Sauna Design - Need Feedback

[jander3]

Over the winter I plan to frame up a small sauna with a covered porch for the house. I've made a few log structures with mortise and tenon joints and made a number of timber framed tables to practice my joinery.  This is the first framed building I've tackled, so I decided to keep it very small and simple.  I would appreciate your feedback or suggestions to improve the design.  I've provided my thoughts and questions below:

I plan to use 6" x 6" or 6" x 8" timbers.  I'm located in Minnesota, so the snow load is about 45 psi.

On the front (bent) view, what is the easiest joint I could use to secure the tie beam to the posts. Would a standard mortise and tenon with, say a 3/4" shoulder, work?  Or, do I need some type of through mortise with a dovetail and wedge?  I want to make sure the ridge load is transferred to the posts. 

If needed I could drop a center post down to the planet on the middle bent and offset the door to the sauna.  With the size of this building, that post doesn't appear to be needed.  Any thoughts?

Is there a better design I could use to support the ridge?

Is there a standard size for knee bracing?  I was planning on using 3" x 5" stock.

[Jim_Rogers]

With the rafter sitting on the ridge beam there won't be much outward thrust of the rafter at the plate.
However a straight (not dovetailed) through tenon would be the best to make sure you have enough relish on the tenon for the peg hole. And yes with a shoulder for the tie beam to the post, for sure

You should plan on some type of rafter to rafter connection, such as a tongue and fork joint. Or if not then some type of long screw will be needed to secure the rafter to the plate.

If all three bents are going to have a short post supporting the ridge beam then the roof area being place on the center of each tie beam won't be real great, but someone should check the math and see if it is ok for a 6x6 if not then the 6x8. Also you need to say what type of wood you'll be using for these timbers.

[ljmathias]

And with snow, your slope doesn't look steep enough: what kind of roofing are you planning on using?  Anything below 3-12 and your limited to metal (at the high end) and rolled roofing at the low to flat end.  Make it steeper and you win- 5-12 is a great compromise: you can still walk it easily and metal works fantastic- looks good, lasts for 40 years and is easy to do in a day on your size structure.  Also, don't forget the overhang all around: the more the better up to a point: keeps the weather off the siding and out of the building...

Lj

[moonhill]

I am assuming the material will come off your land.  The ridge is the major carrying member and will be additionally supported by the center tie, the ends can have post under them.  All the dimensions in this building are small, with the exception of the 17' ridge.  Make the center tie larger to carry the sag of the ridge.  You could use a crooked piece for the center tie, to make things more interesting.

As for the rafters, they are only 3.5' between supporting members, I see no need to increase the slope, a flat roof could handle the load, but you want the water to run off, nicely.   I would even suggest skipping the rafters and deck the roof with 2" planks, hew a bevel on the top plates and ridge. 

Are you insulating this sauna?  How is it enclosed?

Tim

[jander3]

Thanks for your thoughts. 

Jim, I appreciate the through mortise suggestion, I will use that. 

Ljmathis the roof slope is low so the sauna will heat up nicely.   I'm 6' 5" tall, I want to be able to stand up inside the sauna so the tie beam has to be 6' 6", I compensated with a lower slope on the roof.

Moonhill, actually I am having these timbers cut by a local sawyer.   This sauna is for our house in the city (goes with the hot tub). The sauna will be insulated.  Outside will be enclosed with some type of live edge siding.   I have not figured out the inside. I would like to infill and leave the beams exposed; however, I may have to cover everything up with tongue and groove.  A larger tie in the center is a good idea.