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Planning a Japanese inspired garden shed

Started by GRadice, February 13, 2021, 05:37:35 PM

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JRWoodchuck

Hopefully you chose the copper panels. Really bring the building together!
Home built bandsaw mill still trying find the owners manual!

GRadice

Well, the copper was a bit over my budget and I was worried about thieves stealing it. I went with terne (modern terne is tin covered stainless steel) which should last 100 years or more, was about half what copper costs, and shouldn't attract thieves. It patinas to soft gray which should look good with weathered wood.

I've started in on the mortises for the connecting boards that collectively are called nuki. They are similar functionally to girts but are thinner and taller and there are more of them than there are girts in western timber frame. The multiples provide the racking resistance that knee braces provide in Western construction. The nuki are colored tan.



 

These are sometimes layed out on the same plane and joined with half height mortise and tenons that overlap at the corner posts. I chose the other option which is to stagger the heights and use wedged half dovetails since I think they are stronger in tension. Although that does remove a little  more wood from the post. Here is one mortise done with a test half dovetail in scrap.









And assembled, but with the post horizontal since I was working on it.



 

There are lots of ways to make mortises. I chose to make a router template that registers with the centerline and use a router with collar to rout to a depth of 16 mm/5/8". That established housing for the nuki and also established a consistent reference for paring the mortise sides square to the surface. Then I augered out much of the waste. Mortises are a nominal 30 mm and the auger is 28 mm which gave me a little room for error in drilling without leaving too much waste to pare. The additional block sitting on top was to gauge the depth. When the drill chuck reached the level of the block I was done.



 

 

I have the mortises all routed and a few left to drill out. Then I'll go on to chopping and paring them square.



Gary

JRWoodchuck

I'm a roofing contractor in Eastern Oregon and had a client last summer that wanted copper drip edge and valleys. That bill was 9000 for materials.... So I get not going copper I was more joking about the roofing. 
Home built bandsaw mill still trying find the owners manual!

GRadice

Then you'll like this: for fun I inquired about getting copper shingles, flashing, and ridge cap from a supplier in Japan. The total cost with shipping would have been close to $10,000 per square. The rep and I had a good laugh about that, too!
Gary

Tom King

Interesting that they are calling the tin coated stainless Terne. 

There was a company here that sold what they called Terne coated metal for roofing.  It was tin and lead covered regular steel, and had to be painted.  All that I ever knew anything about was standing seam. 

The roofs were commonly called Terne tin, which got changed to being called "turned tin" by most people that didn't understand the brand name being called.  A lot of people, including some historical "experts" still call a standing seam roof "Turned Tin".

That company was Follansbee Steel, and I think went out of business in 2012, put under by the snap together standing seam roofing.

GRadice

This version of terne is made by Roofinox, which I believe is a German manufacturer. This gives some of the history and different combinations of metals used to make tern over the years.

https://www.roofinox.com/us/for-builders-renovators/terne-for-historical-buildings/


Gary

GRadice

Anyone have experience using Japanese framing squares?

I am less than an amateur with Western framing squares so I can't really compare them. But I'm getting the hang of the Japanese square, called a sashigane or 指矩. I have a few of different sizes. These two are sizes that are most comparable to my old Stanley square.



 
 

I also have one that is about 6 inches long and one that is about 4 inches long. Those are great for checking mortise walls for square.


Sashigane come with various rules, including shaku system on both sides, metric on both sides, shaku one side and metric the other side, metric and inch scale. In Japan it seems it is still common to use the shaku system in construction layout but materials come in the metric system so they need both. Just like here we mostly lay out in inches and feet but sheet goods tend to come in metric. You have to learn both. In fact Chris Hall convinced the Shinwa corporation, the leading maker of measurement tools in Japan, to make a sashigane in inches and centimeters to be most useful in the West. The standard rules are used both for layout and to calculate and measure angles for roof framing, as in the West.

In addition to regular rule measure in each system, some sashigane come with an additional scale that is the rule times the square root of 2. That is mostly used to calculate the largest beam than can be sawn from a round log. Youtube has videos of that being done. Some have a third set of gradations that is the rule times pi. That is used to measure a circumference give the diameter of a circle. I guess if you are using round logs that would be helpful.

Here is one video of sashigane in use, including a clever way to use them as winding sticks. But they have other layout uses for timber framing

The Use of Tools ’Ruler’ / Takenaka Carpentry Tools Museum Video Library - YouTube


I will also say that their slim dimensions lets me use them as drafting tools.


Gary

JRWoodchuck

Every fall I spend a fair amount of time on eBay adding to my Japanese tool collection. The sashigane is on the list but haven't purchased one yet. Been buying planes and chisels. Slowly figuring out what's worth my time or not. 
Home built bandsaw mill still trying find the owners manual!

GRadice

You didn't ask but depending on what you would use it for, I'd suggest starting with the 30 cm/1 ft version and think of it as combination square rather than a framing square. Large enough to use for timber layout and small enough to use for furniture making and drafting. They cost about $11 dollars new so a small investment to see whether you find it useful. You might have to tweak it for square but I don't find that difficult to do.

Incremental progress. I got all the mortises cut on two posts. One of the corner posts here.





I did have one layout glitch that led to a cutting glitch that required patching. However, I can't seem to find a picture of that.....

Each post seems to be taking me a couple of days to get the mortises chopped. I have four more to go then on to the mortises in the beams.
Gary

GRadice

More slow progress. But as I heard a guy say recently, "Sometimes slow is as fast as you can go."

Part of the slow progress is because I dropped my slick on a concrete floor and of course it landed on the cutting edge. Not catastrophic, but chipped enough that it took me about 3 hours to re-sharpen. Penance.

I thought I would show this new-to-me way to peg tenons that I learned recently from an American who just finished a short apprenticeship in Japan with a company that does traditional Japanese carpentry.

Japanese traditionally use square rather than round pegs and also traditionally orient the peg square to the posts and beams. But Japan is also earthquake country and they spend time thinking about timber framing and earthquake resistance. Recently some group in Japan did a test of how resistant to tension were various ways to peg M&T joints and the winner was a new one. The essential features are that the square peg is rotated 45 degrees, and a kerf is cut in the end of the tenon. Here are the two versions:



 

The way it works is that the peg is slightly draw bored as usual. But when the peg is rotated 45 degrees and the tenon is kerfed, the peg slightly expands and wedges the tenon into its mortise. If tension increases on the horizontal beam, the tenon wedges more tightly and resists shear on the relish even more.

I have not seen the engineering data but intuitively this seems like a brilliant twist (ha!) on a centuries old joint. Or, maybe it has been thought of before and I just missed it.

In any case, I decided to jump in with both feet and use this on my shed for the floor beams to corner posts joint. In my case I also have overlapped the  tenons that meet at right angles on the post and have housed stub tenons to further support the beam and resist twist when the floor is loaded. This post is almost done:



 

 

 



Gary

JRWoodchuck

I appreciate any input especially from someone that has experience with the product. It seemed like the last time I looked they were $60 ish and I have plenty of functioning squares. But at $11 ish that makes it much more feasible. 
Home built bandsaw mill still trying find the owners manual!

GRadice

Right, the full sized sashigane are about $60 but the mid sized versions are much cheaper. I find the 30 cm/1 ft (long arm) version is fine for 95% of what I'm doing with this build. I'm using the metric/metric version without the square root or radius functions. If I was doing hip roof layouts I might go with one with a square root measure as well.

I was making good progress on the joinery but this weekend we brought home a little girl who will be taking up some extra time for awhile. My new bench dog, "Willa".



 






Gary

Walnut Beast


realzed

She's a real cutie - I bet she'll be a real 'going concern' in a couple of weeks..
Is Willa a Golden or Yellow Lab?
Either way that will be a perfect spot for her - they love to carry sticks of wood around all of the time!

GRadice

Golden retriever, just over 9 weeks old. Yeah, pretty cute.



 
Gary

realzed

We've had a couple and they are beautiful companions - very intelligent and trainable, but high energy for the next year and a half for you I would bet until she slows down!
The colour of her ears now, will be a pretty accurate indicator of what her colour will be when she matures.
I showed the picture to my wife and it brought tears to her eyes - remembering the ones we had - you get so attached to them that I don't consider that we could fathom ever getting another..
My wife's first comment was "ohho here comes trouble, keep anything wood related out of reach or it will be gone"..  :D

GRadice

Despite the new puppy I've made some progress. I finished the 28 post mortises and am on to the three way joint between the tenons on the post tops, tie beams on the short axis of the shed, and eave beams on the long axis. This joinery pattern is called oriokigumi 折置組 and is/was used mostly for barns. Here is a picture from a book of joinery models. The tie beam sits on the post.



 


A stepped tenon on the post top rises through mortises in the tie beam and eave beam. The joint between the tie and eave beam is a cogged lap, called a watariago joint in Japanese. It is supposed to be as strong as a half lap joint but removes less wood. I can't confirm that but it's what I'm doing.

I started on the tie beam. I did the mortise first using a drill and chisels, checking for square. Then saws, chisels, and a router or router plane. I'm still working out the best method for my skills and tooling and tolerance for noise and mess vs speed. The bevel in the corner is to accommodate a chamfer on the the eave beam.



 


Gary

JRWoodchuck

I'm really enjoying this thread! Thanks for bringing us along!
Home built bandsaw mill still trying find the owners manual!

GRadice

Thanks for the feedback. I'm having fun trying to figure it all out. 
Gary

GRadice

I finished the joinery for three tie/cross beams. The mortises in the centers of the beams are for the equivalent of king posts.



 


Edit: the beams are the ones shown here in brown.



Gary

GRadice

Rather than complete the joinery for the post/tie/eave I've moved on to the joinery for the floor beams. Only because I already have them in my shop and moving the posts or eave beams would be a big hassle.

I started with one of the floor beams in the back of the shed since if I screw up my mistakes there will mostly be hidden. First off is one of the beams that will have a three-way joint.



 

Here is the right end of that beam. It will receive a long tenon from the floor beam to the right and be tightened down by wedges that insert into those half arrow mortises. I showed the joint model way up thread.



 

And the other end of the beam has a haunched tenon, some stub tenons, an unusual square peg that is rotated 45 degrees, and a kerf. The haunch and stub tenons resist twist without removing too much wood from the post and also help support load on the beam. The rotated peg and kerf is, I think, genius.

I found this way of pegging tenons in a blog post by Jon Billing, an American who worked for a time with Somakosha, a Japanese construction company that builds using modern versions of old Japanese methods. The link describes using it for furniture but it was born in timber framing.

https://www.bigsandwoodworking.com/maruta-bench-build-3/

Under tension, the tenon will tend to spread and increase resistance since it will be under compression. It will act more like a dovetail. Here is a sketch of the beam in my shed.



 

And here I am today. I haven't chopped the peg mortise yet. It needs to be draw bored and I am waiting to get all the other joinery done and test fit first.



 



Gary

GRadice

I finished the second of two "rod tenon mortises" (a rough translation). This one is a little better than my first.



 

There is a subtle feature that the two little half mortises for the locking keys need to be tapered along their depth. I haven't been able to find a good description of how to layout out and cut these in English but I do have a drawing by a Japanese carpentry master name Shinzo Togashi that gives a clue that the tapers should be about 1/20th the width of the beam. In my case about 5-6 mm.



 

Here is one layout and finished half mortise. Chris Hall mentions that because of the taper in one dimension, ideally the key needs to be tapered in the other dimension as well but the second taper is very small.

 


 




Gary

JRWoodchuck

Man those look like they are a bear to cut!
Home built bandsaw mill still trying find the owners manual!

GRadice

The tricky part for me is finding a way to cleanly cut the right angled part of the wedge mortise. I tried different ways and think a small, fine saw is the way to go. I don't have a woodworking saw, either English or Japanese, that is fine enough and small enough to fit into the joint. I ended up using a piece of hacksaw blade. Once that cut is done, however you do it, the rest is all paring and pretty simple.

Dorian Bracht has a video showing how to cut a similar joint with just a chisel. I tried that it works but if your wood is at all squirrely it can get ugly.

Random Joint Investigation Ep.2: Yatoi Hozo (雇ほぞ)/ Draw Pinned Spline Tenon (Japanese Joinery) - YouTube

This joint and variations of it are very common in Japanese construction. It is much stronger in tension than a pegged tenon and there is virtually no chance of shear failure or compression failure of the wedges. It can also be easily dismantled if you leave the keys long so they can be pulled back out. Or tapped in and tightened more if the wood posts shrink. But a lot of up front work.
Gary

GRadice

Here is the male part of that mortise.



 

Since that member is only three feet long I cut the cheeks of the tenon on the band saw. Hand saws and chisels for the stub tenons, wedge mortises, and clean up.

As test assembled. The gap between the beams is where they insert into a post.



 

And a detail of the half mortises for the tapered wedges.



 

I am making the wedges parallelograms in sections. They can be made rectangular but that tends to spread the joint. Maybe not a big deal on wide beams. Parallelogram wedges are a little harder to make but are a better solution. Here are the two options from Chris Hall's masterful monograph on Japanese splicing joints.



 

 

 
Gary

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