide you with the construction calculation.
If you are going to have a supporting beam of 5m, then you need to have a constructor calculate it, as each house has its own conditions. It’s not just about the beam itself but also the support points. In our extension, we have used a couple of steel beams in the intermediate floor with a 5m span. They are 160mm high.
In many cases, you have to extend pillars all the way down to the foundation wall, and in some cases, even pour a new foundation under the cellar floor for the pillar's support.
The setup should not be a problem! I have masonry walls from the basement to lay the beam on.
hempularen, what do your steel beams support? The same thing as mine, load-bearing walls? 160mm height seems to be a common dimension and maybe that's what I would need to be on the safe side...
I have the impression that it would be cheaper to lay a steel beam under the ridge beam than to buy 7m self-supporting trusses.
hempularen, what do your steel beams support? The same thing as mine, load-bearing walls? 160mm height seems to be a common dimension and maybe that's what I would need to be on the safe side...
I have the impression that it would be cheaper to lay a steel beam under the ridge beam than to buy 7m self-supporting trusses.
No, in our case they support an intermediate joist. That part of the house is an extension from the 70s measuring 5x8m (the rest of the house is from the 30s). We built an additional floor on the extension. For various reasons, the beams had to run in the 8m direction, and there was no central wall that could support (there is one, but it stands about 1m next to a steel beam in the basement).
We also have a staircase that comes up roughly in the middle of everything. So, therefore, there are two beams, one on each side of the staircase. The wooden beams (220mm) are then inserted into the beam so the joist is a total of 220mm despite the beams crossing.
An intermediate joist is often a greater load than a roof despite snow load, so it's very possible that a slimmer beam would be enough for you. But that needs to be calculated. An intermediate joist is regularly designed for 200kg per square meter (plus its own weight). This is in residential areas, in public spaces I believe the load is double that.
Our old roof on this part was trusses with a span of 8m. They did rest on the false central wall, but since it was positioned where it was, the lightweight concrete joist towards the basement would have cracked if there had been a high load on the central wall. So I believe those trusses were designed for an 8m free span.
We also have a staircase that comes up roughly in the middle of everything. So, therefore, there are two beams, one on each side of the staircase. The wooden beams (220mm) are then inserted into the beam so the joist is a total of 220mm despite the beams crossing.
An intermediate joist is often a greater load than a roof despite snow load, so it's very possible that a slimmer beam would be enough for you. But that needs to be calculated. An intermediate joist is regularly designed for 200kg per square meter (plus its own weight). This is in residential areas, in public spaces I believe the load is double that.
Our old roof on this part was trusses with a span of 8m. They did rest on the false central wall, but since it was positioned where it was, the lightweight concrete joist towards the basement would have cracked if there had been a high load on the central wall. So I believe those trusses were designed for an 8m free span.