I am working on an extension of the summer cottage which will take the form of a small "house" with a gable roof. The extension stands on posts and the plan is to have a vaulted ceiling with a ridge beam. As I started sketching the floor plan, it turns out that the only sensible placement for the gable window is right under the ridge. So, onto the question, how do I alleviate the intended ridge post so the window can be installed? See images below for proposals and issues.
A. This was the original idea with a ridge beam supported by the post. Okay if it weren't for the window...
B. Here, the ridge post goes down on both sides of the window. But these only rest on the bearer without a supporting post underneath. Is this recommended?
C. Here the ridge post merges in the middle under the window and rests on the post. Unstable? Many thermal bridges?
D. So how do you really do it...?
Here are some measurements:
Roof slope: 23 degrees
Gable width: 5000
Distance between gables (ridge beam length): 3500
Window size: 1200x1300 (WxH)
Height from floor joists to wall's top plate: 2400
Wall stud dimensions: 45x95
Beam on posts: 2 x 45x195, C24
What is a sensible solution to do this and what timber dimensions might be required?
B is the best solution. The columns at the sides of the window give rise to two point loads that come quite close to the middle girder. A single 45x195 C 24 can handle it if it is not loaded in any other way. The beam above the window can be 45x170 C 24 considering the small span. The term "bärlina" is usually used for the third load-bearing level (floorboards = 1, floor joists = 2). Does it also apply here?
Thanks for the response - it sounds great if B works! I forgot to mention that the building is located within snow zone 2.5, but that might not be crucial for your assessment? Oh, and to prevent the floor from being too high, the floor joists are recessed into the floor structure. In other words, the floor joists and beams are at the same level.
He he, well this is a summer cottage located in the Borås area - it can snow so tremendously there. Had a neighbor there who moved in the spring of 2010 after exhausting both himself and the snowblower that winter (yes, he was meticulous, there had to be bare ground on the driveway at any cost). In such winters, there can be 50 cm of snow on the roof when you arrive. With that in mind, I thought it was worth over-dimensioning the support beams a bit..
Here in Halland, there's usually not that much snow. Built a canopy last summer and the most important thing there was to get the drainage right..
I have a couple of additional questions: With one (1) support beam, the support for the ridge post (which goes up to the ridge beam) is only 45 x 90, i.e., only half the cross-sectional area with a 90x90 ridge post. How do you attach the ridge post properly to the support beam in that case?
I'm also considering whether it's better to place two support beams side by side instead. These would then be 90 deep together and thus provide full support for the ridge post. The downside, of course, is that there is little space for insulation there (5 mm with 95-studs + 45 in the installation layer). But shouldn't you be able to reduce the height of the support beams from 170 to 120 mm at the same time (or is that on the margin)? The thermal bridge would then be significantly smaller, but is it acceptable?
With the limited height in question, a 45x95 C 24 timber stud placed on its edge can withstand quite a large load (approximately 36 kN at 0.8 m height). It is the free (= unsecured) height of a column in the weak direction that determines what it can withstand in terms of centric load. You can use regular plate and angle iron for fastening.
