Hello
We are planning to build a dormer on our house and a small wild idea has come up, which we thought we would ask if anyone could say whether it is possible/reasonable to build in this way regarding, for example, structural integrity.
The longest span is 3.6m and the other is 2.4m. The ridge height is about 2.3m and at the supporting beams about 1.15m.
The roof angles are 27 and 14 degrees. Today, there is no beam/balanced structure at the ridge, but with the current interior option, it is possible to have support along the entire truss at each edge of the dormer and support along half of the truss in the middle of the dormer, on the side where the dormer is. Directly under the ridge, there is a heart wall on the lower level that supports the joist.
Then I would also gladly receive comments on how you think a dormer of this kind would look.
Best regards
M
We are planning to build a dormer on our house and a small wild idea has come up, which we thought we would ask if anyone could say whether it is possible/reasonable to build in this way regarding, for example, structural integrity.
The longest span is 3.6m and the other is 2.4m. The ridge height is about 2.3m and at the supporting beams about 1.15m.
The roof angles are 27 and 14 degrees. Today, there is no beam/balanced structure at the ridge, but with the current interior option, it is possible to have support along the entire truss at each edge of the dormer and support along half of the truss in the middle of the dormer, on the side where the dormer is. Directly under the ridge, there is a heart wall on the lower level that supports the joist.
Then I would also gladly receive comments on how you think a dormer of this kind would look.
Best regards
M
The main reason is that the ventilation unit and all ventilation ducting are located there. Sure, the units can be moved, but we still need space for the ducting since all supply and exhaust air is on that side of the house.
Then the building height becomes too high as our zoning plan does not allow for a greater building height. If I measure 45 degrees down from the highest point of the dormer to the outer wall, it just manages as it is now. Then there's tile on the roof, so I cannot/should not reduce the roof pitch to less than 14 degrees.
/m
Then the building height becomes too high as our zoning plan does not allow for a greater building height. If I measure 45 degrees down from the highest point of the dormer to the outer wall, it just manages as it is now. Then there's tile on the roof, so I cannot/should not reduce the roof pitch to less than 14 degrees.
/m
The main issue is probably the trusses where you cut the top chord. These trusses lose their entire normal function, and it must be replaced with something else. As you mentioned, a ridge beam. Then all the load that lands on the ridge beam needs to go somewhere, either through columns down through the entire house, and then the foundation must also handle the load. The calculation chain is not complete until you reach the ground under the house. 
Another option is to significantly reinforce the remaining trusses. But then the load increases where these stand on the wall plates, so you need to watch out there too, and in the same way as before, all the way down to the ground.
Another option is to significantly reinforce the remaining trusses. But then the load increases where these stand on the wall plates, so you need to watch out there too, and in the same way as before, all the way down to the ground.
Yes, that's what I'm getting at. What I'm trying to figure out is whether it's worth getting someone to calculate this or if it's doomed to fail from the start.
I used Moelven's beam calculation program, and it seemed like the vertical load on each pillar would end up being around 10-15 KN. I calculated in pairs, one beam for the 2.4 transition and one for the 3.6 transition. The three pillars would end up on the floor directly above a standing 45*95 in the load-bearing wall on the lower floor (luckily there is a support in the load-bearing wall under each beam in the floor structure) and that support stands on a 37*90 resting on the concrete slab. Unfortunately, I don't have access to the slab's drawings at the moment, but there is some form of reinforcement under the load-bearing wall, though I can't remember what it looked like.
Perhaps I need to dig out some of the well-hidden load calculation examples from technical school 25 years ago.
I used Moelven's beam calculation program, and it seemed like the vertical load on each pillar would end up being around 10-15 KN. I calculated in pairs, one beam for the 2.4 transition and one for the 3.6 transition. The three pillars would end up on the floor directly above a standing 45*95 in the load-bearing wall on the lower floor (luckily there is a support in the load-bearing wall under each beam in the floor structure) and that support stands on a 37*90 resting on the concrete slab. Unfortunately, I don't have access to the slab's drawings at the moment, but there is some form of reinforcement under the load-bearing wall, though I can't remember what it looked like.
Perhaps I need to dig out some of the well-hidden load calculation examples from technical school 25 years ago.
That doesn't sound like a particularly large pillar load. It should be possible to transfer it through the center wall and then to the slab without too much trouble. That's what I think ...mape17 said: