Planning a Japanese inspired garden shed

[GRadice]

Something a little different. This will be small, just 6'x9' and about 12' tall at the ridge. Port Orford cedar posts, beams, and siding. Probably Douglas fir for the other framing members, Oregon white oak floor. Posts scribed to stone. Traditional Japanese joinery. It will face south and there will be some glazing to take advantage of natural light. No utilities or insulation. We will use it as a potting shed but in the future it could be used as a child's playhouse or maybe a small studio in mild weather.

POC has been ordered. Sawmill tells me it should be dry enough to begin working it in late summer.

Here are some conceptual sketches. I'm working on the roof design and joinery details now.
I'd be happy to hear suggestions since I still have a few months before chips fly.


 

 

[Sod saw]

Hi GRadice,

I enjoyed looking at your sketches.  It looks as though you are on your way to a nice shed.

My Dad was an architect, here in NY,  who was influenced by; and while stationed in Japan during WW II.  Many of his houses as well as NY State Park System bath houses, etc. have the result of that influence.

One very easy and simple trick for your shed might be to cut the rafter tails slightly to resemble the upturn of their overhangs.  This can be done without changing the top edge of the rafter thereby saving you the trouble of having to shingle a valley near the end of the overhang.

That rafter tail cut works well if not level.  It should still have a slight pitch down towards the tail end allowing rain to drip off the end and not run back towards the building wall.  Starting that cut about 1/4 to 1/3 of the way to the building outside wall will allow the rafter to show the roof pitch and still have that up turned effect.

I have drawn a sketch detail. (Sorry but I use Dads drafting table as I do not have fancy computer programs)  Hope this helps to explain somewhat.




 





Another item to look at is the pitch of the roof.  If you keep the ridge low and therefore the pitch as low as you can without allowing the roof to leak, you will enforce the overhang feeling.  But, a flat roof would not work as well as one with a slight pitch.  I wonder, with shallow pitch, perhaps the depth of the rafter should be increased slightly.  

In my opinion, the gable ends should also have the same overhang distance from the building wall.  Sometimes it is tricky to support that overhang without ending up with a bulky looking job up under the roof.  Keeping it dainty looking goes towards the overall feeling and looks of the whole project.

There are some other ratios and rules of thumb that should be kept in mind when working with larger overhangs.  Perhaps Don P can chime in here.

Have fun with it!

 

[GRadice]

Thanks looking and for taking the time to make the drawing. There are lots of little details to consider like the rafter end that you suggested that to me make a big difference. In one of the books on Japanese carpentry I've been reading, the author said that there several ways to finish a particular dimension and angle and that carpenters can make different choices depending on the situation but that the result should appear "serene." I love that.

I'll add that I'm approaching this from a furniture making background so I might overthink the joinery a bit.

As far as the degree of overhang, I'm working with multiples of 12" centers for the rafters so the gable end will probably be plus or minus 24" and the eave ends will be around that as well.

This is still all silicon, electrons, and neurons at this point so any other advice is welcome.

[GRadice]

It has been a year and the shed is still in progress. I bought the POC beams last winter, then gave them their relief kerf to limit surface checking mostly to one surface.



 

Then restacked the beams to dry outside under cover.

Over the summer I refined the design and made a joinery model. The joints are proportionally correct but scaled to fit the model into my shop so the posts and beams are much shorter proportionaly than they will be. In other words, this is not a scale model of the shed, but it is a scale model of the joints.



 

One fun part was working out the joinery for the barge boards to the eave beams and ridge beam. The joint uses a yatoi hozo, which is a tenon with a dovetail on one end and tapered wedges to pull it tight.


 
And here is the joinery for the floor beams to posts.





 

 
I also dug holes for the concrete piers. I embedded stainless threaded rod, and bored holes into river rocks to fit over the rod. The posts for the shed will be scribed to those rocks.



 

In January I brought the 6 posts into the garage to dry further. They were cut at 6x6 and after a year outside they were at about 15% MC.  I started milling them square and straight but I'm leaving them oversized while they finish drying in case they move. I'll show how I'm doing that in the next post.

[flyingparks]

 

[aigheadish]

For real. This is neat! Those joints look nuts!

[GRadice]

I have 18 posts and beams to process. 15 of them are 10' or 8', three are 14'. I'm starting with the 10' posts, rough sawn to 6x6.

Japanese framing generally uses much slenderer members than is common in the West. Posts for a one story building are standardized at 120 mm x 120 mm (about 4.75" x 4.75"). That means that makes the timbers easier for one person to manipulate and makes it possible, if barely, to take the beams to the tool for processing.

So my strategy for working the beams down to finish dimension is to first knock off high spots with a power planer, then run the nearly flat beam over my 12" jointer to join two adjacent surfaces. My garage is 20'-8" wide and the jointer cutterhead is right in the middle so I have 10'-4" on each side. Just enough to run the beams, with the help of some shop made infeed and outfeed rollers.



 

Then I haul the beam over to my 26' bandsaw running a 1" carbide tipped blade to cut the other two sides. I rigged a long torsion box outfeed table to the bandsaw. I actually have two bandsaws but I'm using the second one here just to support the outboard end of the outfeed table. Small garage shop, ya gotta be efficient with space and tools.





Low and behold, it works.



 

The 14' beams will have to be joined with a circular saw and power planer but I can still bandsaw them.

The posts aren't dry enough to cut joinery yet. As I mentioned they are at about 13-14% MC. My plan is to leave them oversized (they are about 135mm square now) until they get to about 11-12% and then work them to finished dimension. Our rainy season here in Oregon will end in May. I hope to be able cut joinery over the summer and get this thing in the air and covered before the rain starts again in October. Fingers crossed.

[GRadice]

A little more progress. The posts are down to about 12% MC and I have worked them to a couple of mm over their finished dimension of 120x120mm. I also decided to fill their relief kerfs using some of the cutoffs from resawing the posts. This was mostly an esthetic choice. If I was insulating the shed the kerfs would be buried in the walls and I would leave them open, but I'm not so these will be exposed and I decided I liked the way they look filled better.




 


I also worked down the floor beams and roof tie beams to just over final dimension. You can see them to the right. Those have been outdoors and are at ~14-15% MC so I'll wait a little longer before working them to final sizes.

The posts are just about ready for joinery. My plan is to first cut mortises and drill holes in the feet for the threaded rod and access for the nut to hold them down to the stones. Then erect and plumb the posts and scribe them to their stones and carve them to fit. Then shoot a level line for locating the floor and other joinery.

[flyingparks]

Very cool! I relief cut...nice. 

[GRadice]

Finally after almost two years I get to do some layout and cut my first mortises.

Japanese timber framing is layed out from center lines. Center lines are inked. I'm using a Tajima InkRite and Tajima black ink. All four faces will have their center lines marked.



 



 

Then I layed out, drilled, and chopped mortises that provide access to the threaded rod that will lock the posts onto their stones.


 



 

Then drilled out the hole for the threaded rod. I made a guide bushing first and clamped that to the post.



 

That got the hole centered. I left enough room, I think, for the washer, the nut, the threaded rod, and a finger to two to get the nut started.



 

I have two posts done. After I do the other four I'll be able to set them on their stones for scribing and carving. The mortises will be plugged and planed flush after the shed is all assembled.

[aigheadish]

I admire your patience and skill. This is an incredible project!

[timberframe]

Finally after almost two years I get to do some layout and cut my first mortises.

Japanese timber framing is layed out from center lines. Center lines are inked. I'm using a Tajima InkRite and Tajima black ink. All four faces will have their center lines marked.


(Image hidden from quote, click to view.)
 


(Image hidden from quote, click to view.)
 

Then I layed out, drilled, and chopped mortises that provide access to the threaded rod that will lock the posts onto their stones.

(Image hidden from quote, click to view.)
 


(Image hidden from quote, click to view.)
 

Then drilled out the hole for the threaded rod. I made a guide bushing first and clamped that to the post.


(Image hidden from quote, click to view.)
 

That got the hole centered. I left enough room, I think, for the washer, the nut, the threaded rod, and a finger to two to get the nut started.


(Image hidden from quote, click to view.)
 

I have two posts done. After I do the other four I'll be able to set them on their stones for scribing and carving. The mortises will be plugged and planed flush after the shed is all assembled.

Line rule!  Very nice.
B

[rusticretreater]

Fine work!  How are you going to tighten the nut? It looks pretty snug inside there.

[ljohnsaw]

 

[JRWoodchuck]

That’s a nice looking hand hammered hoop on that nomi. The joinery is ridiculous as well! 

[GRadice]

Fine work!  How are you going to tighten the nut? It looks pretty snug inside there.

There is just enough room for the nut and the plate washer, and two fingers. I checked! I do wish I had used 5/8" threaded rod instead of 3/4".
Next up is scribing and carving the post feet to their stones. A friend who does this kind of work told me that figuring how to do this efficiently "is a creative endeavor." He recommended using scaffolding to support the post when it was plumbed rather than try to screw braces to it, because you have to set the post, scribe, dismount it, carve, reset to check your work, and repeat until you have a good fit. Not so easy with a 60 pound post 10 feet long.
I made some shipyard staging horses out of 2x4's and 1x6s. I got the idea from the Bristol Shipwrights on youtube. The scaffold board is a 2x12 x 12'. To that I clamped an L-shaped cradle that would support and register the upper half of the post when I had it sitting on the threaded rod and plumb. To check that the posts were square to each other I made some mini-posts of the same dimension and the real post and ran a dry line around them all. Then I adjusted the post and minis until they were all square to each other (no gaps in the dry line) and tightened the minis down as my reference. I'm sure there are other ways to do this using batter boards and such but I did it this way.


 
To check for plumb I used a 4' long shop made version of Japanese plumb line level. Very simple, very effective. I fastened it to the post with a bungie cord. That made it easy to flip to the other face of the post and left my hands free to adjust plumb. I chalked the stone to transfer contact points to the post.


 

 
Then chopped away. Most of the work is done with a Japanese in-cannel gouge (sotomaru nomi). These are great because they can be sharpened on a regular flat stone. For carving I set the post(s) on a couple of low sawhorses. The dowel is there to prevent blowout around the hole for the threaded rod while I'm carving. The towel is for my butt. I also found it more comfortable to sit on two posts.


 

 
And one post done. I'll wash off the chalk later. Five more to go.


 

 
Other notes: I covered the site with 3/4" minus gravel to keep the dust and mud down. It will get covered when the shed is done with more attractive pea gravel. The rugs are to keep gravel off of the posts.

[GRadice]

Four posts done. Two to go. For scribing I'm using these simple and cheap washers CYA glued to each other and a small nut. It works as long as the stone has smooth transitions, which mine do. Much easier than scribing with a compass. I made several sizes depending on the gap I needed.




 

The site. I just added a pop up canopy so I can work in the shade. Worth it. 





  

[aigheadish]

Incredible scribing work! I'm envious of your patience, skills, and technique! 

[GRadice]

Thanks. I don't find the scribing and carving that difficult technically but yes, it does require patience. The first one took me about 8 hours while was figuring out a work flow. The last one I did took about three hours but still much setting and resetting the post.  I have one more to go today and then I'll finally get to shoot a level line. Then I'll be able to lay out the post joinery. Here's the view this morning from our kitchen window.



 

[thecfarm]

Now that's a project!!