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Thanks for the tip, that's a good option, to glue for instance two 2by6 or 2by8 to get to a desired size/thickness.

I am not Japanese, no, could never pass as that. But been here almost 10 years now. I am originally from Europe, and have often been toying with the thought to go back home. I've got a wife and daughter so it would be a bit of a move, these days especially with covid and all. So we are here temporarily for a long time now. There is a french saying goes something like 'the temporary becomes the permanent', often happens that way doesnt it... How about yourself, from the US?
well, yes, you could do that. but i was thinking more along the lines of flat 2x4's, staggered, glued and clamped. the only thing = are you ok with how they look

ok. the reason i asked = your english is quit good, better than a LOT of americans, non americans seldom accomplish that. btw, i don't care either way, i was just wondering.

yes, from and in the states, outside chitcago. sadly i have not traveled much :sad:
 

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Thanks Hotrodx10, that's a good point of caution. My intended roof would indeed be very light, so I think the deadload (?) would be okay, but I am heavier than 150 lbs so yes that is a point of concern. I maybe could go with sistered 2by4s, or even 2by6s. I will think about it...
Just be aware that for vertical loads, the strength of the beam increases linearly for increases in width (double the width = double the strength), but increases by the square (exponential of 2) with changes in depth. So, a 2x6 of the same wood is nearly 2.5 times stronger in the larger dimension than a 2x4. Stiffness change is cubed (exponential of 3), so it's also nearly 4 times stiffer.

Also, due to the unlikely potential for 2 or 3 pieces of lumber having a weak point at the same location, for design there's a substantial increase in the allowable strength for design of a beam made up of 2 or 3 pieces (doubled 2x vs. 4x).
 

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Interesting, I guess the rectangular shape would be for aesthetic reasons?
A rectangular shape (standing up tall) has the most efficient cross-sectional properties for typical loads. The additional width for the most part has the aesthetic purpose. For instance a beam's design load might arrive at a 3x6 cross-section, met with (2) 2x6s sistered. If using a single 6x6 member the 3" in extra width (and weight) is just for aesthetics. But in certain instances that extra 3" in weight might increase rotational tendencies and bump you up to a 8" deep cross-section. Generalized and cherry-picked just to explain.
 

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Discussion Starter #24
A rectangular shape (standing up tall) has the most efficient cross-sectional properties for typical loads. The additional width for the most part has the aesthetic purpose. For instance a beam's design load might arrive at a 3x6 cross-section, met with (2) 2x6s sistered. If using a single 6x6 member the 3" in extra width (and weight) is just for aesthetics. But in certain instances that extra 3" in weight might increase rotational tendencies and bump you up to a 8" deep cross-section. Generalized and cherry-picked just to explain.
Hi 3on,
Thanks. But you're using a lot of terminology I am not sure of the meaning, i.e. cross sectional properties, meaning how much weight it can take? and 'a beam's design load might arrive at a 3x6 cross section, met with 2x6s sistered'. I get the sistered idea, and that you are saying the extra thickness of a large beam adds weight that the entire structure has to be strong enough to accommodate, is it? Care to simplify a bit? I am on a learning curve here..
 

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Hi 3on,
Thanks. But you're using a lot of terminology I am not sure of the meaning, i.e. cross sectional properties, meaning how much weight it can take? and 'a beam's design load might arrive at a 3x6 cross section, met with 2x6s sistered'. I get the sistered idea, and that you are saying the extra thickness of a large beam adds weight that the entire structure has to be strong enough to accommodate, is it? Care to simplify a bit? I am on a learning curve here..

Put his comments together with mine, and an understanding of it should start to form. The "cross-sectional properties" he referred to are the linear and squared properties I referred to. A 2x4 is more than twice as strong when bending in it's 3.5" dimension ("standing up tall" for vertical loads, e.g. the weight of the roof), than if it's laid flat (1.5" dimension vertical).

A pair of 2x6's can carry twice as much weight as one 2x6 across the span between the posts. (The pair of 2x6's can also carry more than twice what a 4x4 will carry across the same span, assuming the same type of wood) The capacity of the posts to carry weight is huge, and not really a concern, but the posts need to be strong enough and anchored well enough for lateral loads (wind).
 

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Hi 3on,
Thanks. But you're using a lot of terminology I am not sure of the meaning
My fault, in my head I was trying to answer a response of "But why" that didn't happen. I should have just said: 4x4s are useless for a beam beyond your arm's length.

For your beam spans, sistering 2x4s wouldn't be adequate either, as HotRod and Neal say, bump up to 4x6 or built-up 2x6 minimum depending on what you cover your roof with. The 2x4 rafters might be a little shy at >10' but could be ok though depending too.

Aesthetics does play a part though, at about 15' long you want the visual "heft" to be proportionate. So 4x4 columns not only will look like toothpicks, but with a roof that size the wind loads (or seismic?) may put undue bending pressure on them.

You have a very unique project. When I see your example design for some reason I think 1890s ice cream pavilion. Have you ever thought about giving a nod to Japan with a simple "iconic" structure, like a kiritsuma or irimoya roof? Irimoya might be slightly more skill but kiritsuma might be cheaper and simpler than the original one.
kiritsuma.jpg irimoya.jpg
 

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Discussion Starter #27
My fault, in my head I was trying to answer a response of "But why" that didn't happen. I should have just said: 4x4s are useless for a beam beyond your arm's length.

For your beam spans, sistering 2x4s wouldn't be adequate either, as HotRod and Neal say, bump up to 4x6 or built-up 2x6 minimum depending on what you cover your roof with. The 2x4 rafters might be a little shy at >10' but could be ok though depending too.

Aesthetics does play a part though, at about 15' long you want the visual "heft" to be proportionate. So 4x4 columns not only will look like toothpicks, but with a roof that size the wind loads (or seismic?) may put undue bending pressure on them.

You have a very unique project. When I see your example design for some reason I think 1890s ice cream pavilion. Have you ever thought about giving a nod to Japan with a simple "iconic" structure, like a kiritsuma or irimoya roof? Irimoya might be slightly more skill but kiritsuma might be cheaper and simpler than the original one.
View attachment 615833 View attachment 615835
Thank you for the additional explanation. It makes sense now. I guess using 10.5x10.5cm hinoki (Japanese cypress) for posts, and same or sistered 2by6s for beams would be better, optically and strength wise, at least. I think I could go with 2by4s for the roof rafters since I want reuse several old corrugated steel sheets I've found in the backyard, that are still in good condition. So that would not be very heavy.

But what is more, I am very interested in your suggestion to giving a 'nod' to my surroundings in Japan and adopt a roof structure inspired by traditional Japanese carpentry. It may be too expensive and difficult but at least I want to explore the option

I can now think of one quite critical initial challenge - would be to figure out the right pitch, height and width of the roof. I want to take the deck 2-3 feet out beyond the corner posts to the front to maximize the size of the deck, and at least part of that should be covered by a roof to protect the oven and deck somewhat against weather. To be symmetrical it should be the same on the rear. But given I am on a slope the roof cannot extend too far our to the sides as then it would get too close to the ground on the up-slope side. I also don't want to take any rain gutters too far from the french drains I've dug to get the water around and away from the area. So those are some guiding limitations.

At the same time I cannot pitch the roof too steep, and I can't make the vertical area of the 'room' (before the roof starts) too steep either because it has to match with the roof height, so I would have to identify that sweet spot and then connect it to a roof that's high enough but not too high. So what I'm trying to say is that I would have to plan around the framework provided by the dimensions and sloping surroundings I've got to work with. I don't know how to do that.

I get the impression you've got experience on that stuff. Can you recommend some guidelines, sample plans, book or point me to information that I can learn from when considering next steps?
 
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