I would like to build two dormers, but I won't get new building permits for a few years. I can make an "Attefall" dormer already, but it will be too small if I have to stay between two roof trusses. Is there anything preventing me from making a larger dormer where I keep the roof truss in the middle for the time being? Then I wouldn't have affected the construction and it should fall under the framework of only a building notification and not building permit? Then in a few years, I can apply for a building permit for the dormer instead, and remove the truss in the middle. Since the plan from the start is to relieve a truss I can do that already when I build it. Later I can just cut away the light blue at any time. After the building permit, that is...
Do you see any problems with doing it this way? I've attached a picture of how I envision it. I don't know much about roof constructions yet so I've only sketched the principle a little. Maybe the trusses for the dormer should be made more like an A-model (collar beam?) so that the load rests more on the green beams instead of the little that's left of the cut truss? I've mostly drawn it this way to get more headroom. It is only 190 cm at the middle today in the rest of the loft. I think the trusses on the house look like I've drawn. I haven't wanted to open it up and check the details before getting approval to continue.
The red is what should reinforce/compensate for the disappearance of the light blue. The idea is that you should be able to cut the light blue at any time, with just a little impact on the interior surfaces locally.
The distance today is about 95 cm between the roof trusses. The collar beam at the bottom is a little over 50*170 mm. The one above I don't know. The slanted beams I don't know either, just guessing they are 50*170 mm too? Metal roof.
What do you think about my idea? This will then be copied to the other end of the house.
I have no opinion on the legal aspects. However, when looking at the constructive issues, I have some objections to your solution.
When constructing a dormer that is two truss widths wide, you cut off the middle truss (the one you have marked in light blue) and replace it with a beam to the adjacent trusses. These then have to take care of the roof load that would otherwise be on the middle truss. After checking whether the existing trusses can handle the additional load, you might need to reinforce them. Such reinforcement should primarily focus on the rafters. Important parameters in this regard, besides the dimensions of the involved surfaces, are the roof pitch and snow zone.
I've drawn the beam, the horizontal red one? Even though I don't know how the beam should be attached/angled.
What's left is the reinforcement of the high beam? Is it enough to do it on the side the dormer is on? It's a shame to tear up the other half of the roof.
Do you normally reinforce by adding another beam under the existing one? It's doable when you're opening everything up anyway.
Is there any issue with finishing everything and as a last step just cutting the light grey in the future? Normally you'd cut the truss before building the dormer itself (I assume).
I would not do anything like that without calculating it (or hiring someone who can do it). It's only the high studs on the side of the dormer that might need reinforcement. A high stud can be reinforced in different ways depending on what is practical. Ideally, you should both glue and screw, either on the side or from underneath. It's fine to save the cutting of the main rafter for a later time.
Okay, let's see if I can learn how to calculate or find someone who can do it for me. If there are no issues with my ideas, I can make the construction notification in parallel for now, as it doesn't include any changes to the roof trusses.
Realized that reinforcing from below won't be so good as it would make the ceiling too low, but from the side would work.
Came up with something now... Do you think it could be a problem to do this within Attefall anyway? My idea was to remove the middle truss and relieve this later in the process, even if all preparations are made now. But even now, won't the dormer and its roof mainly load the outer trusses, a surface that was previously distributed evenly over three trusses? Isn't there a risk then that I have to reinforce the outer trusses already now and that it then doesn't fall within Attefall?
Or should the existing outer trusses manage this as long as you keep the one in the middle? It depends on what you state the existing roof dimensions are... Now I'm going to reinforce it anyway, but the problem is that everything has to fall within Attefall since they refuse building permits.
Reinforcing the trusses also means a change in the load-bearing structure, right? Even if relieving it is mainly what one thinks about.
What do you think about this variant I've made? The purple parts are what I see as the most critical, and the red parts are reinforcements. The high beam in the middle will be removed later. The gray/white in the background is just existing interior walls/ceiling.
In the zoom-in, I've drawn a red beam that offloads between the trusses, just as described in the book "Bygga tak" by Per Hemgren. It only seems to be cut out for the truss and nothing more. Do you think that's enough? I recall reading elsewhere here that there's typically a beam angled horizontally and one vertically. But no need to complicate things if unnecessary. It shouldn't be too complex when only one truss is removed, I've read...
Existing trusses have a lower part approximately 170*50mm and a high leg of 150*50mm, with an overlay of 70*50mm for an air gap. I don't seem to have a collar tie; it's three boards nailed at the top (not easy to see exactly before tearing down). The trusses are about 95 cm apart. Snow load zone 2.
Is it unnecessary to reinforce the standing outer corner of the dormer as I've drawn it double? Or is it just good, and should I also reinforce above the window with another parallel as the dormer's roof rests there?
I haven't contacted an engineer yet. Partly because I don't know how, but mostly because I want to get approval to build before I pay for an engineer regarding dimensions. They could claim that the dormer is too large, which seems to be a matter of judgment under the Attefall rules.
Would be fun to hear how it has gone for you and your application. The size of the dormer shouldn't be a problem in itself since the width << 1/2 of the roof's width. And it's fundamentally interesting to understand if, for example, when constructing new buildings, one can "prepare" roof trusses/roof structure for attefall dormers.
One more question. If you are thinking about building a new house today, could you from the start, at the building permit stage, design a load-bearing roof truss solution where there are practically no trusses in the way for where you plan the attic dormer in step 2 if it is later, say, 3-4m wide?
One more question. If you're thinking about building a new house today, could you from the start, when applying for a building permit, design a load-bearing roof truss solution where there are practically no trusses in the way for where you plan to add the Attefall dormer in step 2 if it's later, say, 3-4m wide?
I haven't gotten around to filing any application yet. However, the plan is to build during the spring, unless I'm too optimistic about how long it takes to get a building application approved. I've been taking it easy since I realized nothing was going to happen this year anyway.
However, I probably won't follow the original plan. For some reason, there is about 120 cm between the rafters in one place (elsewhere just under 90 cm), so I'll probably stick to those measurements and insulate outwardly, so nothing is lost indoors, possibly just the width of a drywall.
I think it will look nicer without overly dominant dormers, even though it's, of course, a bit disappointing that it will be slightly smaller indoors. The municipality seems to regard it as their main task to find reasons to deny building permits/applications, so they were, of course, negative when I emailed and asked how they reasoned regarding my first proposal, which this thread is about. However, they said I was welcome to apply to have it officially processed. It would have been interesting to see what they would cite as a reason for denial, but I think I'll skip that process anyway. The "funny" thing is that in two years, when a new zoning plan comes into effect, it will be possible to build large dormers but with a building permit instead.
As Alexn72 says, it shouldn't be a problem to start building in a certain way in advance. I seem to have read something here about someone who applied for a building permit just to relieve a rafter. Then after that, they were able to build a dormer under attic regulations. I have no idea myself how this works, if it's permissible to make such "weird" building permits or if it varies between municipalities.
Hello, I know the thread has been dead for 2 years, but how did your project go? I have a similar one and am curious if it requires a building permit or not. I will need, just like you, to go over 2 arches and will need to remove a leg on the truss just as you drew. Anyway, feel free to send a message if you see this. Grateful for a response.
No, I haven't built anything yet; I've just applied for a building permit for a larger extension, which would make the upper floor "superfluous." But if I get denied, roof dormers might become relevant again. A building permit is needed if you're modifying a roof truss, but otherwise, an "attefall" is sufficient. My problem was that I couldn't apply for a building permit until now.
Member "guggen" here on the forum sent me nice pictures and a description in a PM about how he made his roof dormer. If he looks in his outbox, maybe he can send the same to you.
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