Messing with Sketchup - my cabin idea

[Ljohnsaw]

OK, the concept drawing is off to an engineer to give me a quote to go through it, structurally.

Other to-do's on my list:

1) Go through the hassle of getting the septic installed.  Somewhere between $10k and $40k (if needs to be an "engineered" solution).

2) Get a producing well.

If anyone has any experience and can help me avoid a major expense and time delay:  In their infinite wisdom, California law-makers (since 2010) have determined that requiring a fire suppression system (aka sprinklers) in ALL new construction (residential included) will help prevent structure fires.  Never mind that in the mountains, wildfires are the predominate reason houses burn down!

So this throws a wrench in the works.  My plan was to go solar, which I probably still can do.  I just need to up my battery storage to drive a significant pump load (when called for) for the sprinklers.  That is, unless someone from CA can point me in the direction of a loophole!

Talking with one engineer and my desire to do the timber frame cutting myself - his suggestion was to cut the timbers (slightly oversize) this year and let them dry a bit, finishing the cutting next year.  That would, in his opinion, reduce the problems of various shrinkage occurring because I could only cut so many timbers so fast.  Sound reasonable?

From what I have gathered from this site, I would cut, sticker and stack with a loose cover to protect from direct sun.  When winter comes, completely wrap the stack to keep rain and snow off but somehow allow air flow?  Bear in mind that my piles (5 or 6' high?) would be buried under 6 to 8' of snow before the spring.  Suggestions/guidance?

[Rooster]

How many gallons per minute will you need to push?

How many gallons total?

How many sprinklers?

[Jay C. White Cloud]

Hi John,

Timber frames are built with green wood.  If you are going to wait to build stack and sticker the whole timbers till you can cut the frame in one push.  Joints can distort if cut and stored for a long time, especially using "edge rule", (not so bad with "line rule,"),  To get something even as small as a 4"x6" to "dry out" is going to take a couple of years, and forget your big timbers drying, that ain't go'n happen for a long time, so your PE was a little off on that.

Fire suppression systems are required here in Vermont in some townships for new construction as well.  That is another reason I like the wall truss system, because you can place you plumbing in them easily.  The ceiling is a bit more of a challenge, so I would have to think about it in your case.  We build double and triple roof systems accordingly for homes that require fire suppression.

Best of luck,

jay

[Ljohnsaw]

How many gallons per minute will you need to push?

How many gallons total?

How many sprinklers?

At this point, I don't know.  Waiting for a quote to figure out a design.

Since my floor plan is relatively open, perhaps four (one each bay?) at the peak and one each for the two bedrooms, bath and kitchen (all under the loft area).  That gives a total of 8.  I'm guessing 1/2 GPM each, so 4GPM (about a full blast garden hose).  The PE did mention about 2,000 gallon water requirement to meet code.

One option is to use a "dry" system - there is no water in the sprinkler pipes to freeze when I am away.  This drain-back system then could use a single source of water - the domestic tank.  I just need to figure out a way to prime the pump when needed.  A lot of cabins use a air-pressurized system for the domestic water.  It gets really complicated with freezing temperatures...

[Ljohnsaw]

Hi John,

Timber frames are built with green wood.  If you are going to wait to build stack and sticker the whole timbers till you can cut the frame in one push.  Joints can distort if cut and stored for a long time, especially using "edge rule", (not so bad with "line rule,"),  To get something even as small as a 4"x6" to "dry out" is going to take a couple of years, and forget your big timbers drying, that ain't go'n happen for a long time, so your PE was a little off on that.

<<snip>>

Best of luck,

jay

The PE was NOT suggesting cutting all the joints as I go along.  He was suggesting cutting all the timbers and then the joints.  I was planning on doing that in a modified way. 

Thinking out loud, I figure I will cut all the small stuff (braces) first since I will have about 200 of those, it seems :.  Then I would cut the large stuff to size followed by the joints.

To start out, I figure I should be able to finish one timber a day (4 to 8 "half-joints" each).  At that rate, it would take me about a week to make a bent.  I know I should keep my green wood from drying too fast, so my thought is to complete the 5 bents and do the assembly when I have all the roofing system ready to cover it up - right?

So, even before I start on the timbers, I need to have all my floor joists (2x12s and 5x9s),  rafters (5x9) and planking (2x's T&G) ready to go.  Somewhere in there I will need 2,500 BF of 1x wall boards as well (T&G) as that would go up shortly after the roof.

[Jay C. White Cloud]

 My mistake ;D Yes much better now I understand your strategy.  ;)

Now lets wait and see what the PE has to say about the frame?

[Ljohnsaw]

Now lets wait and see what the PE has to say about the frame?

Well the (first) engineer had a lot to say. 

#1, the "wind bracing" will not even come close to meeting the (California) seismic requirements.  Either cover the entire structure in plywood/osb or have some diagonal steel rods in various places.  I'd rather do the steel (visible) than the ply - a sort of industrial look.

#2, I need to have a plywood sub-floor to meet seismic, even though it is pretty much directly attached to the reinforced concrete foundation!

#3, thanks to a new (2010) building code, I need to have a sprinkler fire suppression system installed!!!  Fortunately, I have a friend in the business that will work with me and do it at cost (~$1,300 instead of $3-6k).

I'm planning on getting two more opinions before I plunk down the money ($10-15k) for the actual work.

Seems that the state-wide seismic code is designed for L.A. or San Francisco, not the high sierras with no earthquakes!

Also, I was visiting my property on Sunday.  I will have to rotate my building 90° due to the limited level building spot.  Now my deck will be on the south side - not so much an issue - but my roof slopes will be facing east/west messing up my solar setup.  Though, I don't need too many panels - maybe have them on the front of the building where I have some blank wall space.  They could even be "awnings" over the windows...  hmmm

[Jay C. White Cloud]

Hey John,

I believe that is what he told you, I even believe he believes it.  However, I think you need to peel a few more layers of the onion back.  That frame, design they way you have it, is way stronger than most stick built structures with their ply wood skin.  I think he is out of his league as a timber frame is concerned and doesn't really know, understand or trust the legitimacy of the architecture.  It is common for us to meet this type of opposition from PE that are not familiar with timber wrights.

I'll share a little story with you, for what it is worth, and maybe you can approach the PE again.  I was part of a project near Paso Robles, CA.  We got the same reaction.  So the entire frame got covered (the wall and roof diaphragms) with two layers of 1" board.  The boards did not go to the sill, so there would be access to a wiring chase.  Then a grid of strategically spaced Kevlar strapping was placed at oblique angles over the frame, staying clear of the projected fenestration of the frame.  It was simple to apply and work with.  When the PE was approached with this solution he still did not want to concede his original solution, (similar to your PE solutions.)  That was until we pointed out that his own firm was using this method on commercial condos in LA with "stick framing."  There is always another solution, and often it is better than what you are offered.

Have you tried:
http://blog.ftet.biz/
Ask for Ben and say I sent you.  He knows timber frames, if he comes to the same conclusion as your current PE, I would except it.  He can think outside the box and always has alternative solutions.

Regards,

jay

[Jim_Rogers]

Firetower is one of the engineers I use, as well.

Jim Rogers

[Ljohnsaw]

Jay & Jim,

Thanks. I'll check them out. I'm in contact with a free-lance engineer who should have time to view my work in a few days. My company used him on some commercial remodel work and I found him to be very knowledgeable and agreeable. He was alway accepting of my ideas. 

[Ljohnsaw]

Jay/Jim,

I had a quick series of emails with Ben at Fire Tower.  What a great guy.  He gave me some additional ideas and some questions to run down with my county.  We Skyped (my first time) so we could real-time discuss the issues.  Unfortunately, my county will not answer my emails (it seems).  I was hoping to get a written trail of their "OKs" to my questions.

The best idea I got from Ben was to use something like Simpson straps on the outside of my braces to provide the necessary seismic strength (tension) while the braces (slightly repositioned as seen below) provide the compression strength.  That way, #1, I don't have to plywood the walls and #2, they are completely hidden.



Yes, if you look closely, those are some deep dado cuts in the sills for the straps.  I will fill the cuts with blocks after nailing in the straps.  The ledge that the sill makes is to support the wall planks and insulation.

[Ljohnsaw]

Firetower is one of the engineers I use, as well.

Jim Rogers

Jim,

I'm curious.  Do they do all your work remotely or do they come on site (on occasion) ?  One question I am tracking down is if the county requires a structural engineer or if a civil can do the work.

Thanks,
John

[Jim_Rogers]

Firetower is one of the engineers I use, as well.

Jim Rogers

Jim,

I'm curious.  Do they do all your work remotely or do they come on site (on occasion) ?  One question I am tracking down is if the county requires a structural engineer or if a civil can do the work.

Thanks,
John

John:
I have only had them do my work remotely.
However I do see them often at conferences and other events.
You can pay them to show up if you need them to do that. They will travel, but it can get expensive to have them there.

What's great about these guys is that they have experience in timber framing.
Some engineers do not. And to educate them you're paying for their education.

Good luck with your project.

Jim Rogers

[Ljohnsaw]

Thank you all on a separate thread on TF Rubies problems.  I got it solved - problem was due in part to my creative thinking.  I have all my separate layers and I constructed parts of my joints on layers that were later hidden so I could generate the shop drawings - and the hidden parts act funny.

So, on to the next step/problem.  I'm green so I need advice from the experts again on my joints.  Pictured below is two typical situations I have in my frame.  Two apposing braces in timbers.  I called them a butt version (in an 8x10) and a bypass (8x10).  Will these work? Enough relish for the pegs? (I didn't show those yet).

The Butt version:


  

  

 

And the Bypass version:


  

  

  

I need to re-read Jim's posts on "timber frame rule" on placement of the pegs - but I think I have enough room/relish for them.

Thanks

[Jay C. White Cloud]

Hi John,

I knew Ben would give you that solution.  I not a 100% sure, but back in this thread I had mentioned "seismic strapping," that we have used, it is a great solution and can even be run in long strips all around the building, it works great!  Glad everything is coming together.

[Rooster]

I vote "butt"...(There's a T-shirt!!!)

This way the diagonals will all be in the same plane, especially on an outside wall where you don't want some of the diagonals to stick out (into the room).

It might make it look like you had too many "negative beverages" at lunch time prior to assembly of the bents.

Rooster

[Jim_Rogers]

Normally each brace is housed 1/2" under the actual size of the timber or to a standard "inner sized" timber. I haven't opened you last uploaded frame design to check your housings.
I'm not sure if they were there, anyhow.
Are your braces housed 1/2"?
What is your tenon length?
Normally brace tenon lengths are around 3" from the shoulder. If the post is a 8x8 and they are housed 1/2" that leaves 7" of post, with two 3" tenons you should have a 1" gap in between.
Of course if your posts are 7" wide then they may/do butt. And it would be a through mortise.
And you would naturally trim each brace tenon at least 1/8" so that the don't actually touch in the middle.
Brace tenon peg hole layout is normally 1 1/2" off the shoulder and 2" off the bearing end. And the peg hole in the tenon is draw bored in two directions. To pull and hold the joint tight.

Trying to cut by pass mortises will be a challenge for sure. Keep it simple and keep them in line. I vote butt or through mortise to make it easier.

Jim Rogers

[Ljohnsaw]

Thankls, Jim. So let me restate to see if I got it. The housing on the end of the brace is typically 1/2" smaller all the way around. My braces are 4x6 so my housing would be like 3x5. Now on the timber, the housing typically  goes in 1/2".  The tenon then "only" needs to go 3" beyond the housing. Did I get that right?

So, are my 4x6's too small and - should upsize to a 5x7?

My post are minimum 8x10 with some braces on the 10" direction so ther will be plenty of space.   So on the major beams, I'm not comfortable with a 1/2" housing and I made them 1" deep. Should they be 1-1/2" or 2"?  I'm worried about it shrinking and pulling out. I know I need to have enough surface area (including the tenon) to support the load.  The load carring capacity of the posts is amazing. The beam calcs give me that area and it suprises me how little is required.

In joining a 8" wide beam to a 8x8 post, should - reduce the housing like the braces?  If I don't, it just looks like the beam is sitting in a notch on the post. Poor form?

[Jay C. White Cloud]

John,

For the sake of this conversation about braces, I'm going to go over some points, (some probably redundant, sorry) that you make or may not see at this point.  One, I have stated this before, is you don't need the braces at all, or at least in an oblique orientation.  The oldest timber frames in the world still standing, (and subjected to millenia of earth quakes, and even a nuclear blast during world war two,) do not have any oblique bracing at all...anywhere.

Second, braces as you see them in vintage and contemporary vestiges of the vintage framing, only work in compression, no other way.  There is absolutely no reason to make them any bigger than what they are, or house them deeper.  Considering that most braces are 3x3, 4x4, 3x4, or 3x5, the larges ever being 4x6, (unless part of a truss system-that is a different thing) your are already way oversized to begin with, as they work in compression, (like a post,) they do not need to be that big, so your size is just fine.

Third point is the tenon is only there to really keep them from falling out of their mortise during raising.  Because of there oblique nature and the way wood behaves in shear, you can't get the tenons long enough to do what many believe they are doing...giving more room for a peg.  Again, traditionally and in "form following function" they work in compression and do not need to be peg, as the peg is really not doing anything for the strength of the joint and could actually be weakening it.  The better forms of this joint are compression wedged, not pegged. 

Jim description is 95% accurate in it's outline of the joint, other than the pegging and being draw born, this was never done.  The few turn of the century frames that started this practice, (we still only have theories why) present as failed 80% of the time, under examination while dismantling them. When the peg does do something, it appears to be during raising, holding the brace in place while the frame is raised, and in those frames, are smaller, 3/4" to in size.  We have even noted that in some of these frames, the connecting girt (beam) has the pegged section of the brace at the top, while the lower is held by a compression wedged on the bottom portion of the brace (sometimes under the tenon, sometime over) 

This has been a long running debate within the academic circles of timber wrights, to peg or not to peg.  When ever test are conducted, the pegged braces fail in relish of the tenon.  I would also point out, than many (most?) traditional tenons are only 2" to 3" long on average, maybe 3.5".  It was only in the later half to the 19 century that pegging came into vogue, my theory being we lost so much oral tradition during the civil war, that habits started to form that were based on assumption not good practice or instruction. Below is a short quote from a master timber wright, PE and historical Restorationist, Rudy Christian:

I find that barns built in the last half of the 19th century in Ohio are as likely to have pegged as unpegged braces.  My own engineering background temps me to believe that the carpenters were well aware that braces are meant to work only when they are being pushed on, or "in compression". That being the case, pegs were not needed, and in fact could work against the frame in certain conditions.

[witterbound]

First, if you're going to have all that framing for windows and doors, why don't you eliminate the braces on those walls and instead just use a straining beam at the top of the window or door?  I call them straining beams, not sure if that's their technical name.  It's where you drop a beam some distance from another, like you see in some Chinese timber frames.  Second, my frame sure wasn't stiff before we installed the osb on the outside.  I can't imagine that metal straps will add the requisite rigidity.  Maybe I'm I missing something.

[Jim_Rogers]

The housing on the end of the brace is typically 1/2" smaller all the way around.

No, not all the way around, only the post or beam has a housing on one side.
That is if you're using square rule edge layout. With square rule edge layout the housing is on the post or beam. The tenon is "bare faced" on one side.
Like this:



 

The housing looks like this:



 

Now on the timber, the housing typically  goes in 1/2".

The housing is measured from the layout side/reference edge at the arris of the timber so if the timber is truly an 8x8 then the housing is 1/2". But if the timber is oversized it is still draw to 1/2" under. If that is your "general frame rule".

When you design a frame you establish some "general frame rules" and these rules guide you to make all the joints correctly. And with every rule there are exceptions.
One exception is that the brace is not reduced in size.

If the timber is undersized the the housing will be less. It could be only 1/4". You have to understand where you "pull" your measurement from. You can't just take a rough sawn timber and cut a 1/2" housing in from the surface. It has to be laid out correctly from the arris regardless of the actual sizes of the timber.

The tenon then "only" needs to go 3" beyond the housing. Did I get that right?

Yes that is right.
Again there are exception to the rules. Another one would be if this was a "tension" brace. But as it has been mentioned most braces work in compression.

If you want a "traditional" looking frame then you would/could use the braces.

In 2002 I was involved with a guild project where we dismantled a barn build 15 miles north of Boston in 1856. Every brace in this barn was pegged. And there were lots of braces.

When we restored this barn, another part of this guild project, and raised it, we put in all the braces and pegs again.

are my 4x6's too small and - should upsize to a 5x7?

I have not opened/downloaded your frame design. Without looking I can't say for sure but most likely no. They should not be upsized unless your engineer says so.

Should they be 1-1/2" or 2"?

No, it is my opinion that they should not be made larger. Unless your engineer says so. Again, you could be spinning your wheels until your engineer gives you some details.
I do understand that you want to use "your" engineer. But if he doesn't have any experience in timber frame design engineering then you're paying for his education.
This is why we use engineers who are experienced in timber frame design and loads on these frames.

In joining a 8" wide beam to a 8x8 post, should - reduce the housing like the braces?  If I don't, it just looks like the beam is sitting in a notch on the post. Poor form?

I have not reviewed your frame design. Every design is different. Shrinkage is a concern for sure. You engineer will/should advise you if your housing are deep enough to create a shelf for the beam to sit on and hold the load. If he can't do that then hire another engineer who has experience with timber frame design and loads on them. You know who, you've already spoken to him.

Good luck and keep asking questions.

Jim Rogers

[jander3]

In joining a 8" wide beam to a 8x8 post, should - reduce the housing like the braces?  If I don't, it just looks like the beam is sitting in a notch on the post. Poor form?

For square rule, your timbers will be a over-sized for your joints.  To join the beam to the post you will have to taper the beam down to the housing dimension.



 

For knee braces to avoid the need to taper, I cut them over-sized on the saw mill.  Before cutting the braces, I plane the stock to exact dimension.

[Jay C. White Cloud]

Hi John,

First let me tell you that your questions are great, thanks for taking the time to ask them.  I gave you some feed back already about the braces, and want to stress to you, (if I sounded other wise,) that Jim's guidance is awesome.  Where he and I differ is only academic timber wright "stuff,"  Follow his guidance about the braces, if you are going to use them. (minus the pegs of course... :D :D :D)

Hello Witterbound,

Why don't you eliminate the braces on those walls and instead just use a straining beam at the top of the window or door? I call them straining beams, not sure if that's their technical name.

These are call "nuki beams" in Japan, and they have counter parts in most Middle Eastern and Asian framing.  Your use of "straining beam" is a little miss placed, but I understand why you would call it that, and it isn't really wrong.  A straining beam is part of a truss assembly, usually in covered bridges, but also the beam that spans the top of Queen Posts are called straining beams.  Most of the frames I facilitate  do not have oblique bracing, they are exactly as you describe, and yes very similar to China, or most of Asia.

I can't imagine that metal straps will add the requisite rigidity.  Maybe I'm I missing something.

The straps are great for stiffing a frame, and they make the PE's so happy.  As a traditional timber wright, I do everything in my power to do the frame as they had been done, but will add these straps afterwards because they do work so well, and it makes the PE math work much better.  In our frames with the horizontal bracing modality, we get the required stiffness the PE is looking for and the flexibility that the frame needs to endure time.

Hey Jim,

Didn't want you to think I didn't agree with your brace advice...it is really good. (minus the pegging of course. :D ;))  I agree, many, if not most frames after 1850 have pegged braces, especially in New England, but for the majority and prior to this time, it isn't true.  We had just been discussing this in Michigan frames and those before 1850, in most regions.  All the evidence, and engineering points to the peg as being useless if not actually weakening the joint, wedging is much better. 

Regards,

jay

[Ljohnsaw]

Jay/Jim,

Please take this the right way - I find your differences - and disagreements - amusing AND informative.  You both have your traditional ways that you would like to see kept alive - at least that's how I interpret your individual opinions.  What I'm striving for is to build a cabin to what my mind's eye sees and that would be the more North American style with big beams/posts and braces.  My goal is also to be "green" - maximizing the use of local materials (preferably from my land) and minimizing the use of processed  wood like plywood or OSB unless engineering necessitates it.

Jay,

I think I may have stated it before - while I do like the look of some of you projects, I don't have the time or resources (money mainly) to fight the engineering academia out here in earthquake-central! :D :  I want to build this cabin in MY lifetime, not may grand kids!

That being said, I see the merits of pegs to hold the frame together while lifting.  The joint itself provides the strength (in compression).  To me, personally, I don't see the peg providing much strength in tension as there is little relish to resist and the joint is not meant to be in tension.  When you mention wedges to hold the braces in place, I'm assuming you are sliding them in the top side of the joint, in-line with the brace - correct?  Use something like a 2x4 and a mallet to drive it in?  Given the shear number of braces in my plans, I'm all for using wedges vs. cutting so many pegs an drilling so many holes!!!!   I'd like to see a picture or even a drawing of this practice.

Now, as far as the square rule, etc.  I've got sort of a problem with my drawings.  Engineering the load, I need to use a 10x16 - so that is what I draw.  I know my beam won't be that exactly, I'll be sure to oversize it a bit when cutting.  In fact, everything that I cut I will add a percentage for shrinkage such that I will be over the stated size.  Should I draw my beams to be say 10.5 x 16.5 so the housing comes out right?  I chose not to do it that way.  Am I wrong?  My shop drawing will have all the dimensions for the cuts so do I bother with that fine point?  As long as I indicate the working face and adjacent face, all should be good, right?  It would be a relatively easy modification, but does it really matter? :-\

[Jay C. White Cloud]

I'll see If Don has any photos, maybe Rooster does.  Did the Engineer say you needed these big timbers, or is that just the look you are going for? Most often, if there shimmed/wedged, it is from the bottom (outboard,) as Rudy suggested, however with housed braces this may not be best aesthetically.  The other is wedging from the top, (inboard.) Which do you think you would like to see?

Regards,

jay