Hello!
We have plans to renovate the roof of an extension to our 1 1/2 story house, which currently is only one story with a flat roof. We plan to add another story at an angle to the existing roof but are wondering if the wooden frame is strong enough to support an additional story.
It appears to be 2x4" lumber in the walls resting on the basement walls. The roof will be a mansard with tile/concrete tile.
We have plans to renovate the roof of an extension to our 1 1/2 story house, which currently is only one story with a flat roof. We plan to add another story at an angle to the existing roof but are wondering if the wooden frame is strong enough to support an additional story.
It appears to be 2x4" lumber in the walls resting on the basement walls. The roof will be a mansard with tile/concrete tile.
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Span?
snow zone?
snow zone?
Huddinge-Stuvsta and the distance between the wall plates is about 5.5 meters, but it shouldn't be a problem to place a beam in the middle either.
A bit on instinct (no guarantees whatsoever, in other words) I think your 2"-4" in existing walls will handle the weight from this 5.5m wide roof and snow zone.
But if you plan to use the floor on the upper level and want it "bounce-free," you will probably need something supportive on the lower level, a load-bearing wall or a glulam/steel beam. Then you'll have some challenges with load-bearing at a point inside the house, inside the inward-going exterior wall corner. There are several ways to resolve this, such as glulam beams at the ridge or trusses extending inside the house, so to speak, but whatever is chosen needs support.
These forces also need to be managed in the foundation/basement. It may involve 5-10 tonnes of point loads (possibly more), so a basement floor structure is unlikely to withstand it without additional reinforcements.
I can't really provide any clear advice or guidelines, as I know too little about this. I just wanted to point out some difficulties you should consider. An experienced designer can probably help. They've likely done this sort of thing before and have a "patent solution" ready.
But if you plan to use the floor on the upper level and want it "bounce-free," you will probably need something supportive on the lower level, a load-bearing wall or a glulam/steel beam. Then you'll have some challenges with load-bearing at a point inside the house, inside the inward-going exterior wall corner. There are several ways to resolve this, such as glulam beams at the ridge or trusses extending inside the house, so to speak, but whatever is chosen needs support.
These forces also need to be managed in the foundation/basement. It may involve 5-10 tonnes of point loads (possibly more), so a basement floor structure is unlikely to withstand it without additional reinforcements.
I can't really provide any clear advice or guidelines, as I know too little about this. I just wanted to point out some difficulties you should consider. An experienced designer can probably help. They've likely done this sort of thing before and have a "patent solution" ready.
I still think that the existing exterior walls don't cause the most trouble. In the worst case, it's just a matter of quickly opening up the walls and adding stronger studs, and getting much better insulation in the process. 
Perhaps best to contact a structural engineer before we proceed. Option 2 that we have is to just redo the flat roof with as much pitch as possible (don't want to raise it higher than the existing roof) since we have to do something about the 25-year-old roof anyway.
We can hope that someone else wants to comment here in the thread, for instance, maybe someone who has done something similar.
Maybe I exaggerated, in my ignorance. I was just thinking about a solution. To place a reinforced truss (double truss?) for the extension along the outer wall of the main building's body. Then handle the forces in the outer walls down towards the foundation beam with the help of a glulam post or extra studs. Then a glulam between the ridge on this reinforced truss and the existing truss in the house. But then the existing truss probably needs to be reinforced a bit and likely something must also be reinforced to handle the downward forces from the existing truss, as the forces increase.
Maybe I exaggerated, in my ignorance. I was just thinking about a solution. To place a reinforced truss (double truss?) for the extension along the outer wall of the main building's body. Then handle the forces in the outer walls down towards the foundation beam with the help of a glulam post or extra studs. Then a glulam between the ridge on this reinforced truss and the existing truss in the house. But then the existing truss probably needs to be reinforced a bit and likely something must also be reinforced to handle the downward forces from the existing truss, as the forces increase.
Not quite sure what you mean by load-bearing issues. The inner roof truss will also stand on the outer wall, but that's just in the far corner against the house's gable when I think about it. In other words, at least two roof trusses will rest over the wide entrance to the dining room below, which isn't particularly good
I have to make new higher wall plates anyway since the eave will be too low otherwise, so a glulam beam from the outer corner towards the house body might work if it can be attached somewhere. Maybe it is possible to take out a hole in the old plank wall and slide it in a bit?
I have to make new higher wall plates anyway since the eave will be too low otherwise, so a glulam beam from the outer corner towards the house body might work if it can be attached somewhere. Maybe it is possible to take out a hole in the old plank wall and slide it in a bit?
Buy real rafters with a lower frame, saw in a reinforcement in the wall.
Possibly a steel beam that you embed in the lower frame.
Possibly a steel beam that you embed in the lower frame.
Here is some more info about the build:cust3000 said:
http://www.byggahus.se/forum/socialt-projekt/139006-utbyggnad-i-mariestad.html
Then Marlene has also written an article:
https://www.byggahus.se/bygga/byggde-3000-per-kvm
Oh, what a construction! Our project will be quite small compared to yours. Good tip with the custom-built small trusses. One thing that will be tricky with our house is that the old roof must be removed before the trusses can be installed, so it's important to choose a period with little rain
Yes, this doesn't make it any easier. As you can see in the picture, I took some time to saw small custom holes in the existing roof deck for the struts, just to keep the old roof as rainproof as possible while the new one was being built. When the new roof was ready and the valleys were tight, I cut an opening between the new and the old attic, so today there's an opportunity to go between them.Peter_K said:One thing that will be difficult with our house is that the old roof must be removed before the trusses can be installed, so it's important to choose a period with little rain